Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

[howardc64]

I would also be interested in doing a group buy of custom seals. I'd be in for at least 2

I'm interested in the custom seal too. 2013 model S P85 here that has 20k on the model q DU from 2020.

Ok, so thats 5 total interest so far. Would be good to get a Tesla independent with greater volume needs. Spoke with 057, sounds like they maybe interested in a source also. I'll gradually reach out to other shops.

Have you talked to Saint Gobain?

Have not. Looks like multiple people contacted but received no response.

[howardc64]

BTW, setup a website on rebuild build info directory on this LDU. Info is already on various forums and website services as an index directory. @Johan did majority of the contribution. Various projects here are linked.

https://sites.google.com/view/teslaldu/home?authuser=0

Gradually filing it up but lots of useful pointers already.

[asavage]

Got the following info in a brief phone call

- This application (Coolant seal on a 10k RPM shaft) likely will leak after some period due to amount of surface that is engage per time period (I forgot the term he used) with water/coolant media. Basically 10k RPM = a lot of surface is engaged in unit time.

"feet/minute" is the relationship I used in our email, which is how I think about it. Whether that's a term used in the seal interface engineering world, IDK.

Anyone interested in developing our own seal? For $1k, maybe we can get 15? seals. Anyway, say $75-$100/seal shipped.

Sure, I'll front the cost of two seals, in that price range.

On seal design, I was wondering if don't need the extruding lip on the dry side to keep oil/dirt out would make install much easier. Need to consult with seal designer of course.

When I read this, Initially I agreed that the dust lip isn't needed, but after reviewing Johan's YT vids I have changed my mind. While we're not supposed to have solids flying around in the rotor cavity, in practical terms it seems more common to have debris in the rotor cavity area than I thought.

Best practise for seal installation is using a sleeve (or sleeve-like material). In Ye Olde Days, we could get away with something like masking tape or similar, but for PTFE, the stuff is notoriously un-pliable and sometimes requires a specialized installation tool/method. My predominant experience with PTFE seals is in automatic transmissions, and power steering hydraulics. PTFE is denser than typical seal materials you see in other automotive applications, but is less pliant. I've used cone-shaped install tools to introduce the seal to the shaft, but that doesn't address moving the seal into position over retainer grooves, splines, etc. where a sleeve or wrap would be a best practice.

What I see from Johan's install pics is that the encoder wheel end of the rotor is installed into the coolant manifold: a blind cavity, with no possibility of using a sleeve. Therefore, the excluder seal lip, which faces/is formed toward the "wrong" direction, must be pre-conditioned prior to offering up the manifold to be installed. The PTFE seal materials I've worked with can be deformed without damage within a very limited range, and I propose using both mild heat (say, ~150°F) plus a circular expansion tool of some kind -- there are several -- to temporarily pre-form the excluder lip to be slightly larger. As it's not meant to be a rigorous seal, we are not concerned with a perfect fit, and this seems reasonable.

[howardc64]

"feet/minute" is the relationship I used in our email, which is how I think about it. Whether that's a term used in the seal interface engineering world, IDK.

Sure, I'll front the cost of two seals, in that price range.

Thanks. Indeed, it was something like feet/min. Basically amount of surface area over time period which makes total sense.

So now we've got 7 seal interest which is great. However, been thinking more on doing own seal design....

- The most important factor is probably seal material (PTFE blend) and proper shaft surface roughness prep for this application (sealing water/coolant media over stainless steel shaft under 10k RPM rotation dynamic condition) There are various PTFE additives that yield different key seal properties (friction level and extrusion resistance)

- The PTFE seal will wear sacrificially. And a lipped design is desirable to maintain feeding pressure and material to the shaft surface. Shape wise, I'd imagine an experienced PTFE seal designer should know the proper lip curvature and how much lip diameter need to be smaller than the shaft to produced the right pressure+fit to seal the thin viscosity media.

- Tesla appears to have revised the seal design over last 10 years of Model S production. But seemingly have not achieved any substantive results as LDUs still leaks with regularity.

- Another note is the natural and perhaps underrating parts from aliexpress (Chenming seal) I worked for a Japanese tech company for many years. The natural communication barrier between English speaking engineers and their non fluent English speaking counterpart often results in unnecessarily lower confidence in those less fluent (but quite natural since English speaker has no data to go on) Johan texted with Chenming seal supplier and their reply shows some degree of expertise. Wasn't just a no info black hole.

With this reasoning, I'm not sure developing our own seal is any better result than Chenming's seal. First order problem is the application and probably no seal will prevent slight leaks. Next order of business is probably eliminate accumulating coolant volume near the high speed bearings and further collateral damages. So necessary to periodically replace sacrificially worn seal material and resurface worn shaft face.

Finally, to truly evaluate a seal's performance, Probably best to have a LDU test jig setup for rapid change and test instead of in vehicle application with far greater barrier to seal change.

