Captscrub

I want to change the diiff fluid in my GT3. I track the car and want to be proactive on maintenance. I have been told to use Mobilube PTX 75w90. When i look it up it is regular trans gear oil. Also any tips on changing the fluid.
Thank you for help. Tried to find past threads about it, to no avail.

Bill Lehman

In a Porsche the differential fluid is the transmission fluid. The fluid recommended will work.

9eight7

I got this tip from @deilenberger. Remove the refill bolt before removing the drain bolt. It's easier to have a drive-able car instead of trying to fill fluid in a hole facing up. I also use a cheap hand pump to pump fluid in. You don't need something fancy here.

Todd B

The transmission/differential is all one unit, same reservoir. I have a motive power fill that I use, makes it super easy to refill a manual transmission.

https://www.motiveproducts.com/colle...th-pinch-clamp

cox1974

Which oil is recommended?
Thanks guys

Todd B

Mobilube PTX 75w90

Captscrub

This PTX is for a PDK car correct. And I can just drain the diff and refill by removing plugs. No need for the Porsche tester

Todd B

yes that is correct for the PDK and that's also for the manual transmission.

PDK wet clutches use automatic transmission fluid.

https://www.suncoastparts.com/produc...iABEgIu1PD_BwE

Kitc2246

I believe all models with a diff cooler are to be run in gear for two minutes then recheck the fluid level to make sure the cooler is full of fluid.

991carreradriver

I had my PDK fluid changed by a Porsche dealer in November the cost was around $600 and if I remember correctly the fluid was about $250. I figured if anything goes wrong I wanted a PCar dealer invested. The price differential wasn't worth it to me.

Stealth 993

I just did this...
Diff/Trans are same unit, there is one fill and 2 drain plugs.

I used Motul 8100 75-90 fluid, the car feels a little smoother, but also did the oil at the same time with Motul 8100.
On my 16 GT3, there was no fill plug, where the fill is there was a seal plug. Right next to it is a oil cooler fitting like 24mm aluminum through nut, that is where I filled mine.
There is not a lot of room for the bolt to go in and out, also getting a wrench in there.

Fluid came out pretty clean, and with only a little bit of smell. I think every 3 years is a good benchmark on changing it.

Todd B

Here's a good thread on the 991 forum. The PDK clutches use the AFT fluid, the transmission/diff are like the manual and use the 75w90 gear oil.

https://rennlist.com/forums/991/1135...id-change.html