kbc993

I need to replace trans fluid in 2003 Cup car, Mobil 1 75-140 or 75-90?

LVDell

HERE YOU GO

Geoffrey

Yep, LVDell's recommendation is the correct oil. It is different than the Mobil 1 Synthetic 75/90 found at the local autoparts store. The latter has too many friction modifiers in it and affects the ability of the syncro to grab the gear properly. IE it is too slippery an oil.

kev

Hey Keith, is that you?

Did you and Andy do the Gingerman race, if so how'd it go?

BC

It says its also good for the 915 synchros, which usually need a less slippery oil. Swepco is usually suggested in these cases, but it is not synthetic. If this has the characteristics of a conventional gear oil in its ability go help the Porsche based sychros to work, but also has the synthetic temperature stability and shock resistance, it would be "Super cool"

Phokaioglaukos

Here is a link to my message attaching the data sheets for the oils lots of people use: HERE.

You can see the whole thread HERE

AndyT

is the 75/90 ok for non cup cars ?

Geoffrey

Use the above for all G50 transmissions, race or street.

jaholmes

I have tried the Delvac and the Mobil1 the dealers used recently on my 993 and it just isn't right. Before the change I had the original factory mystery fill and shifting was pretty good. Now shifting sucks and I feel 2nd and 3rd gears all the time now. Is the new fluid showing the wear I have on my synchros. I only have 50k miles.

LVDell

The 2 at the dealer for the 996 are not mystery. They are Mobil Mobillube PTX and Shell Transaxle. Mobillube is rec'd for the GT3 and the Transaxle for all the rest. The Mobillube is VERY pricey and only sold in 20L drums. You either pay the dealer for the change ($$$) or get them to sell you by the liter in a container you provide.

jaholmes

LVDell,
I was referring to the original factory fill in 1997 for my 993. For my recent change, it is my understanding the dealer put Mobil1 in and I hope it's Motolube, I am going to call and find out. I don't think it was shell.

Either way the shifting sucks compared to what it was before. I will know more on Monday at the track.

LVDell

Ah, I didn't even see that. I just glanced over your post. My mistake. It clearly states 993

JasonAndreas

You will have the same problem with Mobil-1 SHC. There was something in the original 964/993 factory fill that was good at masking problems and that is now missing from available gear lubes. I (and quite a few other people) have had nearly (my problems happen only with a cold gearbox) the same issues crop up immediately after a lube change and I have since tried several different brands with very little improvement.

LVDell

We can't get the SHC here in the states. Delvac is the replacment for it. As far as what is good for the 993 that is something I can't comment on. Hopefully somebody can chime in on that.

jaholmes

I read my receipt from the dealer and they put in 80W90 Gear lube. So now I want to know what it is.

JasonAndreas,

I put in the Delvac stuff from Lufetnic...which I thought would work but that is where my problems started. I drained out the original factory fill. So then I went to the dealer to have them put in the Mobil1 they recommend and still the same problems.

I have probably spend $500.00 in transmission oil changes...WTF...I could have bought a midrise lift and been half-way there and do it myself.

I did post this on the 993 board and most responded that they are having the same issues.

So is anything short of a transmission rebuild going to fix this problem. Did the original factory fill mask the wear on the transmission and cause it to wear more.

Any idea what a rebuid would cost considering you can get a new /31 gearbox for $7,500.00.