So I'm debating to just use an existing triple lipped seal (older Tesla OEM if can find one) or Chenming and use Johan's shaft surface roughness prep technique in his video (600->1500 grit sandpaper belt over spinning shaft)

[SuperV8]

Thanks. Indeed, it was something like feet/min. Basically amount of surface area over time period which makes total sense.

So now we've got 7 seal interest which is great. However, been thinking more on doing own seal design....

- The most important factor is probably seal material (PTFE blend) and proper shaft surface roughness prep for this application (sealing water/coolant media over stainless steel shaft under 10k RPM rotation dynamic condition) There are various PTFE additives that yield different key seal properties (friction level and extrusion resistance)

- The PTFE seal will wear sacrificially. And a lipped design is desirable to maintain feeding pressure and material to the shaft surface. Shape wise, I'd imagine an experienced PTFE seal designer should know the proper lip curvature and how much lip diameter need to be smaller than the shaft to produced the right pressure+fit to seal the thin viscosity media.

- Tesla appears to have revised the seal design over last 10 years of Model S production. But seemingly have not achieved any substantive results as LDUs still leaks with regularity.

One of a seal's critical design criteria is its max surface speed in meters/sec (m/s) (or ft/min for US) RPM's need to be used in conjunction with diameters.
From SKF;
larger diameter shafts can accommodate higher circumferential speeds than shafts with smaller diameters. This is because the cross section of the shaft does not increase linearly with the increase in diameter but by the square of the increase in diameter. Therefore, the heat dissipation of a large shaft is much better than that of a small shaft.

[howardc64]

One of a seal's critical design criteria is its max surface speed in meters/sec (m/s) (or ft/min for US) RPM's need to be used in conjunction with diameters.
From SKF;
larger diameter shafts can accommodate higher circumferential speeds than shafts with smaller diameters. This is because the cross section of the shaft does not increase linearly with the increase in diameter but by the square of the increase in diameter. Therefore, the heat dissipation of a large shaft is much better than that of a small shaft.

All make sense. However, the rotor's shaft locks in 30mm diameter and ~8mm seal width so these can't be changed. Only remaining design variables are material + shape + shaft surface prep.

[muehlpower]

All make sense. However, the rotor's shaft locks in 30mm diameter and ~8mm seal width so these can't be changed. Only remaining design variables are material + shape + shaft surface prep.

That's not true. There are twist-free ground rings for use with sealing rings. I hope google translates this correctly.
IR30x35x16-EGS or IR30x35x12.5-EGS

[SuperV8]

All make sense. However, the rotor's shaft locks in 30mm diameter and ~8mm seal width so these can't be changed. Only remaining design variables are material + shape + shaft surface prep.

You had a question previously following your conversation with a seal supplier - I was just trying to help.

A 30mm seal at;
10,000 rpm has a surface speed of 15.7m/s
15,000 rpm has a surface speed of 23.5m/s
18,000 rpm has a surface speed of 28.3m/s

Limit the LDU to 10k and just looking at m/s it looks like a good Fluoro rubber seal is suitable.

However it gets more 'complicated' as I would think 1,2 & 4 conditions below also apply to the LDU;

The values obtained from the diagram 4 should be reduced if:

1; radial shaft seals with an auxiliary, contacting lip are used
2; lubrication is inadequate or grease lubrication is used, i.e. when underlip temperatures increase due to poor heat dissipation
3; the counterface does not meet surface finish or running accuracy requirements
4; there is a pressure differential across the seal

from here:
https://www.skf.com/group/products/indu ... ble-speeds

[howardc64]

That's not true. There are twist-free ground rings for use with sealing rings. I hope google translates this correctly.
IR30x35x16-EGS or IR30x35x12.5-EGS

Interesting. Another mod to consider if increasing shaft diameter helps to reduce leak.

You had a question previously following your conversation with a seal supplier - I was just trying to help.

A 30mm seal at;
10,000 rpm has a surface speed of 15.7m/s
15,000 rpm has a surface speed of 23.5m/s
18,000 rpm has a surface speed of 28.3m/s

Limit the LDU to 10k and just looking at m/s it looks like a good Fluoro rubber seal is suitable.
image.png

However it gets more 'complicated' as I would think 1,2 & 4 conditions below also apply to the LDU;



from here:
https://www.skf.com/group/products/indu ... ble-speeds

Very helpful. Thanks

====

I'm quickly realizing to make any of these design choices, running it on a test jig is highly desired and evaluate. Quite an install/uninstall effort (at least on a Tesla) to change out a seal. Without design eval, can only gamble based on manufacturer knowledge and experience.

[Johan]

@SuperV8: Thanks for that graph!

Increase of the shaft diameter is probably not a solution in this case. Here's why: Start with the requirement that the LDU must sustain a continuous maximum speed of for example 100 mph (161 km/h). This corresponds to 11479 RPM, given an assumed tire diameter of 724mm and a given fixed LDU gear box reduction factor of 9.73. The graph below shows that at a given shaft diameter of 30mm, a fluoro rubber seal results in a maximum of 12420 RPM* (blue dashed line), so the 100 mph requirement is satisfied. Next, the graph shows that an increase of the shaft diameter to 40mm results in a reduction of the maximum RPM value from 12420 to ~11000 (red dashed line), so now the requirement is not met anymore. Also the addition of a sleeve introduces a thermal contact resistance between shaft and sleeve, which would lower thermal conductivity in shaft radial direction, which is not what you want.

