[trimer]

Originally Posted by steved0x

The redline application guide says this car should use their MT-90, which is a GL-4. I think Mobile Delvac is a GL-5. I use the delvac in the diffs for my tacomas (well I sold one so the one that is left ) and in my FJ cruiser. I use the MT90 in the 5 speed in the Tacoma, and also my son's Miata transmission, which hates GL5.

It could very well be the fluid, and there are not many GL4 out there. I think Brad Penn makes one:
http://www.summitracing.com/search/product-line/brad-penn-multipurpose-classic-gl-4-gear-oil

And redline makes a couple of GL4s, the MT90 is the one I use on my vehicles that call for a GL4:
Red Line Synthetic Oil - Gear Oil for Manual Transmissions - MT-90 75W90 GL-4 Gear Oil

Edit: I may be way off, I was putting in 1988 Porsche 944 Turbo into the redline application guide for the above. I just saw in your sig that yours in a 1989, so I put that into the redline application guide and this is what it recommended for the transaxle: 75W90 GL5
Red Line Synthetic Oil - Gear Oil for Manual Transmissions - 75W90 NS GL-5 Gear Oil

Sounds like that is about the same as the Mobile Delvac 75W90. Good luck, hopefully a fluid change will help.

Steve

Thanks Steve. We discussed redline as well. They make one called swepco that a lot of 944 guys use as well. Trial and error, or I rip the whole transmission out and start over, cause you know, I have millions of dollars to spend on a car...why not...lol. Pain in the but. I am missing both my Boxsters right now!