Transmission Oil
11-13-2002, 10:02 PM
#1
Nordschleife Master
Thread Starter
Transmission Oil
I think I need to change out my Trans fluid for my 87 951 with LSD as the shifting is getting a little stiff in this colder weather. Any recommendations for what type of fluid I need to use in my 5 speed factory LSD gearbox?
11-14-2002, 10:30 AM
#2
Addict
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I'm using Mobil 1 synthetic - seems to work pretty well (80W90, I think).
-Grant
88 951S w/ LSD
-Grant
88 951S w/ LSD
11-15-2002, 03:45 PM
#3
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Dan-
I like Red Line products and use MT-90 in my 951 race car. Attached is a response from Red Line you might find helpful:
I race a Porsche 944 Turbo with a stock 5 speed manual transaxle with factory limited slip. (dedicated race car) I have been running your MT-90 in my transaxle. (2nd season) I have recently been told to consider switching to your 75W90 Gear Oil because it contains "limited slip friction modifiers".
1) Is this a more appropriate lubricant for my application? (75W90 Gear Oil vs. MT-90)
In most 944 Porsche/ Audi type transaxles a GL-4 is called for and I would recommend the MT-90. If the MT-90 is working well, I would keep using it.
2) Does the MT-90 have the same limited slip friction modifiers as the 75W90 Gear Oil? If so, same amount?
The MT-90 contains a little friction modifier, about 10% as much as the 75W90. The friction modifier is typically needed in a rear differential with limited slip used on the street to reduce chatter when making a slow tight turn. In you application this isn't an issue. You won't experience any chatter in a race car because you don't make slow tight turns, the synchros in the gear box need some friction to operate and transaxles typically don't require as much friction modifier. I would not recommend the 75W90 because it will probably be too slippery for the synchros, the added friction modifier can also reduce the lock-up of the limited slip, in track use this generally isn't desired either.
3) I was told by German Transaxle, where I purchased this new transaxle, to run MT-90 because it is a GL-4 gear oil. I was told, in no uncertain terms, to not run a GL-5 rated oil. Is the 75W90 a GL-4 rated oil?
The 75W90 is a GL-5, not a GL-4. Some GL-5 gear lubes can be corrosive to the brass and bronze synchros and bushings, though not the Red Line GL-5s. The other problem with most GL-5s is the amount of friction modifier used make them too slippery for the synchros.
4) I was also told that a GL-5 rated oil may be too slippery for the brass synchros ... is this correct? I roached my previous transaxle (synchros) and was told it most likely was because I was using a GL-5 rated oil.
Yes GL-5 typically are too slippery for the synchros.
The problems could have been due to the fluid being too slippery or corrosion, or both.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
I like Red Line products and use MT-90 in my 951 race car. Attached is a response from Red Line you might find helpful:
I race a Porsche 944 Turbo with a stock 5 speed manual transaxle with factory limited slip. (dedicated race car) I have been running your MT-90 in my transaxle. (2nd season) I have recently been told to consider switching to your 75W90 Gear Oil because it contains "limited slip friction modifiers".
1) Is this a more appropriate lubricant for my application? (75W90 Gear Oil vs. MT-90)
In most 944 Porsche/ Audi type transaxles a GL-4 is called for and I would recommend the MT-90. If the MT-90 is working well, I would keep using it.
2) Does the MT-90 have the same limited slip friction modifiers as the 75W90 Gear Oil? If so, same amount?
The MT-90 contains a little friction modifier, about 10% as much as the 75W90. The friction modifier is typically needed in a rear differential with limited slip used on the street to reduce chatter when making a slow tight turn. In you application this isn't an issue. You won't experience any chatter in a race car because you don't make slow tight turns, the synchros in the gear box need some friction to operate and transaxles typically don't require as much friction modifier. I would not recommend the 75W90 because it will probably be too slippery for the synchros, the added friction modifier can also reduce the lock-up of the limited slip, in track use this generally isn't desired either.
3) I was told by German Transaxle, where I purchased this new transaxle, to run MT-90 because it is a GL-4 gear oil. I was told, in no uncertain terms, to not run a GL-5 rated oil. Is the 75W90 a GL-4 rated oil?
The 75W90 is a GL-5, not a GL-4. Some GL-5 gear lubes can be corrosive to the brass and bronze synchros and bushings, though not the Red Line GL-5s. The other problem with most GL-5s is the amount of friction modifier used make them too slippery for the synchros.
4) I was also told that a GL-5 rated oil may be too slippery for the brass synchros ... is this correct? I roached my previous transaxle (synchros) and was told it most likely was because I was using a GL-5 rated oil.
Yes GL-5 typically are too slippery for the synchros.
The problems could have been due to the fluid being too slippery or corrosion, or both.
<img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" /> <img src="graemlins/burnout.gif" border="0" alt="[burnout]" />
11-15-2002, 05:58 PM
#4
Addict
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Thanks for the great info, Belz! I'm going to go get a gallof of the MT-90 today (heading to the track this weekend and I'm going to remove the Mobil 1 - GL5 according to their website)