*assuming oil or grease lubricant, which we do not have; equals the spec of HMS 5 seal

[howardc64]

Hey guys, I'm not going to pursue the build own seal route. Just not setup for it. Tesla LDU removal and reinstall is a bear at DIY home garage so no real easy way to repeatedly test and evaluate. A bench test setup able to run LDU is probably much better candidate. I'll put all info below if someone want to pursue.

https://advanced-emc.com/

Google "PTFE seal manufacturer" and their ad pops up on top (so they know how to get net traffic haha) zoominfo (probably limited accuracy but approximate) shows its a small company in Tulsa OK.

https://www.zoominfo.com/c/advanced-emc ... /356575497

Their website is full of PTFE seal info including this page on PTFE material blends (page is for spring energized seals)

https://advanced-emc.com/spring-energized-seals/

Cold called a couple of weeks ago and the president answered and provided all the info on my 9/6/2022 9:50pm summary post ( viewtopic.php?p=45021#p45021 ). Some additional useful info

- They bid on Tesla LDU coolant seal business a few years back. Lost on price. Not surprising given smallish company. Sounds like went through the design effort.
- Says they makes other seals for Tesla. Not sure what model and what seal. Didn't discuss.
- Asked about shaft material, assumed it might be stainless steel during short call.
- Familiar with the LDU coolant seal leak problem

So I'll leave it here in case someone want to pursue. I thought $500 min / 4-5 seal run wasn't out of the DIY budget and probably quite a bit better with a larger run. Called 057 said they were interested in seal source if there is one. They send the LDU rebuild out as does Gruber motors (haven't found their LDU rebuilder) And of course QC Charge does LDU rebuilds all day but not giving our seal source info.

Anyway, for a commercially viable effort to do the design and test, probably not worth it just for seal sale profits. So need to get bigger returns like rebuild business which results in restricting seal sales. To truly deliver a new designed/tested seal source to broader community, I think has to be DIY non profit effort.

I'll probably go with a chenming seal or Tesla old stock triple lip sal (have a source but sounds like very limited supply)

====

BTW, tech from QC Charge on teslamotorclub said he sees leaks often in lower mile LDUs than higher (mine Rev Q was 5 years 32k miles). This suggest failure mode may not be during rotation but perhaps parking or reverse. He guess the seal may be more "stuck on" after parking...

https://teslamotorsclub.com/tmc/posts/6169506/
https://teslamotorsclub.com/tmc/posts/7025439/

====

Been asking myself.. .any other solutions? Here is an idea... but just an crazy ideal with lots of mods

- Cool the rotor shaft with oil
- Require modding the coolant neck the seal is mounted on (split coolant to rest of LDU : windings/inverter and oil for rotor)
- Add heat exchanger for oil and coolant (matured tech)
- Need an oil pump solution for circulation (matured tech but no easy mechanical drive tap here. Don't know if tapping that little gear sprayer pump provides sufficient flow and just use the gear box ATF as coolant. Electric pump would need to find power source)

Anyway, kind of crazy mod but maybe get more rear/front main seal lifetime profile. Of course testing with both oil and coolant requires cleaning in between. Once again, best for someone with a bench test jig setup.

[howardc64]

Open up my 5 yr/32k mile reman Rev Q LDU. Found the following

- Same single lip coolant seal in stainless steel cage (leaked since I saw speed sensor with coolant)
- Coolant pooled just below the big inverter connector. Luckily didn't get very far and haven't damaged the inverter
- Found reasonably amount of magnetic mud in the gear box. All 6 bearings on 3 shafts have a little bit of play between inner and outer ring that I'd imagine is naturally present even when new. No visible fluting on bearing ring surfaces... can't really see the raceway
- Where primary shaft goes into the bearing on the inverter side of the case has brownish streaks.
- Found tiny scrape marks on diff gear
- Can't get my rotor out of the splined end

Here is more detail on all these

Seal and Shaft

Used Johan's method of removal Seal cage surface seems safe enough and mine had a bead of RTV on the bottom gap of the seal.

IMG_2621.jpeg

IMG_2667.jpeg

IMG_2668.jpeg

IMG_2666.jpeg

More pic+info here. Crossposted from teslamotorclub.

https://teslamotorsclub.com/tmc/threads ... st-7052908

Coolant in Inverter

Coolant pooled just below the inverter connectors. Slightest wicking started on the lowest wire bundle. Caught it just in time. No inverter errors yet. Coolant doesn't leave a trail heading to the lowest point. It could even be vapor travel + condensation mechanism.

