C2 Differential Yoke Slop

[Brian K.]

I have what I consider to be too much end play but also some torsional slop. Is there a spec on these? I have the rear out but not apart yet. Are the yokes shimmed like the pinion depth is shimed to obtain spec? Do the splines wear and create torsional slack?

Thanks!

[Roger P.]

Re: C2 Differential Yoke Slop

I have what I consider to be too much end play but also some torsional slop. Is there a spec on these? I have the rear out but not apart yet. Are the yokes shimmed like the pinion depth is shimed to obtain spec? Do the splines wear and create torsional slack?

Thanks!

Hi Brian,
I completely restored the rear suspension on my '65 last year which all started because of the yoke end play on the rear end. Sometimes, the end of the yoke can get worn and will have to be replaced. In my case, only the retaining clip fell off and the yoke was in perfect condition. I understand that this is a fairly common problem, so you might get lucky, too. While you have the rear end out of the car, you should take a close look at the rear suspension components, including the trailing arms and wheel bearings, to determine if any replacement would be in order. This is the ideal time to deal with this project. Other than the trailing arms, most of the other parts are not very expensive. If you find other issues with the rear end once you get into it, Gary Ramadei is the guy to contact on the forum.

Good luck,
Roger (50141)

[Mike R.]

Re: C2 Differential Yoke Slop

The end play should be about .005. and is adjusted with shims assuming the yokes and pin are not too worn. The gear backlash should be about .008. I think this is what you mean by torsional slop.

I have what I consider to be too much end play but also some torsional slop. Is there a spec on these? I have the rear out but not apart yet. Are the yokes shimmed like the pinion depth is shimed to obtain spec? Do the splines wear and create torsional slack?

Thanks!

[Brian K.]

Re: C2 Differential Yoke Slop

The end play should be about .005. and is adjusted with shims assuming the yokes and pin are not too worn. The gear backlash should be about .008. I think this is what you mean by torsional slop.

No, there is some slack in the splines and the clutches...you can rock it back & forth. Maybe the clutches are shot? How can I tell?

[Gary R.]

Re: C2 Differential Yoke Slop

005 side axle endplay would be in a custom built diff. A used diff will have endplay up to and over .125" on the bad ones. Mostly original 74-79's have this much wear but the older cars can as well. The 74-79's were not correctly hardened and wore out much faster. On the other hand I have rebuilt c2 and early c3 diffs with over 100k miles on them and reused the original yokes, they had only a few thousands of wear on the faces. Once they were installed in a correctly tuned posi some may need to be face ground to setup. If you have under 045" endplay and there are no other issues with the diff I wouldn't worry too much about it. The weak area in the 63-68's are the posi cases & spiders.

There will be play in the splines of the axles and side gears, not a lot but you can feel them. Stock and stock build differentials are pretty sloppy in many respects. I can count on one hand the rebuilders out there that will go to the lengths to correct them,and I'm one of them.

The clutches are probably ok but the break away torque should be about 40+ ft/lbs. Now if the car was abused the splines can twist and shear off. If you have the diff out it wouldn't hurt to check the posi case,gears,and yokes.

I have a lot of threads on differentials on Digital corvettes that will help you and all have a ton of pictures. Just go to DC and look in the C3 tech page.

[Brian K.]

Re: C2 Differential Yoke Slop

Hi Gary,

I was just reading one of your setups. What establishes the end play...the shims under the packs? Everything looks good but that slop. Is it reasonable to just rebuild the posi & not bother with the carrier & pinion bearings? If the clutches are shot, would that emulate the behavior of an open rear? i.e. with the car off the ground & in gear rotating one wheel causing the other to rotate in the opposite direction? BTW, it is a AV unit with a 10/69 assembly date if that matters.

Thank you for the help.

[Gary R.]

Re: C2 Differential Yoke Slop

Hi Brian,
The posi is built to the correct spec for proper operation without regard to endplay of the axles. The AV indicates it is or was a 308 posi. That could be different now though, the only way to know is if you know where the diff came from or open it up.
If you get into the diff, I would replace all the bearings and go through it. Yes if there is a specific problem you could repair it, that is how the old manuals were written but to go through all the work to change one part makes no sense to me. If the bearings are original they will be NDH any other indicates someone worked on it in the past, then you really have to look it over. However one positive is if it's a 69 then it should have the much better 2nd design Eaton posi in it over the 1st design your car came with( if it was ordered with posi).

As far as the posi rebuilding, as I have mentioned for years now, they were sloppy from day one. Yes some were tight others were not. I've had posi springs so loose I removed them by hand. The spec is 001-008 lash on the spiders. Since they were production or common vendor built they could be all over the place in spec, the plates and springs keep constant tension on the clutches, giving posi but also more wear and very common hammering around corners. I never use the plates or springs when I rebuild them. They never hammer and have full posi.

Here's one, a 12 bolt, I built but you can see it has full posi.Turn up the volume to get the full impact!

http://www.youtube.com/watch?v=hkPUimPZwoc

[Domenic T.]

Re: C2 Differential Yoke Slop

Gary,
I finished my original 67 posi rear and found that the shim kit offered was better than the one's I got from the parts department in the 60's with exception to the spider shims and cupped bushings. There were none in my new kit and I finally found them in Michigan (expensive).
where is a good place to get the complete shim pack?that includes what is needed to make the s
I only do my own work on these and have my 63 -3: 36 open and a spare 3:08 from the 70s to do.
The clearances you mention are very important as you mentioned on these if one wants to have them last.
There are more noisy units out there than quiet ones, sometimes I think they put the sloppy ones in with the side pipe cars so the noise would not be noticed as much
I had to do a lot of these on wagons, and cars where there wasn't a back seat or trunk to hide the noise.

