Tesla Large Drive Unit (LDU) Motor Teardown and maintenance

[asavage]

The rotor bearing at the gearbox end has a groove nut. It's the equivalent of SKF KM 7.

SKF (and others) KM 7 axial nut ("groove nut")

(https://smile.amazon.com/Whittet-Higgin ... B01EMOZQNU)

(https://youtu.be/_GigD0s47RI?t=129)



While R&R of this nut doesn't necessarily require the mating tool (workarounds exist, including a nice SKF Hook Spanner wrench), the SKF TMFS 7 socket is a "correct" tool, and allows torquing the nut to a specified value if desired. I ordered one from Acorn Industrial (UK) for USD$88 + shipping (USD$112 shipped to my doorstep, six days delivery via DHL).

SKF KM 7 Axial Nut Tool

SKF KM 7 Axial Nut Tool

SKF KM 7 Axial Nut Tool

[WimV]

In attachment some pictures of my triple lip rev Q seal with a small leak for at least 8 months. The seal is 5 years old and 77.000 km.
All the seals are flat without concentric rings or other features. The seal at coolant side and dust lip were in pretty good shape. The middle seal was almost completely gone. There was a black sticky crust of dust between the two coolant lips, this was probably the disintegrated PTFE from the middle lip.
My rotor shaft surface was in pretty bad shape.

[WimV]

By the way: I’ve checked the speed sensor after driving 400 km with the new seal (Ceimin CTLBDYW). Well, that wasn’t what I hoped. There was condensation on the sensor. The drain was still dry (was plugged, so I would know how much it leaked). I collected about one drop of coolant when using some compressed air to flush the reluctor chamber.

I don’t think the speedi sleeves are usable with PTFE seals. I think the seal is stretched too much cause of the increase in diameter.

I’m going to keep driving for a while and keep checking the leak. If it get worse, I’ll pull the rotor to get it welded and grinded to the correct diameter and try with a new seal.

[howardc64]

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[smathermather]

Hi All, this is quite the thread and breakdown on the LDU.

I'm recent 2017 MB bclass owner (b250e), and would you know it: it failed in the way one might predict, 3 or so weeks into owning it. Fortunately, while the seller isn't my favorite car vendor these days, they did provide an extended warranty under a fantastic provider who surprisingly paid for a replacement motor rather than totaling out the vehicle.

The reason I write is, well first to say "Hi" and thank you all for the amount I've already learned on the forum, and second: they aren't putting the original motor type in as it is no longer available (probably all the failures...). Instead they are putting in a "redesigned" motor, which also requires new programming which we are waiting on from MB HQ. Now, I don't know what this means yet, whether this is just an LDU with a better seal or some other motor design, but as I find out more, I'm happy to report on what I can. If it is a redesign of the existing motor it could be interesting to this discussion.

[howardc64]

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[Boxster EV]

Data point and update: after 3500 miles my SKF seal is leaking and progressively getting worse (I have a drain plug so it's dumping coolant overboard). I can see the expansion tank level dropping every few hundred miles and am having to keep it topped up.

I'm not going to have time to remove and examine it before Christmas, but I thought I'd post an update before someone follows my lead with the SKF route (IE don't). I'll take pictures once out of the car.

As a reminder, the SKF seal I used is actually designed for oil applications so it was a long shot expecting it to last any reasonable length of time.

Looks like I'll have to get my rotor shaft repaired and refinished (so that I wont need a speedi sleeve), however we're all still stuck on finding a decent replacement seal.

Edit 20th Jan 2023: After 5000 miles I am actually still running on the SKF seal. It seems that the seal only leaks (at present) when the car is run at higher RPM. I suspect the heat makes the seal surface more supple and the coolant pressure is able to push past it.

I have now fitted the aforementioned SKF seal. It will run on the Speedi sleeve.

I took the car for a blast last night and everything seems fine.

I’ll update any relevant long term feedback in this thread.


Johan kindly did some calculations ref RPM and seal tolerances. With my wheel sizes, the seal will be in tolerance to aprox 12500 RPM which equates to 100MPH.

[muehlpower]

I could also imagine a ceramic flat seal. https://www.kramp.com/shop-be/de/p/mech ... MS114030KR

Of course, this is too long in this design, but it should work with disc springs and/or a reworked housing. The speed would fit (20m/sec)

[howardc64]

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[Boxster EV]

Thanks for posting this information, Howard. The community must find a solution otherwise there will be a lot of LDU off the road in the near future.

I cant find a local link to the snowmobile PTFE lined water seal in the UK. Do you have further information on European suppliers? It only takes me an hour or so to change out the seal and would be willing to give it a try (on the speedi sleeve).

Additionally, do you have a view on whether Nitrile rubber will be more durable than fluoro rubber? The HMS5 S seal I am running is the latter and I'm wondering whether a nitrile equivalent is worth a try?!

[Johan]

Additionally, do you have a view on whether Nitrile rubber will be more durable than fluoro rubber?

Nitrile is worse than fluororubber. See also the graph on page 6 of this thread.

[howardc64]

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[smathermather]

I have confirmed that Mercedes-Benz is using a newer configuration of the Tesla LDUs in their replacements for 2017 and earlier B250e. This is the part:
https://web.archive.org/web/20221205200 ... 2340420184

And here is the part number: 242-340-42-01-84

I don't know much about it yet, but it is what will go into my bclass. Maybe MB has run down the need for a better seal and "solved" the problem. If so, finding out what they use for their seal might be useful, although I am unclear how one would find that info.

[crasbe]

I have confirmed that Mercedes-Benz is using a newer configuration of the Tesla LDUs in their replacements for 2017 and earlier B250e. This is the part:
https://mbparts.mbusa.com/oem-parts/mer ... 2340420184

And here is the part number for when that link inevitably dies some day: 242-340-42-01-84

The Web Archive has you covered: https://web.archive.org/web/20221205200 ... 2340420184

[howardc64]

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[howardc64]

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