DIY Tesla Drive Unit Repair

[jatguy]

Hi folks, I've just stumbled upon this thread looking for a good solution to repair my LDU. And I'm thinking of creating a pair of parts to replace the rotor cooling tube - similar to QC Charge mod, which I find a bit complicated from the fabrication point of view.
I explain it on the photo of @OhMYLRdy!

The bottom inlet (2) could be replaced with a simple part guiding the coolant directly to the inner stator loop. On the bottom a simple push-in hose connector could be added, to connect parts (1) and (2) in between with short a PVC hose.

The top cover (1) could be just a cap of specific form covering the rotor axle, with a simple internal coolant guide from the push-in hose to a metal cooling tube (1002731-00-A).

What do you think about this idea? I could make CADs for such solution and believe it could be easily CNC-machined for 100-150$ since parts are quite simple.

Could there be any potential issues running the rotor without a coolant at all?

 

[blodg1]

Could there be any potential issues running the rotor without a coolant at all?

Tesla doesn't see a problem with rotor coolant delete.

 

[howardc64]

Hi folks, I've just stumbled upon this thread looking for a good solution to repair my LDU. And I'm thinking of creating a pair of parts to replace the rotor cooling tube - similar to QC Charge mod, which I find a bit complicated from the fabrication point of view.
I explain it on the photo of @OhMYLRdy!

The bottom inlet (2) could be replaced with a simple part guiding the coolant directly to the inner stator loop. On the bottom a simple push-in hose connector could be added, to connect parts (1) and (2) in between with short a PVC hose.

The top cover (1) could be just a cap of specific form covering the rotor axle, with a simple internal coolant guide from the push-in hose to a metal cooling tube (1002731-00-A).

What do you think about this idea? I could make CADs for such solution and believe it could be easily CNC-machined for 100-150$ since parts are quite simple.

Could there be any potential issues running the rotor without a coolant at all?

I had similar ideas. Post #139 shows analysis of eliminating coolant channel through the fly over tube. I guess main purpose of that channel is just so rotor coolant channel have a return line. Not sure if much benefit for air bleed.

However, if willing to do simple dremel modification of existing manifold : Cut off rotor tube on existing manifold, remove circlip, and grind down rotor tube to the shoulder below the circlip (2nd pic in post #189), then a simple cap (different cap idea than yours) can be made to seal the existing seal bore AND still provide coolant flowing channel to exit top of the manifold. It's not as easy as a bolt on replacement part but should be able to modify by dremel (most people have) without too much time.

For cap dimensions, look at post #197 pic and #198 PDF file (page 1). If cap dimension is correct, then just press in. Rotor cooling is deleted and coolant still through the fly over tube.

• 55mm dia @ 8-10mm deep, maybe don't go all the way to 10mm and leave a small gap for RTV to collect after pushing in the cap
• then a smaller diameter extension since manifold diameter is smaller after 55mmm seal bore and still need to go deeper due to protruding rotor shaft.
• cup needs total of ~15mm depth from top of seal bore to clear the rotor shaft. Still have 4mm remaining, then coolant will still flow through the manifold. Not go to the rotor (capped) and exit off top into the fly over tube.

If cap is made out of Al, I don't have experience glue/press/RTV into existing Al bore. For stainless steel, I measured Ceimin triple lip seal's ( post #57 has seal pic ) stainless steel cage. They size it average 5-15/1000th mm above 55mm for interference fit. Stainless steel compress easier than Al for interference fit of course.

 

[howardc64]

BTW, @blodg1 solution for drilling + sleeve a tube for coolant delete (post #108 also know others that have done 10+ same way) works because there is at least 5mm+ of clearance from shoulder below circlip to the rotor shaft per my measurements in post #198. Quite a bit of space although everything is within just a couple of mm(s) so difficult to judge by eye alone.

But I guess I'm still too chicken to drill the sleeve tube so keep on thinking about the cap solution in post #197 #198

 

[mr_hyde]

BTW, @blodg1 solution for drilling + sleeve a tube for coolant delete (post #108 also know others that have done 10+ same way) works because there is at least 5mm+ of clearance from shoulder below circlip to the rotor shaft per my measurements in post #198. Quite a bit of space although everything is within just a couple of mm(s) so difficult to judge by eye alone.

