Question: 71 Rear axle binding

[roylindblad]

I've spent hours searching this and other Corvette forums and haven't seen this yet. 1971 Coupe 100,000 miles 270 HP 4-speed 3.36 ratio. The car ran fine, I baby it I've owned it since 1975. All of a sudden with no noise or telltale warning sign, The rear end started binding up to the extent the car is not drivable. I can go 25 feet forward and some kind of friction stops the car. If I "push" it a little there is a big snap and it willgo another foot. Then I can back up about 20-25 feet and the same thing happens in reverse. The noise seems to be from the RR wheel. I had the car towed to my house. I proceeded to raise the car on jackstands under the shock mounts to keep the halfshafts level and the wheels spin freely in forward and reverse. I grab the wheels and check for play and there is minimal play on either side. The u-joints seem to be ok. I replaced a leaking caliper, dropped the car back down and it did the same thing. It seems that when there is weight on the wheels this puts compression on the driveshafts and this results in the "binding". Could this be a RWB or do I have big problems with the differential. The snap could be the posi locking but I had that problem years ago and GM posi additive fixed that. I thought it was the parking brake that had disintegrated (original) but that seemed fine. Any help would be appreciated. I have always been a do it yourselfer but this has me stumped. Thanx for any comments.

 

[Hib Halverson]

This is a new one on me, for sure.

Usually, problems with the limited slip manifest themselves when you go around turns not in a straight line.

I'd first look for a brake or wheel bearing problem. Then I'd recheck the universals. If you don't find anything there, consider opening up the rear end.

With 100,000 on the car, you might as well service all that stuff, anyway.

 

[TimAT]

I'm with Hib- I've been fooling with thsi stuff for some 40+ years and haven't seen that one. Other than something broken in the differential I can't think of anything that would come close to what you have.

I have seen the lock bolt for the crosshaft in the differential carrier break and the crosshaft slide out, but it's usually accompanied by a hole in the case and the oil runs away. And 25 feet is way to far for a single revolution of the ring gear I'm thinking.

When you had it up, and turned the wheels, was the driveshaft turning?

 

[roylindblad]

Thanks for replying. Yes, I had it in gear and the engine running. There is plenty of lubricant in the differential.

 

[Vettehead Mikey]

I think Gary R has seen something similar, maybe he'll chip in.

 

[roylindblad]

More info. This did not happen while driving. The car had been parked for 3 hours and when I tried to drive home, this all started. It does it in a straight line or turning no difference. I think tomorrow I will see how far I canactually go 20-25 feet was a rough estimate. It was surely at least 15 feet. I'll do some calculations and see if there is any relation to rotations of the driveshaft or rotations of the tires.

 

[Txbobcat]

Drop the oil in the rear end and look for shavings. If you have shavings do not drive it or you could grenade it. Also check pads u joints parking brake. I hated to say parking brake but you never know.

 

[GTR1999]

Sounds like a diff issue. If your bearings were bad,that bad, there would be a lot of play in them.
The travel may be a spider issue or a broken tooth from a backed out a sheared RG bolt. I have seen both.
I'm in New Haven if you need help.

 

[73shark]

Any chance it might be the tranny?

 

[roylindblad]

I seriously doubt it. The noises come from the rear end. I have a guy coming sunday to help me out. But he's a retired gearhead who never had a vette. He keeps saying its POSI It's posi. I couldn't check today cuz I have a coolant leak on my other car. Thanks for the suggestion.

 

[roylindblad]

We've decided it is most likely something in the differential. I can go 20 feet forward or in reverse about 3 rotations of the tire. Now I have to decide do I pull the car apart myself or shake the cobwebs out of my wallet and have somebody do it. How big a job is removeing the differential. Some manuals say unbolt the carrier from the end cap,(sound like a big oily mess) or should I pull the whole crossmember out. I'll bring it somewhere or buy a rebuilt one from a catalogue if I do it myself. I am not a mechanic but I did rebuild the engine 35 years ago and it still runs great.

