Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

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Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

There’s not a huge amount of detail online about this process so I thought I’d document my recent findings and a suggest a bit of preventative maintenance.

From what I’ve learned, all LDU models can suffer with ‘premature’ motor rotor bearing and pinion bearing failure on mid to higher mileage cars. However, more serious, is a failure of the coolant tube seal which is located on the encoder end of the motor – this fault is common in drive units prior to the ‘Q’ part number revision – however Q model numbers are also affected as seen in this case.

If you’re lucky, bearing failure will just be noisy and can be referred to as ‘milling’ – get it early and it’s no big deal. A coolant tube seal failure is another story altogether and can be catastrophic to three areas of the LDU:


1) If the coolant mixture is not right, rust can form on the surface area where the Teflon seal sits around the rotor tube and will eventually grind a groove on the steel surface (see picture with yellow arrow). If this isn’t identified early enough the rotor / motor could be rendered scrap..

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2) Coolant can get inside the motor assembly and work its way through to the power electronics. In my example I could see a trail of red coolant travelling all the way along the phase legs and into the inverter cover (the bottom of the inverter PCB showed water marks too).

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3) Leaked coolant can cause corrosion of the bearings which may then leave rusty deposits to work into the spline coupler wearing it away, again, rendering the rotor / motor useless. Look closely at the bearing in this picture.... :arrow:

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This particular motor is a spare, but I believe it was run by the previous owner with the incorrect mixture of coolant, with little to no corrosion control. It’s badly rusted inside the rotor tube which has accelerated the seal failure (rusty deposits rubbing the seal contact area as the motor spins). It’s gouged a substantial groove of about 0.25mm deep.

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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

Motor teardown is quite simple:

Remove the coolant pipe and then the motor endplate. The encoder wheel can be pulled off with the motor end plate.

IMG_3751.jpg
The following method is a little alternative, but in order to remove the rotor, I turned the drive unit on its end (motor bottom and inverter top) and placed two blocks of wood under it, at 12 and 6 o’clock, leaving sufficient space between them for the rotor/tube to fall into (make sure you place something soft between the wood to cushion the fall). I then lifted the whole assembly by about 10mm (be careful it’s heavy), and dropped it. The rotor safely detaches from the coupler / bearing housing and drops right out. The bearings could then be removed with a standard puller.
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Once the rotor is out (or before) you can then open the gearbox and start tearing that down -make sure you unplug the motor temp sensor from the logic board and pull the wire through the inverter housing to give yourself some slack. The only point to mention is that the spline coupler will need to be tapped out from inside the motor housing. I used a large socket, extension bar and a few light taps worked.

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Here’s the bearing part numbers (ceramic hybrid):
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Here’s the new seal. I wont provide the part number for this until I've a chance to test it (it's not OEM)
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This is the damage caused by the contaminated seal. I’m going to get this surface turned down between centres and polished, then see how the seals fits, potentially fitting a slightly smaller seal. This is only a test motor so it’ll be an interesting experiment.

IMG_3856.jpg
New drive shaft output seals fitted. These can be bought from ZeroEV:
IMG_3896.jpg
From a preventative maintenance perspective, I’d encourage removing the motor encoder periodically to double check that there’s no moisture inside the encoder wheel area. If it’s wet in there, pull your drive unit and replace that seal!

The various drive unit revisions include improvements to several areas (shims to diff, busbars, phase leg screws, seals, application of gasket sealant, inverter driver boards to name a few). Regardless of what revision LDU you have, unless you know the history and mileage, I’d recommend you do a full rebuild prior to fitting to your car. It’ll save you a lot of aggravation further down the track.

I intend to install this LDU in my Boxster and test it long term with G48 ready mixed anti-freeze. Gearbox oil should be Dexron 6. I’ll then refurb the one that’s currently in the car.
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by muehlpower »

I use SKF Speedi-Sleeve 99114 to repair the surface
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

muehlpower wrote: Fri Feb 04, 2022 8:54 pm I use SKF Speedi-Sleeve 99114 to repair the surface
Wow. That seems like a great solution. Does the surface need to be machined before fitting?
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by muehlpower »

Boxster EV wrote: Fri Feb 04, 2022 10:08 pm
muehlpower wrote: Fri Feb 04, 2022 8:54 pm I use SKF Speedi-Sleeve 99114 to repair the surface
Wow. That seems like a great solution. Does the surface need to be machined before fitting?
No
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by WimV »

Thanks for the pictures! I've noticed some condensation on the encoder in my 2013 Model S (revision Q drive unit), so I'm going to rebuild my drive unit soon. It sounds and drives fine, so I hope there's not too much damage.