I finished the 4:11 posi for my 67 and was glad to read your opinion of what the clearances should be.
I put .015 shims under the posi springs to get the right preasure on the plates. They were not made for posi springs but were exactly the right size. I found them in the 1960's at a surplus store in CA for $ .03 per pound.

DOM

[Brian K.]

Re: C2 Differential Yoke Slop

Thanks for the help Gary,

Without the springs, what causes pressure on the clutches, the bevel on the spiders?

Also, if I go that route, and don't have a surface grinder to get exactly what I need, what do you do then?

I appreciate the help!

[Mike R.]

Re: C2 Differential Yoke Slop

Yes its the bevel on the gears that loads the clutch pack. Leave the springs out.

Thanks for the help Gary,

Without the springs, what causes pressure on the clutches, the bevel on the spiders?

Also, if I go that route, and don't have a surface grinder to get exactly what I need, what do you do then?

I appreciate the help!

[Gary R.]

Re: C2 Differential Yoke Slop

Gary,
I finished my original 67 posi rear and found that the shim kit offered was better than the one's I got from the parts department in the 60's with exception to the spider shims and cupped bushings. There were none in my new kit and I finally found them in Michigan (expensive).
where is a good place to get the complete shim pack?that includes what is needed to make the s
I only do my own work on these and have my 63 -3: 36 open and a spare 3:08 from the 70s to do.
The clearances you mention are very important as you mentioned on these if one wants to have them last.
There are more noisy units out there than quiet ones, sometimes I think they put the sloppy ones in with the side pipe cars so the noise would not be noticed as much
I had to do a lot of these on wagons, and cars where there wasn't a back seat or trunk to hide the noise.

I finished the 4:11 posi for my 67 and was glad to read your opinion of what the clearances should be.
I put .015 shims under the posi springs to get the right preasure on the plates. They were not made for posi springs but were exactly the right size. I found them in the 1960's at a surplus store in CA for $ .03 per pound.

DOM

Hi Dom
You can call me at 203-776-2813 x139 and I'll get you what ever you need so you can rebuild your other diff's. As you noted the shims in the master kits sold by the vendors do NOT come with the correct shims to rebuild the 63-66,67 narrow housings.I'm very selective and make up a lot of my kits from various automotive and industrial suppliers.I grind the shims in the 63-67's to setup the lash I want. I see in your picture you have the wider housing,which is better and the shims in the common kits should have worked with that type. 67 seems to be the transition year if I recall, I think I ask Joe Lucia about this in the past too. I believe I have rebuilt both narrow and wide 67's in the past.
In your picture, I see it's a 4 series case which makes sense since you said it's a 411 diff. What I don't like is the edge of the posi case, you can see it's clearly rough and sharp- like every stock or vendor rebuilt one. You can use it like that but I would radius them to help prevent them from cracking. If it's in the car now then maybe it's not worth it if you don't put a lot of miles on it. I can't see if it's the original Eaton 1st design case or not.
The 63 open diff shouldn't be too bad to do but check the spiders. I did a 65 open diff last year that was never opened since '65 and it had pitted spiders. These are not the same spiders as the posi uses but I had a new set and it's back on the roads of CA now.
The 70's 308 should be in good shape as most were used on low performance automatic cars that couldn't spin the tires at all. They didn't get beat up like the 4 spd diffs usually did. Check the side yokes though, if it's a 74-79 then they're probably not too good.
Have fun.

[Gary R.]

Re: C2 Differential Yoke Slop

Thanks for the help Gary,

Without the springs, what causes pressure on the clutches, the bevel on the spiders?

Also, if I go that route, and don't have a surface grinder to get exactly what I need, what do you do then?

I appreciate the help!

It's important to properly setup the posi when the springs are not used. If not done correctly you will risk locking up the spiders and they will break if too tight or loose. You can call me with your questions, it will save me from typing it all over again.

Here is my thread on posi tuning. It is my opinion and to the point. Hope it helps.

http://www.digitalcorvettes.com/forums/showthread.php?t=77257

[Domenic T.]

Re: C2 Differential Yoke Slop

Gary,
Thanks I'll give you a call when I do the other diffs.
Setting these up is not a job for amateurs, or 1st timers. The older third members were much easier for me that were on the C1s
Your artical was good and I now wish I would have did a little grinding but it was road tested by me when I was younger.
I'll beat it a little but the days of racing my shadow are getting few and far as the penalties/violations are not so good.
I was mentioning the noise that the diffs made that were improperly set up. I was told that used car lots and some mechanics would put oat meal, banana peals, saw dust, grease, or whatever in the oil to muffle the noise.
I traded my beaten 411 for a 336 so I could drive cross country at a decent RPM. The 336 was just rebuilt by a reputable shop and i put it in the night before the trip, It sang on the backlash all the way there and back with out getting worse. This went on for about for about a year till it drove me nuts. I took it out and adjusted the ring & pinion and thats when I decided I would do my own from then on.
I did some warrantee diffs after that when I worked for a chevy dealer BUT all the customer pay jobs that the favored mechanics got were sent out to a shop that did nothing but rears.There wasn't a mechanic there that was willing to take the time or learn how to do it right.

DOM