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Not unusual and part of a tuned posi. When the posi is tuned it brings in the side gears to close the lash. I keep the cross shaft in place and see how the axle fits. The snap rings are about 066 thick so I would not grind them I grind the axles to size and recheck the hardness. With original axles you might have to get them hardened depending on where the final face to ring dimension it. If you have rebuilt axles the tip is hardened throughout so it's not an issue. Don't put the seals in until you have the axles fit.
Just reading your thread and finding out the difficulties, time and expense involved in your rebuild made me VERY glad that I took the smart (coward's) way out and sent my diff to Gary for rebuilding!
My only time involved was crating the diff up and hauling it to UPS plus looking at the 165+ photos Gary sent showing the progress on the diff! While I don't have the satisfaction of knowing that I did it myself or the knowledge & experience of having done so, I also don't have to worry that I may have screwed it up somewhere/somehow! I know Gary did a great, THOROUGH job.
Same goes for my steering box!
Great job and I hope no more gremlins seek you or your diff out.
If your friend has a Wilson Rockwell hardness tester check the hardness of the axle faces. 50 Rc is good. If the dimension is 190" then there's little wear on them, they don't look bad. If they are soft but in the 190 range you can source a heat treater and have them hardened and tempered.
You can use 7/16-14 socket head cap screws in the bearing caps, it's cheap upgrade. Steel caps use 1/2-13's. A solid sleeve and steel cap are for hard launches, if you are not planning on that you don't need them. You are less likely to break things if you are moving vs a sudden hard shock load. A few passes at the track should be ok but watch for bouncing in the spring, enough will cause issues. When you launch, the rear squats and load moves inward against the cross shaft. IRS should be rigid but that comes at the expense of driving comfort too. Adjustable shocks will help for different use.
You can certainly polish a posi at home just don't do it like some who claim it is polished and only spend a short time on the window edges. If you do it do it right. You will need a good set of grinders, wheels, and a mini belt sander works good. Polish the journals and flange in your buddies lathe. Countersink the flange holes for ARP bolts. Mill the posi pad deeper
You can run GM 1/2 shafts in either size for you application. There is a widespread picture of a twisted 1/2 shaft online, look and you will see other mods as well so the application has a more power and TQ then yours. Typical shaft failure is with the u-joint not the shaft. We broke a Tom's shaft, it was not the shaft but the solid spicer joint sheared under a hard launch, taking out the shaft yoke- the real weak link area more so then the tubes.
Hard use will snap the outer axles at the base of the threads. Some imported axles broke there with little abuse. I know of one guy who had it happen just driving on the street, it wasn't from abuse it was from cheap imported parts of low quality.
So a guy can thru harden a set of gm heavy duty yokes to 50rc for good results? Any idea what kind of material the gm yokes are?
Well for those of you who have read along.
I spent a total of $818 in parts that went into my rear:
Diff Build Costs:
Posi Carrier $300
Ring & Pinion 0
Spiders 0
HD Posi Solid Steel Clutches $190
Timken Bearing& Seal Kit $185
Cryo $100
ARP RG Bolts $35
Cap Screws $8
Total $818
I obviously put a lot of my time in it as well. Roughly 100 hours of labor.
This build goes way beyond a standard $750 "rebuild"
I got a rear that is toughened up considerably vs the standard rebuild. It is not quite a Super 10 because I did not upgrade the axles. But this would run $2500-6000 for labor alone for someone else to do this for me. I wanted it tough, but I also wanted to save the labor and do it myself. I am just glad I had someone to coach me along to make sure I did it right!
Thanks Gary!
I did stop short of adding the $500 30 spline inner axles and $1000 31 spline outers. I stayed with my OEM 17 spline axles since they were all in excellent shape. Let's just hope I am not sorry later!
Last edited by leigh1322; Apr 11, 2024 at 10:23 AM.
So a guy can thru harden a set of gm heavy duty yokes to 50rc for good results? Any idea what kind of material the gm yokes are?
What I remember Gary telling me was that axles from 73 on have very shaky QC and many of them are either too soft from GM or maybe just the hard layer is too thin. In any case they wear rapidly. I have one 77 set that chewed all the way thru the circlip area, that is .25" shorter than they were originally! If they are still long enough, they can be hardened, before it is too late. I have a set of the Tubosan Hardness Testing files, and my barely worn 72 axles test at 57 RC and the severely worn 77 ones test at only 42 RC
I forgot to finish this thread. My axles fit a little too tight and needed a skim cut. Gary says this is normal after tuning the posi, so be aware.
I lost my machine shop buddy recently, so I made a road trip to CT to visit Gary Ramadei.
I spent a couple hours there and he bailed me out and helped me finish the rear.
GTR faced the axles .013” ea. and used thinner select-fit circlips at .062 & .064 vs .066” orig. Final axle back lash was 0.005” L & 0.006” R
Retested axle tip hardness at 50+RC. DONE!
This was one of the few real machine shop operations required (milling the yokes) and was only required because I tuned the posi.
It was well worth the trip and Gary honored me by saying I did a pretty good job, much better and tougher than I would get from a normal rebuild.So if anyone ever needs a real machinist, and rebuilding C3 diffs, rear spindles, and steering boxes all need one, I can think of no one better to call than GTR1999!
Great job and I hope no more gremlins seek you or your diff out.
