Hi Guys-
I've been hearing a squeek coming from the rear of the trans tunnel and assumed it was the speedo cable. I just replaced the bearings in both rear wheels about 5000 miles ago so it can't be them...
When I put the car up on the Max jax I tried to shake the rear wheels side to side and no problem. However, holding the wheel top and bottom and pulling top while pushing bottom and then alternating pushing top and pulling bottom there is over a half inch movement !!?
Instant panic ! Same both rear wheels. I've owned several C-3s
and have never seen this before. I immediately bought new bearings and seals and shims and proceeded to rebuild right side first. Factory spec is .001" to .008", this one was .015" so AHA the problem. I reshimmed to .005" and reassembled. Still all the slop. Checked with local expert and he told me I didn't have a bearing problem, it is a side yoke problem. So....while shaking the wheel, I watched the side yoke and sure enough it moves in and out over .125". All of this brings me to my question. What are the specs for side yoke end play ( checked every reference I can find ) and if I do nothing about this, am I looking at eventual catastropic failure?
Driving very carefully now-a-days..
The car still drives as well as my wife's new Caddy.

Keep the red side up
and the top down
Larry

 

Your yokes are toast. Replace them.

Someone said GM has a 0.080" max, but that sounds way excessive for me. If I see more than 0.040" I'd start saving my pennies for the diff rebuild.

BTW, recommend you replace the posi clutches as well.

 

And there's the key- the slop you have found does not reveal itself during normal driving, only under extreme autocross conditions.

The wear will not cause a catastrophic condition, but sooner or later the dust shields will eat into the diff housing as the yokes get shorter. There is no wear limit in the GM manuals.

 

Thanks Guys...
By the sound of your responses, I'm not in total failure mode yet. I've given up on autocross because I just can't treat the old C-3 that way. I think TLC and constant adult supervision are in order. I think I'll measure and monitor end play and panic when and if it changes significantly. It just rides and drives too well in it's current delicate condition to tear it apart.
Thanks for your responses !

Keep the red side up
and the top down

Larry

 

What makes you think that? They're toast. Fix it.

 

Van Steel can help remedy your repair. They are a trusted source and have decades of experience.

 

Those side yokes wear very slowly. Good hard ones virtually don't wear. The only time there can be wear is if one wheel is going faster than the other, such as in a tight turn, then the stub end rotates slightly against the center pin in the diff. They are not going to get noticably looser in the near future. Keep it on your to do list, but no sense panicking, the sky is not falling.

 

Maybe some of you missed the "over 0.125" play" part? The diff housing will soon be junk if it isn't already.

 

As the posi clutch discs wear, the endplay of the yokes will increase. If your posi is still working, you are probably all right.
When you had the diff apart, did you notice how much space was remaining on the inner end of the yokes, by the clip groove? If the ends wear off, the clip will fall off, and then you will have a situation. If there is plenty of space between the clip groove and the end of the inner part of the yoke, your clutch pack is worn.

 

There not hard to replace.Gives you a chance to do some cleaning and painting.

 

Now, this does give me pause. It's been about 5 years since I had the rear apart, and then, all I did was replace bearings. All internals looked good and I couldn't find any side yoke lash specs then either. I'm still looking for any kind of GM manual with side yoke lash specs. I am reconsidering and I may go back in. I just hate to have the car "laid up" for any length of time now. Here in Florida it is just now becoming perfect top down weather.

Thanks Guys !!
Keep the red side up
and the top down

Larry

 

If it helps you decide, I'd bet my next pension cheque that at least 20% of all C2/C3s still around have diff yoke clearance similar to or greater than yours and have been that way for years. The owners are blissfully unaware as the car doesn't handle any different or make funny noises.

Yes, someday you'll need to do something but the cost to fix it now or then are pretty much the same.

I'll get around to fixing mine one of these decades..............

 

My '76 has never had the diff opened. The posi still works fine and my yokes move in/out about 0.25". The dust shields don't look worn at all. No weird noises. Also, I can't find a spec for the yoke end play either.

 

This is similar to my situation. I rebuilt the rear suspension and while in there pulled the cover on the differential. The side yokes looked good. No obvious wear on the side yoke ends and c-clips in place. No noise coming from the diff. I simply cleaned up, replaced seals and left it alone for now. .

 

Votes are in and counted....
In the absence of a spec for lash and there are situations out there worse than mine and being driven,for the time being I'll do nothing. I will, however, get it down off the hoist and take a long top down drive, 75 deg and sunny today. I'll probably test the posi clutches a few times just to make sure ( burn outs still my favorite thing at 68 yrs age ).
A couple of days ago the long black stripes were equal in length and easy to do.
I'm outa here headin' for the shop.

TO ALL THE VETS OUT THERE
THANKS FOR YOUR SERVICE!!!

Keep the red side up
and the top down

Larry