But I guess I'm still too chicken to drill the sleeve tube so keep on thinking about the cap solution in post #197 #198

If someone can source a two-stage cap to press into the seal bore, it would be the simplest (cost effective) solution by far. I would caution people to make sure there is no coolant inside the motor already before doing just the manifold. Once the coolant is there, it will rust and cause other unpleasant issues and it won't evaporate. You don't want to do all this work and have bearings howling in 5k miles. Make sure it is dry...

 

[brainhouston]

I ordered some aluminum stock n will be milling one soon

 

[howardc64]

If someone can source a two-stage cap to press into the seal bore, it would be the simplest (cost effective) solution by far. I would caution people to make sure there is no coolant inside the motor already before doing just the manifold. Once the coolant is there, it will rust and cause other unpleasant issues and it won't evaporate. You don't want to do all this work and have bearings howling in 5k miles. Make sure it is dry...

To add context for others

@mr_hyde came over and helped me pull the reluctor wheel, speedi-sleeve, and the rotor. My < 1k miles test of an SKF FKM seal that failed (should fail by design due to low surface speed but a couple of people said been running dry for thousands of miles) Failure resulted in coolant near bore of both rotor bearings. If not cleaned, will continue to do damage.

Info here if anyone curious on this seal + speedi-sleeve failure.

Tesla Large Drive Unit (LDU) Motor Teardown and maintenance - Page 19 - openinverter forum

 

[jatguy]

I could make CADs for such solution and believe it could be easily CNC-machined for 100-150$ since parts are quite simple.

So, I did a preliminary design of the parts. The idea is to completely replace the rotor cooling tube (1006606-10-B) with a pair of parts. The lower part is basically just a feedthrough to the stator and the bottom 8mm hose connector. The upper part has the the vertical channel to feed the coolant to the upper metal cooling tube (1002731-00-A).

Since parts are very simple they can be done on even on a 2-axis CNC or a milling machine, with a single cutting tool + drilling and threading.
I assume the manufacturing cost <100$ for both.

Any comments on such design? I am planning to make a prototype next week.

 

[howardc64]

So, I did a preliminary design of the parts. The idea is to completely replace the rotor cooling tube (1006606-10-B) with a pair of parts. The lower part is basically just a feedthrough to the stator and the bottom 8mm hose connector. The upper part has the the vertical channel to feed the coolant to the upper metal cooling tube (1002731-00-A).

Since parts are very simple they can be done on even on a 2-axis CNC or a milling machine, with a single cutting tool + drilling and threading.
I assume the manufacturing cost <100$ for both.

Any comments on such design? I am planning to make a prototype next week.

This may not matter but the coolant inlet in diagram is for MB 250e / Rav4EV. Model S sticks straight out

Tesla Large Drive Unit (LDU) Motor Teardown and maintenance - openinverter forum

TeslaLDU - Parts

Ordering Parts Tesla: Tesla part numbering explained @ TMC. Official: epc.tesla.com (as of 9/2022, not a good way to order parts even for "over the counter" parts shown in the parts catalog. Ordering process goes through Tesla app which may requires a Tesla VIN to register. See also: here and here

sites.google.com

Bottom of LDU where inlet is also not too far from the mid aero shield (just belly pan that covers the LDU+subframe) Don't have mine mounted ATM but maybe 2-3+ inches clearance? Don't recall. Tesla subframe also wraps around pretty close so need to make sure that connection tube between 2 pieces clears everything. A straight in between 2 pieces pipe more ideal but maybe some reason (threaded pipe connector?) steered you towards the diagramed solution. Here are couple of pics in earlier posts

https://teslamotorsclub.com/tmc/attachments/img_2542-1-jpeg.853239/

https://teslamotorsclub.com/tmc/attachments/img_2582-jpeg.853771/

https://teslamotorsclub.com/tmc/attachments/img_2583-jpeg.853772/

https://teslamotorsclub.com/tmc/attachments/img_2546-jpeg.853044/

A post with a couple of more reference pics. Subframe looks like an octopus wrapped around the LDU haha

Tesla Large Drive Unit (LDU) Motor Teardown and maintenance - Page 8 - openinverter forum

I actually remove the inlet prior to pulling the LDU from subframe for clearance / not breaking it haha.

 

[brainhouston]

So, I did a preliminary design of the parts. The idea is to completely replace the rotor cooling tube (1006606-10-B) with a pair of parts. The lower part is basically just a feedthrough to the stator and the bottom 8mm hose connector. The upper part has the the vertical channel to feed the coolant to the upper metal cooling tube (1002731-00-A).