What's your experience with the seal you've used? I would like to order the needed parts before I pull the DU...
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

WimV wrote: Sat Mar 12, 2022 10:28 pm Thanks for the pictures! I've noticed some condensation on the encoder in my 2013 Model S (revision Q drive unit), so I'm going to rebuild my drive unit soon. It sounds and drives fine, so I hope there's not too much damage.

What's your experience with the seal you've used? I would like to order the needed parts before I pull the DU...
This is the part from AliExpress. I’ve only put few hundreds miles on the drive unit so too early to tell regarding reliability. I’ll remove the encoder to check once I’ve done 1000 ish miles.
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by WimV »

Thanks! There are 4 different versions:
30x55x8 CTLBDBK
30x55x8 CTLBDYW
36x37x8 CTLBDBK
36x67x8 UH5322-E

Am I correct that 30x55x8 is the water rotor seal and 36x67x8 is the oil seal between rotor and gearbox? Any idea what the difference between both types for each dimension is?

The bearings for the rotor are both 6007-2RZTN9/HC5C3WT I assume? Have you replaced O-rings?

If the rotor looks ok, I don't think I'm going to disassemble the gearbox. It drives perfectly fine without noise (it's a revision Q DU with 70.000 km).

I really appreciate your help! This is my daily driver, so I try to order the needed parts before I disassemble it. :)
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by muehlpower »

I used the BDBK and at least it fit. I don't know what the difference is. I have other sealing rings that are labeled CCWBK. CCW indicates the direction of rotation. Perhaps BD means "both directions", BK = black?
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by WimV »

According to the seller, BK means "oil flooded" and should have a longer life. I don't know what they exactly mean with oil flooded. PTFE often has certain additives to improve friction and dry run, so maybe they mean an additive.
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

So I’ve done 1000 miles in the car with the refurbished drive unit. Yesterday I removed the encoder for inspection and guess what? It’s wet. :cry:
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I’m now going to sleeve it per the above and see how that goes. Although I don’t know whether it’s the pitted surface, or non OEM seal, or both that’s the issue.

A few pictures of the sleeving process - simple to fit but IMO the sleeve could do with being a bit wider. I also drilled a small hole (at the lowest point in the encoder area) to dump inevitable future leaking fluid overboard rather than allowing it into the motor. Need to fit some sort of filter to prevent dust getting in.

I’m still going to see if I can get an OEM seal from Toyota (no chance from Tesla).
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

Hello! I am also repairing a large motor now, I ordered a ceimin 30x55x8 oil seal, do you know if it is possible to find an original or high-quality such oil seal in the USA? Since I'm not in the US
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

Vsevolod wrote: Thu Apr 21, 2022 6:07 pm Hello! I am also repairing a large motor now, I ordered a ceimin 30x55x8 oil seal, do you know if it is possible to find an original or high-quality such oil seal in the USA? Since I'm not in the US
I'm not aware of any OE suppliers of that seal. Please post here if you find one!
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

Boxster EV wrote: Mon May 02, 2022 3:50 pm
Vsevolod wrote: Thu Apr 21, 2022 6:07 pm Hello! I am also repairing a large motor now, I ordered a ceimin 30x55x8 oil seal, do you know if it is possible to find an original or high-quality such oil seal in the USA? Since I'm not in the US
I'm not aware of any OE suppliers of that seal. Please post here if you find one!
Oh sure! If I find something other than Chinese, I will definitely let you know. I have now dried the motor in a vacuum oven (it turned out to be 1.1 gigaohm (1000 mOm) resistance), installed the gland, made a drainage hole with a copper tube (extending), walked with a tap to screw the tube into the thread (I will attach a photo), I’m going to put it in one of these days and see how everything is will, I hope the inverter survived
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Drainage hole and screwed a copper extension tube into it, painted it white
Drainage hole and screwed a copper extension tube into it, painted it white
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

The mod looks interesting.

Will the copper tube connect to the coolant outlet at the bottom? If so, won’t the flow push coolant backwards and back up into the encoder area? Maybe I misunderstood.
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

Boxster EV wrote: Tue May 03, 2022 6:36 pm The mod looks interesting.

