Rear End Clunking in Reverse - Clutch Packs?

[73 Mike]

More looking for edgumucation than anything else.

Had a nice, long drive yesterday with a couple of the local vette guys. Had a great run. We met up at a friend's place and I parked on his driveway to celebrate the fact that my car currently isn't leaking anything. I had to back out of his driveway and make a couple of reverse turns to get in line and got some fairly substantial rear end clacking. I suppose it could be the half shaft U-joints and will check but the consensus opinion is that it's the pumpkin. I'm told that the first step is to drain out as much fluid as possible and replace it taking care to use the GM additive.

My question is how would the clutch packs, which presumably are the cause of the clacking, know that the car is in reverse? It isn't obvious to me how the issue would only happen in one direction.

 

[big2bird]

Mike, Check the snubber bushing, the D/S u/joints, and maybe pinion backlash.
Drive it in figure 8's to see if it's the clutch pak.

 

[GTR1999]

Mike
Do as Jeff said and check the snubber and joints. If you have posi chatter it will show up most likely when hot and you start up from light or stop sign and tunn. The inner wheel side clutches will not slip enough and chatter.

If you had a pinion seal leak for a while then the oil will have dripped on the snubber and broke it down. The diff will actually move and cause the clunk. If you see any rust dust at the joint caps that is also a bad sign. There should be no play in them.

If you have excessive diff side yoke endplay then that could be the posi set up or worn yokes.

Gary

 

[73 Mike]

The snubber is less than six months old. I'll verify that it's tight but I don't think that's the issue. The drive shaft u-joints are less than two months old so they had better not be bad. The half shaft joints are of an earlier vintage so they are more suspect.

I definitely have worn yokes. The drivers side one at least has neighborhood of a half inch play or more. I chickened out at that stage because I suspect that it would have come right out. At the least, I'm sure that a retaining ring is floating around in there.

Thanks both for your suggestions. I've got an appointment tonight but I'm supposed to be off work at noon and will look after that.

 

[GTR1999]

Mike
you have my contact info, call me and I'll go over your questions on the diff. 1/2" endplay is pretty bad the clip is gone for sure since the distance from face to groove is only .187"
73 diffs are pretty good overall, they do have lousy side yokes and clutches. It might be time to open it up and take a look.

Gary

 

[73 Mike]

Mike
you have my contact info, call me and I'll go over your questions on the diff. 1/2" endplay is pretty bad the clip is gone for sure since the distance from face to groove is only .187"
73 diffs are pretty good overall, they do have lousy side yokes and clutches. It might be time to open it up and take a look.

Gary

Thanks Gary,

Was planning on giving you a call. I'm going to check to see if the U-joints are bad but I've known for a while that the diff needed work. I can't really imagine that all it needs is a couple of hardened yokes and clips. Just not looking forward to the down time. I would think that when I open it up and look inside, it'll have to go into a crate next :ill:

Mike

 

[73 Mike]

Well bend me over and...

Haven't I always always always said always do the easieast and cheapest thing first?

Yesterday I jacked up the rear end and gave the U-joints a really good going over. They look like they have been on there a while but I couldn't find any slack in any of them. This morning I went ahead and removed the spare tire tub and was getting ready to call 1-800-write-Gary-a-big-check-for-a-rebuild when what should I see?

The nut fell off the snubber bolt. :banghead:

Thanks both for your help. I'm still going to call Gary as I'll have to deal with that minor "yoke ready to fall out" thing, but at least now I can wait until after the next Bird run.