My 96 Camaro with 3.4 engine and AT just started making a thumping noise when it is decelerating. Seems to be in the power train as the frequency is dependent on speed. I assume that the car still has the 2 piece driveshaft.

It does NOT make the noise when speeding up and seems worse when turning sharply left as compared to not as bad turning right. Don't feel any vibration either in steering, brakes or car at any time. Just the thump. I figure either the U-joints, carrier bearing or tranny mount but am trying to figure out how to eliminate all but one of these. Anybody had this problem and ideas on how to best determine the real issue?

 

Before taking stuff apart, take a good look at your tires. You may have hit a pot hole and damged the cords.

 

Could also be a bad wheel bearing, on the right side. Check that while you're checking the tires.

 

Thanks for the ideas. Will take a look at the tires and bearings but don't think those are giving me this problem. Jacked it up to see for sure that I do have the 2-piece driveshaft. Afterwards, I drove it a short distance and the noise was accompanied by vibration in the car and occurred when I was accelerating or decelerating so I am thinking U-joint is likely, although it could be the carrier bearing. I looked at the trans mount, and it did not appear collapsed or loose.

 

BTW, I realized my OP mentioned that it was a 3.4 engine, actually is a 3.8 engine. I apparently was thinking about my 94 Camaro which DOES have the 3.4 and requires parts more frequently than the 96.

 

The thumping could be the tranny smacking the floor. A bad mount would also cause some vibrations but the u joints would cause alot same with a bad carreir bearing. But if your replacing them do your self a favor and find a 1 peice steal drive shaft from any 3rd or 4th gen and intall that. Your car will have a little more pep to it and you'll loose the weight of that useless carreir bearing.

 

Another thing since it makes this noise when turning left check your spare. Make sure it's not loose.

 

Thanks, will take a look when I get a chance over the holidays. I was already thinking about changing to the 1 piece driveshaft, particularly if carrier bearing seems to be part of the problem. I have never thought much of the 2-piece. Doesn't seem to be from spare tire, and I did think more about the trans mount after thinking about the way it was worse turning one way. Will update when I determine anything.

Merry Christmas, Everyone!

 

Also check to make sure all your lug nuts are good and tight. You will get a thump like that if a wheel is loose.