A THUD THUD noise... please help!

[Chuck A.]

Hi everyone,

I finally received my '65 396 Roadster... shipping to South Texas was a real problem this time... over a month! Anyway, I finally drove the car and everything seemed great except... when I was stopped and then strated to turn right or left, I heard a THUD THUD and then the noise stopped when I got straight. This happened everytime. Of course, this happened tonight and it was too late to call a mechanic! I am thinking either a U-joint, the rear end (although it's a posi unit) or maybe even a loose knockoff wheel. These are repros as the car came with steel wheels and hubs which are safely stored.

Any thoughts will be most appreciated.

Thanks,
Chuck A

[Joe L.]

Re: A THUD THUD noise... please help!

Hi everyone,

I finally received my '65 396 Roadster... shipping to South Texas was a real problem this time... over a month! Anyway, I finally drove the car and everything seemed great except... when I was stopped and then strated to turn right or left, I heard a THUD THUD and then the noise stopped when I got straight. This happened everytime. Of course, this happened tonight and it was too late to call a mechanic! I am thinking either a U-joint, the rear end (although it's a posi unit) or maybe even a loose knockoff wheel. These are repros as the car came with steel wheels and hubs which are safely stored.

Any thoughts will be most appreciated.

Thanks,
Chuck A

Chuck-----


Most likely, you've identified the probable sources for the problem. The wheels should be easy to check.

From there, I'd inspect all aspects of the rear suspension with the car on a lift. There might be an obvious problem.

Next, I'd check the u-joints and the differential. The fact that it's a posi doesn't reduce the chance there's a problem with the rear end, it increases it.

[Jim T.]

Re: A THUD THUD noise... please help!

Chuck I recommend that you change the rear end lubricant. If you do it at home you will need a suction gun. GM's rear end lubricant #1052271 SAE 80W-90 if it is still available is what I have always used. Very important to add the Limited Slip Differential Lubricant Additive #1052358, it comes in a 4 oz. bottle. Buying a used car, it is really not known what has been put in your car's rear end.
I had a similiar occurance with my original owner 1968 several years ago and I changed the fluid to correct the problem.

[Chuck A.]

Re: A THUD THUD noise... please help!

Thank you Joe. I will keep everyone posted. Thanks again for your thoughts.

Chuck A

[Chuck A.]

Re: A THUD THUD noise... please help!

Great idea Jim... thanks very much.

Chuck A

[Clem Z.]

Re: A THUD THUD noise... please help!

after you change out the posi lube find a large empty parking lot and do slow figure"8" to get the new lube into all the plates. i have found nothing better for posi than amsoil gear lube.

[Paul J.]

Re: A THUD THUD noise... please help!

Chuck, change the differential lube, as others have suggested. If that doesn't stop it, the differential has to come out.

Paul

[Chuck A.]

Re: A THUD THUD noise... please help!

Thanks Clem. I will do exacrtly what you describe tomorrow after the rear end fluid is drained and replaced.

Thanks,
Chuck A

[Chuck A.]

Re: A THUD THUD noise... please help!

Thanks Paul... of course, I am really hoping its not that bad! Will keep everyone posted.

Thanks,
Chuck A