When I would jack up the car with the rear wheels off the ground, there was always a bind in the rear end. I could spin one of the rear wheels part way around and it would hit a tight spot. I assumed it was the posi unit. When driving I didn't notice anything

I just replaced the pinion seal and driveshaft U-joints. After getting it all back together, I back it up a few feet and it seems like the bind is stopping the car. I roll it forward past where it was originally, all is smooth. I back it up a few feet and it seems OK. I back it to the street and go a little bit down the street, and now it's clunking like crazy. I feel it through the whole car and through the shifter.

I put it back on the jackstands, nothing is hitting, but it still binds a little at about 1 revolution of the driveshaft. Back on the wheels and back up and it's still making racket. It rattles the car. Back on the stands, nothing is obvious, except I see the drivers side axle shaft seal leaking a little bit.

What's up?

The fluid I put in is Mobil 1 synthetic, and I added some Limited Slip additive. Not GM fluid with GM additive, but I wouldn't think it would make that big of a difference in a straight line. This sounds horrible. I can try changing fluid back to GM, but not sure if that's my problem.

I'm afraid this is about to get expensive...

 

Never rotate the tires with the wheels hanging down. This will bind up big time. The halfshafts will bind up. Hopefully you did not do any damage. Put the car back on the ground and roll the car back and forth. There should be no binding up.

 

It's definately doing some binding on the ground. With the wheels hanging I never rotated a full rotation, just enough to move the driveshaft to get to all the u-joint bolts.

If I did some damage, what would it be? half shaft u-joints? side yoke? C-Clip?

I'm afraid to drive it at all like it is.

I also just tried this: I supported the trailing arms on jackstands so that they supported the weight, and the halfshafts were near level. When I rotate the tires, the move in the same direction, and I could get to a point where they didn't want to move anymore. if I move back and forth again they could get past that spot.

Could this just be clutches sticking, or something worse like a chipped gear or a loose c-clip catching on a gear?

 

So after a night to sleep on it, I thought back to all things I changed:

Driveshaft u-joints - Possibility, but I didn't just hammer them in myself, I had a machine shop press them in/out

Pinion Seal - No way this could cause what I heard and felt

Pinion nut tightness - I took this back to the exact original spot. At worst if I overtightened, there might be a bearing noise.

Rear End lube - This is the one place where I didn't follow what most on here said. I used a synthetic and some non-GM limited slip additive.

Today over a long lunch, I got new GM lube and GM additive. 30 minutes later I was driving around the neighborhood. No crazy clunk/binding. A little vibration that seemed to go away. Did some opposite circles in a cul-de-sac.

I'm going to cautiously believe lube was my problem.

There's still the matter of a leaky side shaft, and likely excessive end play, but that may have to wait until I'm ready to drive the car with some regularity. For now it's a weekly spin around the neighborhood keeping everything working until I get further on my paint prep...

By the way, a search that gave me lots of threads about clunking, and most resolved with the correct fluid, is what let me sleep last night.

 

Did you index the drive and half shafts? They should be installed the same way they came out.

 

Half shafts were not pulled, and I did mark and re-install the driveshaft (and pinion yoke) in the same place that they came out from.

 

Makes no difference. The shafts will turn at different speeds around corners. They will be out of sync the moment you make a turn. The shafts are the same end to end so that will not matter if they get turned around either.

The clunking could have been fluid related. Keep driving and keep your ear to it and see if it comes back.

 

Not to each other yoke-shaft-pinion should be inline the same way they came apart

 

I did a little more driving after work. Everything seems OK. At least on my little trip to the corner gas station to feed the hungry monster. I'm still amazed at how well this thing runs, after sitting 17 years and only my poor skills to get it going again.

I do need to start planning the rest of the rear end maintenance. Driver side sits lower, and bottom of tire is kicked out. I need to replace all the rubber bushings, and while I'm at it change the side yoke seals. Maybe time for a new spring, or maybe I can get the ride height where it's supposed to be with just bushings and bolt adjustment.

 

So, the next time I catch a little air I will have damage? Guess I was lucky the last 50 times.