I did feel sticky residue on bottom between inverter casing and gear box housing seam. And see/feel sticky residue on the windings just below the seal. So pretty obvious this is leak source and not inverter internal coolant channel (I hope)

Pic and info at 3 sequential posts in this link.

https://teslamotorsclub.com/tmc/threads ... st-7052908

Mud on Magnets

Fair bit of mud on big magnet next to oil pickup screen. Mud on fill and drain plug of course

IMG_2639.jpeg

Don't know the source as all gears and bearings look reasonably good. Bearings have slight play between inner and outer ring as might be expected even when new.

Primary Shaft brown streaks

Found brown streaks on primary shaft surface and inverter side bearing inner ring surface where it mates to. Reasonably smooth and the tiniest score with fingernail feel. No idea if was there after reman or occurred during my 32k miles.

I do have a light whine that sounds like engine braking under regen load going downhills at 20-30mph.

The primary shaft just slips into this bearing pretty easily (true in every disassembly video). Was wonder if when punching the accelerator to launch the vehicle (which I've never done on this LDU, did on older ones that got swapped out) wouldn't the momentum cause this shaft to ever so slightly slip against the inner bearing ring? No idea, everyone else's surfaces looks clean here.

The primary shaft bearing on the rotor side had to be tapped out (alternating side by side)

IMG_2651.jpeg

IMG_2650.jpeg

Diff gear teeth scrape marks

Not on the match teeth on intermediate gear. I'm guessing something was on the plastic shield just under the diff gear with big magnet just below holding it in place.

IMG_2658.jpeg

IMG_2659.jpeg

Can't Get Rotor out

Everyone else just pull their rotor out once coolant end cover and primary shaft are removed. Mine won't come out on the splined end. In fact, when pulling the coolant end cover, it pulled out the reluctor ring with it since rotor doesn't want to come out. Tried a little rotation and pull in case keyed. No luck. Tried tapping it on splined end (probably shouldn't have done that and risked damage to silicon nitride bearings) No luck.

Anyone encountered this before? Maybe Rev Q has a circlip behind the primary shaft seal? Or inner rotor bearing is stucked on the cup with something which would unfortunately probably mean destructive removal...

IMG_2662.jpeg

If I put coolant cover back on and bearing on that side seated properly. Rotor turns fine (but have a little scraping noise per rotation. compare to before rotor removal attempt. hopefully I didn't damage the inner bearing when trying to tapped it out... but maybe I did )

More bearing and cup pics

Remaining bearing and cup pics for reference

https://photos.app.goo.gl/PDVhD6pyaXKuHY159
https://photos.app.goo.gl/NdAw8VBfqJxHhh1K8
https://photos.app.goo.gl/5ALj4VHw7dznVfKW9
https://photos.app.goo.gl/GE94XqE7wgH9SBM59
https://photos.app.goo.gl/ubpXyjnKjLUuLJn57

[Boxster EV]

Can't Get Rotor out

In post two of this thread I describe how I removed the rotor. Method is Heath Robinson but works.

[howardc64]

In post two of this thread I describe how I removed the rotor. Method is Heath Robinson but works.

You dropped it on the coolant shaft? Thats what would happened if dropped it with inverter on top and motor on bottom. Wouldn't that press the rotor/bearing in more? Or maybe it will crack it loose.

Or are you dropping the edge of the motor case on wood and let the shock + momentum loosen the rotor to come out. In which case, the windings most likely took the landing as they extrude out slightly from the pretty thin case lip. Is that safe on the windings?

====

Got this tip from a LDU rebuilder...

Often times the bearing has a tight enough fit in the spline end that the only way to get it out is to disassemble the gearbox and either use a hammer and punch, or a large press to remove the rotor from the case. If you get really unlucky, the rotor will come out, but leave the bearing stuck in the case, which is quite difficult to remove and generally takes a specialized puller that can fit in that tight space...

====

My setup at the moment

IMG_2670.jpeg

IMG_2671.jpeg

Lets hope I don't destroy the inner ceramic bearings and/or have the bearing stay behind.

[Boxster EV]

My setup at the moment

https://photos.app.goo.gl/bLk8ut9ZBYKDt7DX8
https://photos.app.goo.gl/2szAt6ZSzLzh7wWa9

Lets hope I don't destroy the inner ceramic bearings and/or have the bearing stay behind.

That’s basically it. It’ll just require a shock / jolt to release the spline. The outer wood blocks will make contact with the motor casing, allowing the rotor’s vertical momentum to fall further and break free. Just ensure there’s something there to catch the rotor’s fall and not damage anything.

[howardc64]

UPDATE (1/3/2023)

The rotor can be stuck by the rotor bearing on the other side (towards the gearbox) having rust in the mating surface to the sleeve/bore on the stator housing. It is not necessary to open the gearbox (and disturb the gear train if no evident noise) If something can grab onto the outer rotor bearing or the thin "bearing stop" on the rotor shaft, it maybe possible to pull it out. There are no circlips or other mechanical means to hold the rotor in other than rusted bearing face against the sleeve. Here is a pic

download/file.php?id=18594&mode=view

The orange o-ring is between the rotor bearing and the bore. Some LDUs have this o-ring and some do not. This is all that is holding in the rotor and normally should just slide out if bearing face and sleeve aren't bound by rust.

