I'm posting this question here since I suspect it might be my rearend (my car's rearend). I have a '67 Special (daily driver with 400k miles) with a '68 Chev. open rearend (my original one died and this one was free 12 years ago). I don't know how many miles the rear had originally, but I put an additional 150k+ on it. The problem is whenever I start out from a stop (rarely cold but always when hot) there is a loud CLUNK and it seems to originate from the back of my car. I wasn't sure what was causing the clunking but for other reasons I have replaced the engine with new engine mounts, got a new tranny mount (had the tranny rebuilt), had the driveline professionally rebalanced with new U-joints and made sure that where the tranny crossmember mounts to the frame has good rubber and is tight. The clunking has not changed at all during this whole process and is getting steadily worse. If I stand on the brakes and torque the engine there is no clunking, but 100% of the time if I start from a stop it clunks loud enough for others to hear outside the car. The rear shocks are new and tight and the coils are 12 years old with good rubber insulators. So I'm suspecting either one of the control arm mounts, axle bearings or the diff. itself. Need advice please. Thank you.
Disconnect the d-shaft and see if you can feel it when you rotate the pinion by hand. If not, remove the pumpkin cover and look for metal in the gear oil and/or wear marks. I bet your pinion bearing and/or carrier bearings are worn out. Time for a rebuild. While you have the rear out, install 8 new rear bushings.