 

[GTR1999]

It's not bad to get them out.Takes us about 2 hours. Remove the exhaust, that is the biggest PITA but a good time to replace it if needed.
I can go over it rather then type it all out again if you like.I suspect a broken tooth. I would not go with an exchange unit but that is your call.

 

[roylindblad]

I've decided to take the diff out myself. I am having trouble getting the carrier out, It is loose but when I try to wiggle it out. the yokes bump into fibergalss and won;t go. I got the bright idea to take the whole unit out with the crossmember but when I removed the two bolts, it wouldn't budge. Is there a trick to get the crossmember out. ASny help appreciated. Thanx

 

[muddywaters]

I see you checked the parking brake, I had to drill rivets out of the rotor to get a look at mine and they were dragging.

 

[Sean77]

Pulled mine out over the winter. The crossmember is a pita to get lose, I used plenty of penetrating oil, and then used a pry-bar on either side to pop it free. I left the two bolts in but backed out a good way so the whole unit doesn,t come dropping down. Then you can get to the 4 bolts on top to remove the crossmember from the end cap. Also changed the rubber bushings on the crossmember. Hope this helps.

 

[GTR1999]

a 3-5' pry bar should do it. Take the diff out with the crossmember. It's possible to split the diff from the cover like some of the manuals say but I wouldn't recommend it. Then there is the old garage hack trick of cutting the floor board over the diff to get to the 4 bolts-again not recommended.
I just put a diff together this weekend in fact.

 

[roylindblad]

Again thanx for all the replies. Well I did manage to get it out without removing the crossmember. I rotated it 90 degrees and it came out ..I'll sure take the crossmember out to put it back. You would destoy the gaskets trying to jockey back and forth. I cannot see any broken gears or displaced RG bolts, but the diferential pinion shaft seems a little loose. and the posi spring end moves maybe one eighth inch when I rotate one of the yokes back and forth. Maybe that is normal, first time for me but hey 100,000 miles. No metal shavings in the oil- I am surprised. The pinion shaft is tight. The side yokes move in and out a bit but I figure the snap rings have to have some play. I sure hope I didn't remove this for nothing. I was in New Haven saturday , picked up my son at the train station.

 

[roylindblad]

Well I thought I'd give an update. I am having the diff repaired. I guess the posi unit was so bad that the guy I have repairing it advised me to buy a new one from Eaton rather than try to repair it. I purchased one part number 19670-010 and brought it to my guy. He said it's the wrong one! How can that be? To make a long story short, even though that part number was etched on the unit, and that is the correct part number, it was mislabeled at the factory. I think it was really for the 4 series unit. Well tonight I am getting ready to start putting thing back together, I check the RWB right side, pop off the flange and th inner bearing is diosintegrated. Using the spindle knocker, I easily remove the spindle. The outer bearing is perfect but tha inner one is toast. Now I feel that the whole problem was really the RWB and not the diff. It rotated freely jacked up and there was no play whatsoever when I grabbed the wheel. It would only bind when weight was on the wheel now I know why. I don't feel bad ripping everything out though. I am doing both RWB's While I have it apart, U-joints bolts the whole deal. The leaking caliper was from the bad RWB so if you have a leaking rear caliper, Check those spindle bearings! Mine even seemed OK

 

[GTR1999]

There are 2 new loaded Eaton posi's sold today, 3 & 4 series. I hope you don't have a lot of power as those new units are not as strong as many believe. They come with fiber clutches,less per side, huge yellow springs,powdered spiders and are assembled in Mexico. Not trying to rain on your parade but I suspect you were not informed of this. Most rebuilder buy and sell them for the profit mark up and the fact they don't have to build a posi. Did you get your old posi back? If the case is not cracked I'll buy it off you. If it is then it's junk, but if the side hole is opened I can make it better then any new or used posi.

For the rear bearings, use only Timken and be sure to have the parts machine fit if you want a good job. Check your spindles if you have them out now, if you use a vendor some will call and tell you the spindles are "bent" which is about as true as CT dropping the income tax!

Good luck, too bad you didn't call me I probably could have saved you some money.