Onto the original post.

=====

Got rotor out. Used a big sledge hammer (don't have 5lb hammer atm). 6"-8" drop on 13mm impact socket on top of the spline end rotor shaft. 2x tap and rotor came out with bearing (phew...)

68534340084__6EFE7A44-E313-4BC0-802B-9EA5A5F1CE51.jpeg

Quite interesting inner bearing has rust on outer ring (I think rust area is extended beyond the metal sleeve the bearing rides on) and doesn't spin as well as the outer where the leaked seal was... And rotor shows corrosion towards inner seal. So coolant attacked the inner more than outer in my case. Perhaps its leveling of my garage? Seems usually the other way around in most LDU leaks. If parking level decides where coolant pools, then it makes sense to tap drains on both ends of inverter chamber (not sure if and where to tap drain for motor chamber without damaging the cooling channels other than the reluctor chamber).

IMG_2677.jpeg

IMG_2675 (2).jpeg

IMG_2674 (2).jpeg

UPDATE (9/30/22)

Regreased hybrid bearings. The spline side (it took the hammer blow to get rotor out) have random light popping sounds spinning the rotor at low speeds. Perhaps damaged from hammering it out (or worn from grease turning into gunk). Ceramic bearings are used by bicycle racers. Here is a video comparing poor and high quality ceramic balls. Hammering the rotor shaft through the stuck bearing outer ring from above probably damaged the softer races



The rotor ceramic bearings are $$100+ to 400/ea for genuine high quality SKF depending on your source (see signature link) I think there is a way to hammer out the stuck bearing safely on the outer ring face. Would need to destructively pull out the gearbox seal (towards gearbox), probably remove circlip, slip a pipe around the outer ring to tap it out. I think QC Charge just pound out via shaft since they were replacing the ceramic bearings anyways.

Just didn't know what was between the bearing and seal. The supposed grounding ring appears to have been designed out of Revs for awhile now (see rev difference table in signature website)

[howardc64]

Did a follow up call with Advanced EMC the PTFE seal maker. Got a little more insight on what is involved. There are probably 2 main barriers

1. Design + Test

Design choices are mostly from knowledge and experience of PTFE material blend selected against shaft material (base material, hardness treatment etc) Systematic engineering would suggest to test a new seal on a jig, observe, measure and evaluate results. Test process probably cost $5-$6k and a month time (EMC has shops they work with). Should at least do this before putting it in a car (or bigger jig like a bench rigged LDU)

2. Tesla's history of feast and famine parts availability

I've seen this scenario before where pioneering solution providers with good business gets taken out overnight when Tesla decides to release a solution. Model S's 17" screen's software was over logging and wearing out the flash memory. Some DIY folks worked with phone data recovery expertise to remove old flash, read data, read data with a socket, write to new one, solder back onto the system for $500. Tesla took out this business overnight when NHTSA forced them to replace these systems. 17" screen controls pretty much most of car's functions. While the car can drive without it, NHTSA considered it safety. So whoever fronts the cost and energy to develop this seal need to take the risk sales gets vaporized if Tesla is triggered by some reason to react (say a bunch of post warranty MS owners screaming bloody murder in tech social media). Us DIYers don't lose much. A business like a seal maker has more to consider.

Its understandable why QC Charge don't give out their seal source. Not much $ selling seals compared to rebuild. And even the rebuild business is at risk of Tesla deciding to extend warranty (not holding my breath) on LDU. Unfortunately seal replacement rebuilds capacity can't scale and become distributed geographically if seal is not even available to independents or DIYers. Such is Tesla's DNA : High vertical integration which comes with high HQ control.

So these are the barriers to getting something done. #1 is perhaps the first initial barrier for us DIY crowds.

====

As a side note, this company was working with a tier 2 supplier to Tesla on what appears to be a "find a seal that don't leak" evaluation. They made several and all leaked. Sounds like all seals from all suppliers leaked. EMC ultimate just stopped investing because it looked like an endless exercise. We know reasonably sure what ever seal Tesla chose is still leaking and perhaps even quicker. Most seal experts would conclude leak is inevitable in this application. Empirical evidence from Tesla owners suggest similar (lots of LDU changes under warranty including leaks) Chenming is a well known Chinese PTFE seal maker (EMC knows of them of course) Maybe was a manufacturer in the sourcing competition. Did the test design and I think we have no evidence Tesla is using it. Then the incredible broad Chinese supply chain capability provided a solution ( aliexpress ) to meet a demand. Don't know if thats the case but could very well be.

Hope this helps.

[howardc64]

Looks like my Rev Q reman LDU has no grounding ring on the shaft. Here are some pics

IMG_2680.jpeg

IMG_2715 (1).jpeg

IMG_2712 (1).jpeg

IMG_2740.jpeg

BTW, the only grounding brush I've been able to find on a LDU (rev F) is from here.

https://teslamotorsclub.com/tmc/threads ... ix.145078/
https://photos.app.goo.gl/a2hND1uF3e355Bs69
https://photos.app.goo.gl/Yd5VFsPQiBUWbSDP6

Additional damages

Primary shaft

Have brownish streaks on surface to the inverter side bearing surface (also has brownish streaks). Bearing doesn''t seem worn.

