Differential side yoke end play

[Tom Sarno]

Would anyone know what the specs. are for the differential side yoke end play. I currently have .041 and .028. Also, is there a spec for the distance from the inside shaft end to the c-clip groove. I would like to determine if the play is a worn yoke, side gear shim or clutch pack.

Thanks in advance for the help.
Tom S

[Joe L.]

Re: Differential side yoke end play

Tom-----

There is no GM spec that I've ever been able to find. However, from experience, I'd say that yours are well within service limits and you should have no problem, at all.

[Joe C.]

Re: Differential side yoke end play

Tom:

I assume that you have the Shop Manual for your 1974 Corvette. I was not able to find any side yoke end play specs. As far as "c" clip to stub end dimension, I can tell you that yokes are routinely reconditioned by refacing the end, and then re casehardening, so this dimension can vary. The critical factor, when evaluating your diff, is the 40-70 ft-lb torque test as per your shop manual. The combined wear on the stub axles and clutches will cause your positraction unit to essentially act like an "open" rear.
If you find that this reading is out of spec, I would suggest a full rebuild of your carrier and posi unit.

FWIW: Before I rebuiltmine, I had end play in the .045" range, both sides, and no positraction. After the rebuild, my clutch reading is now 75 ft-lbs, and the stub axle end play is .003".

Joe

[Craig S.]

Re: Differential side yoke end play

Tom - as Joe Lucia mentions, there are no published specifications. I have taken two rear end rebuild classes from Charlie Smith at Bloomington in the past several years, and he has rebuilt thousands of these rear ends. His advice in the class, was once you get to around 0.030" play, the stub shaft and/or clutch packs are getting to where he suggests a rebuild. The original older shafts had a deeper and more uniform case hardening, and tend to last better than the GM service replacements from the late 80's up...according to Charlie, he has had some issues with those having a poorer surface hardening that is not as deep and tends to wear through easier. Once the hard surface is worn through, they wear VERY fast. Tom at International Axle builds an outstanding and strong axle, CNC milled in Dayton, MN at his facility. I toured it and was very impressed. He also uses a very high grade steel, and pays attention to careful case hardening. The reconditioned axles may be good too, they replace the end with a hardened insert that should prevent wear through. Anyway, just some thoughts from the classes....Craig

[Duke W.]

Re: Differential side yoke end play

No one else seems to have ever found a side play spec, but I'm sure that I found one in a mid to late sixties Chassis OVERHAUL manual that had the overhaul procedure for Corvette axles including positraction. The spec is not in service manuals.

Also, there are three shims available that are installed at the ends of the positraction clutches to achieve the correct end play, which is a few thousandths.

Most end play growth in service is due to clutch pack wear, but severe cases of end play wear can be the yoke ends.

Like Joe said, the spec that really determines the health of the positraction unit is the breakaway torque spec.

Duke

[Gary B.]

Craig: quality of reconditioned stub axles

Craig,

As far as you or Charlie Smith knows, are all the reconditioned stub axels
with the hardened insert or button of the same quality? Do you know if all of the
reconditioned stub axels are made by the same company and then simply
resold by different vendors? Do you know who has the best price on these?

Gary

[Craig S.]

Re: Craig: quality of reconditioned stub axles

Gary - I honestly don't know, and Charlie didn't really comment, other than, like Joe, to say it was a good way to go. In my travels at Bloomington and Carlisle over the last several years, I have looked closely at many vendors selling these, and they do seem to vary slightly. In my typical anal nature as a perfectionist, I noted some exhibited an ever so slight misalignment mof the splines on the actual hardened end, and some have a more visible joint where the hardened end is installed. However, chances are good none of this will really matter in terms of longevity, as long as the quality of the insert is correctly controlled and hardened well. I know Lonestar Calipers has always had large displays of may calipers and axle parts, in fact, I believe they are the supplier of the new GM Restoration calipers, and they supply others. I can't remember if they sell directly other than at shows, but I suspect their rebuilt yokes would be just fine....Craig