996 GT3 Cup Diff Transmission Oil

[PRO 5T]

Any recommendations?

I've been told to run 75W-90 in mine, it's really only done a few hundred miles since it's last full service in 2022 so I figured while I'm changing fluids I'd do the transmission as well.

I can get Millers in the above flavour but I read in some internet posts that we shouldn't be using LS additive transmission oils with cars using a Cup or plated diff, especially if using on track.

I've got a €7k invoice from Manthey for the gearbox rebuild but it only states Motorsport oil when ran through translation!

[mollytherocker]

I believe my 996.2 GT3 has a cup diff fitted too so am interested in the responses!

[PRO 5T]

I think the standard answer is Mobil PTX 75w-90, which is exactly what PARR told me this morning they’ll have put in it at the last service.

Problem is it looks like most places only have that in workshops in big drums, not in 5L tins that we’d need.

[Slippydiff]

PRO 5T said:

I think the standard answer is Mobil PTX 75w-90, which is exactly what PARR told me this morning they’ll have put in it at the last service.

Problem is it looks like most places only have that in workshops in big drums, not in 5L tins that we’d need.

Correct. I'd suggest speaking to Mike at Sports and Classic, I may be wrong, but I seem to recall he was prepared to decant it into smaller quantities.

[Yellow491]

Speak to millers,they will advise.
I use sikolene/fuchs which is very good in some cars and the 993gt2r which has the same diff,motul which is the best,speak to opie oils for these.
The oil will last along time now that motorsport plates have progressed over the years,the oil used to go black as in 993 lsd diffs years ago.

[s_mcneil]

I'm also looking at this and from research on Rennlist, and here, it looks like PTX if you have standard GT3 LSD, SHC (Delvac in USA) if you have cup/motorsport built LSD. I've just bought the SHC from Opie as this looks to be what is currently in mine (cup diff).

[PRO 5T]

s_mcneil said:

I'm also looking at this and from research on Rennlist, and here, it looks like PTX if you have standard GT3 LSD, SHC (Delvac in USA) if you have cup/motorsport built LSD. I've just bought the SHC from Opie as this looks to be what is currently in mine (cup diff).

Good info! How many litres are we expected to use? on a gearbox drain and re-fill?

[Cheburator mk2]

MOTUL 75W90 LS - had Mobil before - too much chatter from the cup plates. Changed to MOTUL - smooth as butter, cheap enough that it gets changed every two years regardless of the mileage...

[s_mcneil]

PRO 5T said:

Good info! How many litres are we expected to use? on a gearbox drain and re-fill?

According to the 997 Workshop manuals between 2.5 and 3.3 litres, my old service invoice has 3.5L listed, I bought 4L.

997.1




997.2