BFry

I am getting a clunking sound from the rear of the car when it warms up. Also, when it "clunks" it feels like the rear "breaks loose" for a second. Someone mentioned that it may be a problem with the clutches in the positraction. Any way to verify that and will it do much further damage if I can't get it fixed right away? By the way, it is a '68 four speed.

ram82fire

Go to your local gm dealer and purchase some positraction additive and put it in your rear . Go to a local parking lot or suitable space and drive the car in a figure 8 pattern for a few minutes to distribute the additive . If there is no improvement then its time to do some maintenance !

geo

carnut114

Did you try to put new gm gear lube and posi additive? Mine was doing what you are describing until i put the new gm lube in. Now it is totall quiet.
Eric

BFry

I did put in the new lube and the problem is still there. It is not making any other whining noises. I just stopped by my local Chevy dealer and they seemed to think that it might be a transmission problem.

GTR1999

Don't think it's in the Muncie,otherwise you'd get it all the time.
Check the differential front bushing for wear,cracking,slop. Look at the 1/2 shaft joints for rust and movement.

What makes you think it's a posi problem? I have removed posi clutches that were broken and the unit functioned fine. Did you use hte GM additive or another brand? If you didn't use the GM try that. Posi clutch chatter happens when they are hot and you're turning a corner. You may very well have to open the differential to take a look if everything else looks ok.You have to drop the differential out to open it up.

Gary

BFry

Thanks for the input. I will check those areas tomorrow. I'm not sure what additive was used, I had a local vette shop do it while they were doing some other work for me.