I have a 1968 el camino with a 1969 SS Chevelle 12 bolt rear-end in it. About 3 years ago I had the rear end completely overhauled. It has 3:42 strange gears and a eaton posi. Ok this is my problem. From a dead stop when I accelerate lightly and make a turn (left or right) the I feel a some kinda grinding in the rear end. I thought maybe this could also be u-joints but wasn't sure. If the clutch plates are bad in my eaton posi, are they easy to replace or do I need to take it to a mechanic? I'd appreciate any help on this one. Thanks....

There's nothing wrong with your rear end.

Add a bottle of GM "limited slip additive".

RB69 is right just add the posi-trac additive. About 25 years they stopped using whale oil in their rear end grease and have had problems ever since. You could also go to a synthetic lube which should solve the problem.

ok I'll have to try that. where can I locate this oil additive?


Originally posted by Harold Sutton:
RB69 is right just add the posi-trac additive. About 25 years they stopped using whale oil in their rear end grease and have had problems ever since. You could also go to a synthetic lube which should solve the problem.

The dealership sells it and some gear lubes come with it now.

ok I can go to my local Chevy dealer to get it. Is there a name for this oil?


Originally posted by Dragn70:
The dealership sells it and some gear lubes come with it now.

been there it is the opening and closing of the clutch packs. Add gm lube and drive it around in a parking lot doing lefts and rights and circles to lube it up. If it continues add more. I had to add a bunch a year ago and finally it quit.

Ok going to get the GM additive oil this weekend. Also going to drain out the old oil. What does everyone here on the board recommmend for fresh rear end oil?


Originally posted by faulkkev:
been there it is the opening and closing of the clutch packs. Add gm lube and drive it around in a parking lot doing lefts and rights and circles to lube it up. If it continues add more. I had to add a bunch a year ago and finally it quit.

anyone know recommended rear end weight of oil?

If you really want the ultimate in gear oil I'd run 80-140W synthetic and the GM additive.

ok thanks, going to Autozone tomorrow I'll look for it there.

Originally posted by dennis68:
If you really want the ultimate in gear oil I'd run 80-140W synthetic and the GM additive.