Since parts are very simple they can be done on even on a 2-axis CNC or a milling machine, with a single cutting tool + drilling and threading.
I assume the manufacturing cost <100$ for both.

Any comments on such design? I am planning to make a prototype next week.

i feel like this is over-complicated...
why not go straight to small tube?..

And even more simpler, me n Howard discussed about completely removing top tube n blocking it at gearbox input
Theory is, with rotor cooling, this thin tube would get relatively hot coolant, combined with the fact that gearbox entry is very fine (~5mm) opening, makes it seem like not much cooling was happening there.. So removing that passage shouldn't hurt gearbox since it has other larger route for coolant.

 

[jatguy]

Bottom of LDU where inlet is also not too far from the mid aero shield (just belly pan that covers the LDU+subframe) Don't have mine mounted ATM but maybe 2-3+ inches clearance?

Thanks for the photos, indeed I think the bottom hose connector could be moved to the top.

i feel like this is over-complicated...
why not go straight to small tube?..
And even more simpler, me n Howard discussed about completely removing top tube n blocking it at gearbox input

I would tend to not block the gearbox input completely, since this is too much of a customization from my point of view. I personally don't know 100% what is the function of that coolant loop and would tend to keep it even if it actually useless.

Removing/cutting the cooling tube (1002731-00-A) could make sense, but if I would like to keep the coolant flow to the gearbox - there should be another way of connecting 8mm hose to that metal tube or to the gearbox input itself. And I don't see a reliable solution here:
- in case of cutting the tube - I think clamping the hose on the tube end is not a very reliable type of connection + one would need to destroy a functional part, leaving no way back to the original configuration.
- in case of a complete tube removal one will need to get an extra custom-made "hose-gearbox" connection part with the o-ring (the same as on the original tube) + find the way how to guide and hold the tube until that gearbox input. Also a complicated solution as for me.

 

[brainhouston]

Thanks for the photos, indeed I think the bottom hose connector could be moved to the top.


I would tend to not block the gearbox input completely, since this is too much of a customization from my point of view. I personally don't know 100% what is the function of that coolant loop and would tend to keep it even if it actually useless.

Removing/cutting the cooling tube (1002731-00-A) could make sense, but if I would like to keep the coolant flow to the gearbox - there should be another way of connecting 8mm hose to that metal tube or to the gearbox input itself. And I don't see a reliable solution here:
- in case of cutting the tube - I think clamping the hose on the tube end is not a very reliable type of connection + one would need to destroy a functional part, leaving no way back to the original configuration.
- in case of a complete tube removal one will need to get an extra custom-made "hose-gearbox" connection part with the o-ring (the same as on the original tube) + find the way how to guide and hold the tube until that gearbox input. Also a complicated solution as for me.

makes sense..
i also just realized that running coolant thru manifold (teslas bypass n urs) would at least remove some heat, just from hot air exchange inside, kind of acting like an air heatsink.. so probably good idea to keep it just in case.

 

[blodg1]

So, I did a preliminary design of the parts. The idea is to completely replace the rotor cooling tube (1006606-10-B) with a pair of parts. The lower part is basically just a feedthrough to the stator and the bottom 8mm hose connector. The upper part has the the vertical channel to feed the coolant to the upper metal cooling tube (1002731-00-A).

Since parts are very simple they can be done on even on a 2-axis CNC or a milling machine, with a single cutting tool + drilling and threading.
I assume the manufacturing cost <100$ for both.

Any comments on such design? I am planning to make a prototype next week.

Nice work. I think a one piece design would be simpler. It would also make me more confident that the lower passage would be better sealed when not relying on only two fasteners.

 

[mr_hyde]

makes sense..
i also just realized that running coolant thru manifold (teslas bypass n urs) would at least remove some heat, just from hot air exchange inside, kind of acting like an air heatsink.. so probably good idea to keep it just in case.

I'm thinking about the cooling of the gearbox from the original design and I suspect the coolant exiting the rotor is hotter than the gearbox fluid on the other side of the heat exchanger. I don't think that coolant is doing any 'cooling' in the original design. More likely, it serves to keep a stable thermal profile across the entire LDU assembly. If you run 'cool' coolant there that hasn't be pre-heated by the rotor, it will be cooling the top of the gearbox more than the original design.