IMG_2651.jpeg

IMG_2650.jpeg

No fretting inside the raceway of both bearings on the shaft

My working theory now is the streaks obviously suggest slipping. But has to be rare or this highest speed shaft would burn up that bearing quickly. The surface is not press fitted to the shaft and has no lube passages. Perhaps under high momentum changes, it just slips a little?

I see same in other teardowns

- Johan's teardown (also with brownish streaks)
- JetBoat guys's teardown
- Boxster EV's teardown




download/file.php?id=13419&mode=view

Probably acceptable damage according to the design. QC Charge said they always replace 2 bearings whenever opening the gear train. I'd assume its the 2 on primary shaft given they are the highest speed.

Intermedia Shaft

Motor side bearing (I think load side) outer ring face and cup has these marks on there

IMG_2643.jpeg

IMG_2642.jpeg

No fretting inside the raceway of motor side bearings and rollers on the inverter side bearing.

My working theory is there is enough axial play on this shaft to score the bearing's outer ring face and the cup periodically say under load. This loadside bearing is not press fitted. Amount of play is governed by intermediate shaft length, depth of the press fit bearing onto the shaft. non press fitted roller bearing on the other side and 2 halves of the gearbox assembled by RTV+bolt. Seems like some variation in play is inevitable.

Johan's teardown has same marks on the cup (and I presume the mating bearing face as well)



Probably acceptable damage according to the design.

Metallic Mud

This gearbox has 10:1 ratio. Starting with high RPM motor all the way to driving the half shafts. Its a wide range to trade off efficiency (thinner ATF) to high wear protection (multi weight gear oil for rear diffs such as 80w-90) LDU also has no damper for the applied torque (ICE's gradual torque curve, torque converter/clutch/clutch packs) Tesla went with thin ATF for efficiency on a 10x ratio gear box. Seems like less wear protection is the required tradeoff.

For reference, FWD ICE automatics are usually 0.5+ to 3-4x ratio and motor RPM at 1/2 to 1/3 of Tesla LDU at highway speeds. Much less aggressive ratio to use ATF. Some automatic gear boxes use thick multi weight gear oil for final diff gears (which change speeds at every turn)

I think this suggest a higher gearbox oil change frequency. Since its only 1.5 qt of Dex6 ATF and there is ample mud at 32k on my reman RevQ. Probably worth changing it annually along with speed sensor and inverter B+ B- port checks for coolant leaks. However, the big magnet next to oil pickup tube captures so much mud that ATF change probably doesn't get any of that out. Only cracking open the gearbox can do that.

[asavage]

There are several layers of defence we can apply to the overall coolant leak issue. Replacing the seal et al will (usually, supposedly, temporarily?) stop coolant ingress. Great, problem solved . . . for now.

Based on historic trends, we're making a reasonable assumption that the rotor seal will leak again. We can put in place protective measures to slow the damage caused by a repeat incident.

I think that the mods that Johan performed on his repair are fine, and I like that he walked us through his assumptions and reasoning. Most of the screengrabs below are from one of his excellent YT vids on this topic.

Possible defensive measures that could be incorporated into a seal repair process include:

1) Seal off the rotor side from the inverter side.
Alex @ QCP says that he installs a silicone gasket there to replace a paper gasket (not clear to me what that means) and then uses Form-A-Gasket (a Permatex-branded RTV [Room Temperature Vulcanize] silicone-based sealant), to fill that cavity. I think RTV would work as well as Johan's two-part potting compound, though it might not look quite as nice

The separate 4-wire bundle needs its own, separate application of sealant as well, I think.

One problem that arose during Johan's assembly was that a jig is probably needed to hold the bus bars in the proper position, prior to potting using his pour method -- and probably is a good idea using a caulking-style silicone injection method. He found slight misalignment of the bus bars with the inverter connector locations during assembly, a very easy thing to overlook. The bars/connector pads misalignment shown below is not parallax error, and Johan had to persuade the bars to move to the correct locations, possibly compromising the potting material's seal.

So, a jig.





2) Create a weep hole under the seal, to dump overboard seal leakage right at the first leak point.
Funny, back in the day, every automotive water pump had a weep hole between the coolant seal and the pump shaft bearing.

On the Tesla LDU, installing a weep hole is a well-trod path that others have done successfully. Drain line or not -- and if so, the type of fitting -- are a preference/optional item, but just providing a safer place for leakage to exit is a very good start:

3) Create a weep hole/inspection hole/sensor hole in the bottom of the stator housing.
This is a hole at a low point in the rotor cavity, where a one-wire sensor can be installed in a eg 5mm hole, to provide an in-car warning annunciator (light, buzzer, SMS msg, etc.); or, it can be used as an additional drain point.

