My center section took a dump on my 82. its like the spider gears are welded together. It will roll forward and in reverse but no independent wheel movement. I am in limbo trying to figure out which way to go. Either rebuild the diff. thats in there or to replace just the the center section with one out of another vette. What im trying to figure out is will the 80-82 aluminum center sections interchange? If so is one out there thats better than another. I thought i remebered hearing that a 4 speed car had some stonger parts. The car only puts out like 250 hp at the rear wheels so i dont need a high dollar set up, just something to get it driving again.

 

yes but 82s use the larger stub axles, same as 80 & 81 manuals. You already have the stronger stuff (thicker halfshafts also) 82s have a different gear ratio from the manuals though (granny gears)

What do you mean w/ independent wheel movement? It's not an open diff but a limited slip, if will have to be stronger than the clutches to manually spin one tire and keep the one stationary.

 

It seems like the limited slip is locked solid and wont release. I will try again tonight with a second pair of hands to see if we can over come the clutches in the rear and rotate one wheel without the other moving.
It sure seems like a spider gear is stuck, its not like its a detroit locker.
It also looks like it had been leaking for a while judging by the amount of diff fluid caked on the exahust so im thinking the clutches might be gummmed up or the diff. ran dry and cooked everything in there.

 

How do you know it won't realease? seriously, even when pulling w/ 2 people...you're not going to get 1 wheel so spin w/ the other stationary. It's supposed to be locked up like that. If the gear ran dry the center pin will be blue or even hay colored and it'll be very apparent. Take a pic of the guts, it sure sounds like nothing it wrong.

This is it with a brand new smooth design center pin (the stock has 2 grooves, notoriously for eating into the stub axles)

 

Thanks T.T. you know your c3's and i trust your opinion. I guess i will drop it and take a look inside and see what I got in there. If nothing looks cooked I will assume its ok. Now is it possible to replace the yoke seals w/ out doing a full rebuild or should i just clean it and keep it filled up. Do you have any links or helpful hints on getting this grease bomb out of the car. I will replace the ujoints in the half shafts while they are out but if you have any other suggestions lay em on me.

 

ust been through this myself with my 80, so if it's of any help to you, here's what I can suggest from my experience....

As TT said, you should expect a good resistance to independent motion of the two wheels/halfshafts. I can't quite remember the book spec, but I think you're looking at somewhere around 50Nm applied to one wheel, with the other held, to get the clutches to slip. That's not an exact figure, but it gives you the idea. With new clutches, mine was up around that level when I tested it on the bench.

Getting the unit out is no biggie, you can use a trolley jack to lower it out. I did do mine alone, but an extra pair of hands would have been useful. No more than a couple hours work, including beer/cigarette stops. Doing the side yoke seals should be easy provided the inner ends of the yokes aren't mushroomed over from the constant wear against the centre pin.
The pinion seal is also made easier on these units because the bearing preload is set using a solid spacer (like the rear wheel bearings) rather than a crush sleeve as in the 79-and-back design. That means you can undo the pinion nut and do it back up to the torque spec without altering the preload. Of course winding the 300Nm into that nut is going to take fat torque wrench! But this is only an issue should you need to do the seal.

If the centre pin is worn to excess, unfortunately it'll only come out after the ring gear is removed, which of course means taking the carrier out and replacing the ring gear bolts. I say this, as it was the case with my diff, which has a non-standard 3.55 set in it. For different gear sets, I can't say whether this would be a problem, as perhaps the ring gear may be shorter axially and allow more room to slide the pin out. Should be obvious when you get it open, but it's something to be prepared for...
Can't think of anything else too troubling at the moment, if you're only after doing the seals and perhaps the yokes.

Good luck with it.

Theo

 

Yes, the yoke seals can easily be replaced, jsut remove the c-clips and pull them out, replace the seal, put the yokes back in and use new c clips. The pinion seal can also be done but it's a good idea to scribe a line on the pinion and yoke so you can torque them to spec and line them back up.

 

whats the magic number to dictate diff. yoke replacement. .0625"?

 

 

Well, there's no published spec that anyone's been able to point to. I think it really depends how fussy you are, and also remember that any play here directly affects how your camber changes on the associated back wheel. Although for the most part the yoke will be forced up against the centre pin when the weight of the car is on the wheels, thereby "taking up the slack".
I wish I could remember what clearance mine was at when I put it back together - I wrote it down somewhere but can't find it for the life of me. I do know that it was in the 0.01" sort of ballpark. That was with a new centre pin but the original (I assume) side yokes, which still had a good hardened area on the ends.
I would say .0625 is getting a bit sloppy for my liking, specially when you consider the ends of these yokes, ( ie the bit beyond the circlip groove) are quite a lot shorter than on the pre-79,so you don't have so much room for wear. I would think that up at .0625 you could easily grab the yoke and make it go in and out with a clunk.... not sure that I'd be completely happy with that.

 

well turns out it wasnt the rearend afterall. got the car up in the air and the drive shaft will only move in the forward direction. try and turn the driveshaft for reverse and its stuck. There are some interesting noises coming from inside the 700 transmission too. clunk bang, clank... ugh... once drive shaft was out rear end seems fine.. off to go drop the tranny, for the 3rd time.

 

Urgh, that's a bit of a mixed blessing! Hope it doesn't turn out too costly, I've heard many say that those early 700s are a bit weak. You've got my sympathy, as I'll be taking my TH350 out this easter break, for a rebuild. Little bit worried about what I'm gonna find when I open it!

Good luck!