 

[brainhouston]

I'm thinking about the cooling of the gearbox from the original design and I suspect the coolant exiting the rotor is hotter than the gearbox fluid on the other side of the heat exchanger. I don't think that coolant is doing any 'cooling' in the original design. More likely, it serves to keep a stable thermal profile across the entire LDU assembly. If you run 'cool' coolant there that hasn't be pre-heated by the rotor, it will be cooling the top of the gearbox more than the original design.

yeah i said same thing in post #210
i personally think that either bypass (with or without top tube) will work just fine, temp differences will most likely be negligible
i'm sure we'll get some confirmations later after many DIY mods over time...

 

[Z3ds]

So I did the coolant delete today. I cut the manifold with a reciprocating saw and capped the bottom part and upper part with JBweld water weld. I used a 3/4 1/2 3/4 tee to supply coolant to the upper tube that goes to the heat exchange. It took me about an hour. I had to top off the reservoir with about a gallon of coolant every now and then. Drove for 10 min so far so good.

 

[howardc64]

An EU member posted on @NV Ray FB group their still under warranty MS's reman rev T LDU leaked and got another reman rev T. This member was wondering if Tesla "reverted" Sport LDU from -U to -T in EU due to thermal problem. EU catalog shows Base LDU is reman Rev-Q and Sport LDU is reman Rev-T. New is unavailable in this catalog.

https://teslacarparts.eu/catalog/motor-large-rear-drive-unit-2368/index.html

Any EU member can confirm if -U was ever present in EU? Been available in US for 3+? months now.

According to the revision info I have been collecting. Rev Q for base and T for Sport was the last LDU revisions we saw in DIY community

Tesla LDU - Revisions

Many Revisions Tesla has had many version of the LDU and most cars were getting LDUs replaces every few 10k miles with regularity. My 2013 MS has had the original (don't know Rev) to Rev K and then onto Rev Q all in 40k miles. There are some differences between all these Revs. Following is not a

sites.google.com

Finally, Tesla can fix all this by just allowing swapping LDU for SDU. I heard a RWD Model S was a test mule during SDU development. If Tesla just enable this configuration in software, then there is probably hope to replace LDU by SDU. No chance as of now.

 

[brainhouston]

Interesting.. might be a supply issue...
I don't see how they would be swapping P motors here with -U but not in EU...

I don't see a reason for SDU..
RWD can run fine without coolant (not much power) and Perf can't use SDU...

 

[rowdy]

Interesting.. might be a supply issue...
I don't see how they would be swapping P motors here with -U but not in EU...

Yep probably just running down the stock they already have. I expect warranty repairs will keep getting T revision remans until they have exhausted their stockpile.

I went through similar in Australia, Tesla only had T reman units available in stock. It was made clear to me that if it was a warranty replacement then this is what I would be getting. However since I was paying in full for the DU they were ok to order in a U revision for me.

 

[howardc64]

Using Air to Cool?

Regarding cooling the rotor, maybe there is another possible option : Forced Air. Just like CPU+GPU in computers can be cooled by 2-3 methods

• Fan + heat sink / fins to increase heat exchanger surface area
• AIr jets (not in consumer computers but I think have been used in the past in big servers) Its basically air flow rate so jets = smaller + higher pressure to gain more air flow / volume area.
• Liquid radiator of course which is similar to LDU.

For air cooling, cool air would need to be pumped down the existing coolant tube inside the rotor. U turn at the end to come out to an exit path.

Seal is probably necessary to avoid forcing air into reluctor wheel chamber and pressure against the bearing. PTFE seal would probably have to be the choice again with surface speed and survive seal lip thermal density.

I don't know the heat removal difference between coolant, oil, and air. Surely coolant is best and flow rate matters as well.

I guess the good thing is any failure in air flow cooling = no worse than no cooling? No water/oil leak into everywhere electricity is present. Assuming forced air doesn't leak past the seal and damage the bearings in someway.

Chrome Plating Shaft Repair

Been in touch with with a Norwegian 2014 MS owner with leaked LDU and scored rotor shaft. Successfully repaired shaft with chrome plating and Ceimin triple lip seal. Left some notes here

Tesla Large Drive Unit (LDU) Motor Teardown and maintenance - Page 19 - openinverter forum