AFAIK, this was the first documented drain location/method for an LDU.

https://www.myrav4ev.com/forum/viewtopi ... 419#p29419
https://www.youtube.com/watch?v=ps2gha4w5YE[url]

4) Seal the existing vent balance hole on the rotor end support (between reluctor chamber and rotor cavity), and install a second external vent, Toyota 33197-0R010 (USD$8 ea.). Aerosolized coolant that being whipped about by the reluctor is thus slowed from moving through the OEM vent hole to the rotor cavity, giving it time to find its way to the weep hole that was installed:

5) Add a third external vent to rotor end support, between rotor cavity and outside:

6) Add an inverter-side drain.

I'm of two minds on inverter drains.
QCP is selling their "drain kit" that taps the inverter side. But, I've read no evidence that coolant leaks have ever started on the inverter side, but there seems to be at least one instance where the gearbox lubricant escaped to the inverter. So, while I'm not particularly worried about monitoring the inverter side for coolant, coolant in the inverter isn't the only thing that needs external validation

7) Less damaging coolant.
An idea that has been brought up is to discontinue cooling with a water-based coolant (ie use oil, or a glycol-based waterless coolant). Internal leaks would then cause less immediate, and less expensive, damage, giving more time for a leak to be detected. Using waterless coolant will make electronic detection of a leak challenging, as the current leak detection schemes are either conductivity- or vertical-level based. Is there an electronic glycol detector?

[asavage]

Looks like my Rev Q reman LDU has no grounding ring on the shaft.

BTW, the only grounding brush I've been able to find on a LDU (rev F)

Yeah, it seems that Tesla dropped installation of the Aegis ring at some point. Multiple reports of Tesla-supplied reman units have none installed, so it's not just 3rd-party shops or DIYers leaving them out.

Metallic Mud
[ . . . ]
I think this suggest a higher gearbox oil change frequency. Since its only 1.5 qt of Dex6 ATF and there is ample mud at 32k on my reman RevQ. Probably worth changing it annually along with speed sensor and inverter B+ B- port checks for coolant leaks. However, the big magnet next to oil pickup tube captures so much mud that ATF change probably doesn't get any of that out. Only cracking open the gearbox can do that.

Ferrous material on the three magnets means that's ferrous material not in solution, and it's therefore not harming anything. There's no need to remove it or clean the big magnet, but as you noted it's also not going to come out with an oil change. Cleaning the fill/drain magnet(s) is OK, but there's plenty of magnetic surface to take the bits out of the moving lubricant, even with a thick coating of particles.

Now, what's causing all this loose ferrous material, and does that need addressing, those are different concerns, but I wouldn't worry a bit about removing what's on the magnet. To me, on an uncomplicated gearbox like this, that seems like a lot of particles. I sure want to point my finger at the rotor's pinion gear, because that's where things are moving fastest, and where stray induced currents could be, but I don't have the education to back up my guess.

Oil Change Interval (OCI) is a hot topic everywhere, like your favorite brand of oil/spark plug/coolant. I will note here that anybody's ATF is going to be pretty darned good quality these days, it's pretty much all synthetic -- which, done right, means the oil molecules are built-up from natural gas base stock, so no crud or incomplete chains in the oil to being with -- and ATF is specified for some of the most demanding applications you'll find outside of aerospace.

ATF doesn't have a lot of HD EP qualities, but it holds up in planetary gearsets in 1000+ HP drag cars (I know, I know: Apples to Oranges) and I do not doubt that little degradation takes place in the LDU's ATF, even if you doubled the OCI. Typically, either overheating or foaming plus overheating are the only ways to seriously degrade ATF. Additives . . . maybe. Anti-foaming agents probably are not forever, and foaming is a real possibility in this box.

EP is needed in the diff gears, but usually isn't for planetaries: there's almost no wiping action going on, nothing comparable to typical RWD hypoid gears, for example.

Note that Tesla does have a externally serviceable filter on their later DU designs, so they think it's needed. Oil is cheap, and any oil change monkey can do the job, so it's not expensive to have done. So, sure, change the oil frequently, it's not hard to DIY, or it's not expensive to have done for you. But I won't lose any sleep over having a 50k OCI on it, even if it's only 1.6l. It doesn't cook in the LDU.

[howardc64]

]Yes, drain and coolant containment mods per Johan (in touch and following his directions) and others are on my next work item now that my reman Rev Q LDU is fully disassembled. Just sharing gear, bearing, and mud observations. Non seem to be first order problems (except the rotor bearing's grease ruined by coolant)

I'm considering additions to Johan's drain+vent mods based on observations

- On sealing off bus bar tunnel, rotor half of the gearbox casing has a 2.5mm inset to accommodate the useless paper gasket Tesla installed. Inverter side 1/2 of the case is flat forming a slot for a silicone gasket once closed (Cut holes for bus bars+temp sensor cable + RTV to seal). However the inset lip is quite small above and below the bus bars but RTV probably seals up everything after gearbox case is mated. Sounds like this is the QC Charge mod.

