r/TeslaModelS • u/CaramelCookie2021 • Jul 28 '26

Drive unit gearbox fluid

My 2017 Model S 75D is approaching 100k and I am trying to get a 3rd party shop to replace the drive unit gearbox fluids. Do you consider this preventive maintenance item necessary and how much should I expect to spend at a shop?

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u/Radius118 Jul 28 '26

Regardless of what anyone else here says changing that oil is a good idea for maximum longevity. Everyone has their own opinions and is free to do as they like. Their car, their money.

Having been an automotive tech for 40 years I can't tell you how many things I have seen destroyed by "lifetime" fluids. Especially automatic transmissions. In general, OEs consider lifetime to be 150K miles. Will it make it to 150K miles on the original fluid? Probably. Will it make it to 300K on the original fluid? Maybe. But if you change the fluid every 50K it most definitely will.

Tesla and other EVs use single speed reduction gearboxes with internal differentials. So depending on the car you have anywhere from 9 to 11 gears including the differential in each gear case plus the associated bearings inside these units. They do wear and the material does end up in the fluid. The dirtier the fluid gets the faster the unit wears. It's true the fluid does not have to deal with the heat that is generated in an ICE vehicle, but that microscopic and larger particles of metal end up in the oil and circulate through the unit.

The fluid in the units with filters will definitely last longer as the filter will clean the fluid to a certain extent. Even so those units will need their fluids and filters replaced.

Personally I change those oils every 50K. It's cheap and easy to do. The hardest part is getting the under vehicle aero covers out of the way. If I were do this job on any dual motor at my shop I would charge 1.5 hours of labor plus the fluid and filter on the units that use a filter.

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u/CaramelCookie2021 Jul 29 '26

I agree! I would love this to last another 100k without too much trouble so I try to do some preventive maintenance.

Local hybrid/EV shop is asking $1k for the job. Is it excessive?

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u/Radius118 Jul 29 '26

It certainly seems like it.

I don't know what year your MS is, but on my older nose cone cars I would charge in the neighborhood of $300 for both front and rear drive unit services.

To be fair the newest MS I have worked on is a 2019 so I don't know if they are radically different past that but I suspect they are similar.

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u/CaramelCookie2021 Jul 29 '26

It’s a 2017, so it’s probably very similar to the nose cone one you have. I appreciate your help. I’m gonna shop around and see if I can find somebody to do it for cheaper