I'm Getting some thunking from the rear when dropping the auto trans. into gear. I'd like to check the U-joints \ remove the halfshafts if neccessary. Any tips on procedure to inspect and or removal would be greatly appreciated.
Mike

 

check the differential mount first!

 

More-over, check everything first. You should be able to
see the movement that makes the "thunk" ... turning parts by hand.

 

I did my u-joints last year and I'm still getting a thunk - so yours could be either u-joints or diff. I vote diff. But only way to tell for sure is to do what NHvette said.

If it is the u-joints, it is fairly easy to remove the half shafts (getting them back on can be a bit tricky - needed a friend to help me. One person holds the shaft in place while another tightens the bolts). On my '80 there are just 8 bolts. I think I used a 12 point, 5/16 socket. You may additionaly have French tabs on the 78, which will need to be bent open and then replaced with new ones.

You can then either replace the u-joints yourself, or send them out to a shop (search the archives for procedures on changing them yourself). When you put them back on, use some loctite on the threads.

You'll also need to decide whether to use u-joints with or without the zerks. For a daily driver without alot of horsepower, go for the greasable ones with the zerks. The zerk needs to be in a special position, so that its compressed as the wheel turns forward.

But I'm jumping the gun here, it could be the diff!

 

Thanks to all that responded. Looks like its empty the wallet time again..*S

 

A friend of mine had a problem with his 79' a couple of months back and I thought his u-joints needed replaced also, but when he took it in, the shop told him his u-joints were not bad. It turned out the fluid in the differential needed changed. No more problem!

 

i had the same problem and did everything to my rear end and it finally turned out that when i pulled my differential and put it back in i didnt tourque the bolts to what they are suppose to be and i was getting a thumping from the rear.

 

Hey Mike
If the U joints havent been replaced in a long time do yourself a favor and buy some new ones. The amount of time you will spend to check them it is better to replace them. They are not all that expensive. You can do most of the work yourself and save some money. First put the car on a good set of jack stands. Remove both rear wheels. There is a rod that mounts from the bottom of the shock to the center bracket. This rod is the strut rod. It has a bolt on the inboard side or near the differential that is used to adjust the rear alignment. Mark the bolt head in relation to the bracket. Do this to both bolts. The purpose of this is to set the alignment back to the original position, or else you will have to pay for an alignment.

You will want to loosen these adjustment bolts as to it makes it easier to get the half shafts out. These bolts should be 3/4 or 11/16 in size. Next remove the bolts that hold the caps for the u joints inboard and outboard. The half shaft should come out by raising or lowering the trailing arm or another words the wheel assembly. It is easier to take these to a machine shop to have the old u-joints pressed out and new ones pressed in. You will find the passenger side outboard is the worst.

While you have the halfshafts out do yourself a favor and replace the fluid in the rear end. To remove the old fluid get a large turkey baster and put a 12inch length of clear hose on the end. Suck out all the old fluid. Replace the fluid with gear lube from your local gm dealer. You will need 2 bottles of gear lube and two small bottles of additive. Do not use anything else. The additive is specially formulated for the clutches in the rearend. What all this will prevent is a slight clunking noise and a strange but very slight side to side motion by the rear of the car when you are turning towards the right at a very slow speed.
Hope this will be of some help.

 

CHECK REAR SPINDLE BEARINGS OR SEE HOW MUCH WIGGLE YOU GOT ON YOUR TIRE MOVE IT TO THE VERTICAL IF YOU CAN SEE YOUR DRIVE SHAFT MOVING ON THE BACK SIDE OH YA SHOCKS THE REST OF THE BOYS COVERED EVERYTHING ELSE..HOPE IT HELPS.

 

Had the same on my 77, new fluid and additive and the problem went away.

 

Don't know if this will help... but:

I'm having a 700r4 put in. I should get it back 3 weeks ago..... which will hopefully end up being this coming monday Anyhow, among the things that the mech. found in need of repair on my 71 was the right rear half/axle shaft. He said the end was worn and was allowing for some serious play in the diff. He concluded that some of the strange noises i had been hearing, and my problems with keeping the car aligned are probably due to this. Of course, it will be hard to tell what really fixed my car as pretty much the whole drivetrain, transmission back is being replace Hopefully this will help a little!