IMG_2751.jpeg

IMG_2750.jpeg

IMG_2749.jpeg

But need to consider if silicone gasket accidentally gets beyond the inset region and prevent the 2 halves from sealing properly...

- On my LDU, coolant pooled on the connector side of inverter housing and attacked the inner rotor bearing more than outer. Rust pattern on rotor+ stator also suggest inner side pooling. So my garage floor and/or LDU/subframe probably tilts ever so slightly towards one side (passenger for Tesla LDU). Probably good idea to tap inverter casing near the gearbox side as well. QC Charge taps 5 drain ports total (didn't say where) but I'd imagine inverter casing got at least 1 on each end. Would be nice to tap drain on rotor side too but need to know where to avoid damaging the stator cooling channels (haven't figure out where yet) But yes theoretically coolant should never be there after reluctor chamber drain+hole closing+vent mod + closing off bus bar tunnel. But given the small gap between inverter electronics and its housing, probably worth doing just in case coolant makes in somehow.

It is also clear that if the owner isn't say too sensitive to slightest noise changes, inverter electronics could be taken out before motor side provide any noticeable warning. So during 6mo/annual speed sensor leak check, good idea to pull the B+ B- cover to see any coolant (mine had tiny drops behind the o-ring) and nuts to see if dirty from all the coolant gunk accumulating.

Thanks for note on ATF. Was just surprised at level of mud on 32k miles so thought about the mechanism. QC Charge said not uncommon to see 1-2mm mud on fill+drain plug magnet which means the big magnet near the oil pickup screen has a lot more.

Let us know what you find with less corrosive coolant experiment

[asavage]

I ordered a single gallon of Evans waterless coolant, which will arrive early next week. The PWM doo-dad will arrive . . . today, Amazon says . . . [goes out and checks mailbox] . . . yup, got it.

I wonder where I put that Tesla coolant pump . . . found it, in the "RAV4 EV" tote.

[Unscrews cover]

Ugh. I should have pulled the impeller cover off before: the impeller is hard plastic, no chance of this being adversely affected by high-viscosity coolant.

[SuperV8]

I ordered a single gallon of Evans waterless coolant, which will arrive early next week. The PWM doo-dad will arrive . . . today, Amazon says . . . [goes out and checks mailbox] . . . yup, got it.

Personally I'm not a fan of 'waterless coolant' It has a lower heat capacity than water meaning for your same pump speed and radiator size your motor/inverter and what ever else gets cooled will be running at a higher temperature.

[SuperV8]

This gearbox has 10:1 ratio. Starting with high RPM motor all the way to driving the half shafts. Its a wide range to trade off efficiency (thinner ATF) to high wear protection (multi weight gear oil for rear diffs such as 80w-90) LDU also has no damper for the applied torque (ICE's gradual torque curve, torque converter/clutch/clutch packs) Tesla went with thin ATF for efficiency on a 10x ratio gear box. Seems like less wear protection is the required tradeoff.

For reference, FWD ICE automatics are usually 0.5+ to 3-4x ratio and motor RPM at 1/2 to 1/3 of Tesla LDU at highway speeds. Much less aggressive ratio to use ATF. Some automatic gear boxes use thick multi weight gear oil for final diff gears (which change speeds at every turn)

I think this suggest a higher gearbox oil change frequency. Since its only 1.5 qt of Dex6 ATF and there is ample mud at 32k on my reman RevQ. Probably worth changing it annually along with speed sensor and inverter B+ B- port checks for coolant leaks. However, the big magnet next to oil pickup tube captures so much mud that ATF change probably doesn't get any of that out. Only cracking open the gearbox can do that.

Not sure I understand your point here regarding ratios?
The Tesla 9.7344:1 gear reduction is total gear reduction including differential reduction gear ratio.
The 3-4:1 you mention for the ICE auto transmission is NOT including any final drive gear reduction. Many ICE drivetrains can have 10-15:1 total gear reduction in the 1st & 2nd gears.

ATF is/can be a very high quality oil - generally much more expensive than any MTF made from better quality oil base stocks.
Rear differentials are hypoid gear and have totally different oil requirements than front differentials in transverse ICE cars - which is why they need different/separate oil. Transverse transmissions are quite happy to share their oil between the reduction gears and the differential.

[asavage]

Personally I'm not a fan of 'waterless coolant' It has a lower heat capacity than water meaning for your same pump speed and radiator size your motor/inverter and what ever else gets cooled will be running at a higher temperature.

Lots of people are not fans of waterless coolants for that reason: with water being "1", glycols typically have a thermal capacity of around .68-.72. In the ICE world so very many people seem to be chasing cures for overheating, and waterless coolant just isn't the right fix for almost all those situations, so it's gotten a bad rep.

However, in the LDU I don't think we need a whole lot of heat-moving capacity; there's just not a lot of heat to be moved, and unlike a legacy ICE situation, the pump capacity is not limited by the idle speed of the ICE; Tesla's thermal management can push the fluid as fast as is needed regardless of other conditions.

I assume that most people are not going to go this route, but it's a valid idea for harm reduction of the expensive bits.