Will the copper tube connect to the coolant outlet at the bottom? If so, won’t the flow push coolant backwards and back up into the encoder area? Maybe I misunderstood.
Thanks :) No, the tube will not be connected to the coolant outlet, it has an open end to drain the coolant out (which got into the encoder area), I just made a tube with a thin hole and an angle to make it harder for dirt and water from the street to get in inside the encoder area. How is your motor by the way after a wet sensor? Did the liquid get further, maybe the stuffing box bit during installation?
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by EV_Builder »

Maybe it's an idea to add an one way valve etc. thingy. Petrol tank vents are maybe of use.

Is the water loss big enough to notice it in the bottle?
I would fear apart from the water damage also the lubricant contamination.
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

EV_Builder wrote: Wed May 04, 2022 9:52 am Maybe it's an idea to add an one way valve etc. thingy. Petrol tank vents are maybe of use.

Is the water loss big enough to notice it in the bottle?
I would fear apart from the water damage also the lubricant contamination.
I thought about adding a valve to the drain hole or to my tube, which would allow liquid to come out from the inside, but would not allow any dirt and water to get inside the hole from the street
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

EV_Builder wrote: Wed May 04, 2022 9:52 am Maybe it's an idea to add an one way valve etc. thingy. Petrol tank vents are maybe of use.

Is the water loss big enough to notice it in the bottle?
I would fear apart from the water damage also the lubricant contamination.
In general, the volume of coolant should decrease when the oil seal leaks, but then you need to draw a line with a marker so that even the slightest decrease can be seen, because if a lot of liquid gets in and for a long time, then repairs are more difficult
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by SuperV8 »

Boxster EV wrote: Mon May 02, 2022 3:50 pm
Vsevolod wrote: Thu Apr 21, 2022 6:07 pm Hello! I am also repairing a large motor now, I ordered a ceimin 30x55x8 oil seal, do you know if it is possible to find an original or high-quality such oil seal in the USA? Since I'm not in the US
I'm not aware of any OE suppliers of that seal. Please post here if you find one!
The Merc B250E uses a Tesla motor, and there are seal's available which you should be able to order/by from any Merc dealer.

I can let you know the part number for each from the drawing below - let me know if any look close? Looks like they are £3-£10 so not expensive.

ImageB Class 246 B250E motor
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

Thanks, but the rotor seal doesn’t seem to be illustrated on that drawing? I suspect they consider it an integrated part.

This is the seal in question (it includes the metal outer):
A7DB8B22-E2CE-4EC0-A0CE-409D3F9055A8.jpeg
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by SuperV8 »

Boxster EV wrote: Fri May 06, 2022 10:10 am Thanks, but the rotor seal doesn’t seem to be illustrated on that drawing? I suspect they consider it an integrated part.

This is the seal in question (it includes the metal outer):

A7DB8B22-E2CE-4EC0-A0CE-409D3F9055A8.jpeg
Is that number 56 in the image?

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Quite a difference in price! Can't find any pics to see if it comes with the seal.
Coolant leaking seems quite common in the Tesla B250E and Rav4 EV motors:

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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Boxster EV »

I could be wrong but I think 56 is the coolant outlet seal.
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

SuperV8 wrote: Fri May 06, 2022 9:59 am
Boxster EV wrote: Mon May 02, 2022 3:50 pm
Vsevolod wrote: Thu Apr 21, 2022 6:07 pm Hello! I am also repairing a large motor now, I ordered a ceimin 30x55x8 oil seal, do you know if it is possible to find an original or high-quality such oil seal in the USA? Since I'm not in the US
I'm not aware of any OE suppliers of that seal. Please post here if you find one!
The Merc B250E uses a Tesla motor, and there are seal's available which you should be able to order/by from any Merc dealer.

I can let you know the part number for each from the drawing below - let me know if any look close? Looks like they are £3-£10 so not expensive.

ImageB Class 246 B250E motor
Maybe 40 and 42 to see? Item 40 is similar to where the tube is in the Boxster EV photo
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Re: Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

Post by Vsevolod »

Boxster EV wrote: Fri May 06, 2022 3:49 pm I could be wrong but I think 56 is the coolant outlet seal.
Probably it is. In general, other oil seals have numbers (when parsing the engine), and the rotor oil seal does not have any inscriptions at all. That is the problem
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