80-140 Oil?
Thread Starter
Staging Lane
Joined: May 2004
Posts: 85
Likes: 0
From: County Down, N Ireland
80-140 Oil? I have a stock 98 TA auto with auburn diff (I think). I have read a few times to go for 80-140 oil to quieten down the rear end. Anyone got any advice on this? I thought you were meant to use synthetic oil. It's been noisy since I got it and I had the diff taken apart and new diff carrier bearings installed along with synthetic oil and additive. It was quieter for a while but now the rear creaks and groans and make cracking/clicking noises on tight slow turns. It almost seems as if the gears are jumping the teeth but there didn't seem to be any damage to the diff gears when it was apart. In reverse it seems to be worse and sounds really horrible. Will this 80-140 oil help? 
Before you change the oil, I'd add a tube of GM friction modifier. Clutch-type positraction units need this additive to function smoothly, and without it they make ugly noises while turning (one wheel spinning slower than the other).
