Been tinkering with this C3 for about 11 years, 2 years ago I took it for a ride just to have the rear blow on me at 60mph. Needed a winter project so I put it on the lift and dropped the differential. On initial inspection it appeared that before I aquired the car the diff flew apart and someone had done a backyard repair. The case previousely had holes blown in it and instead of replacing the case, it was patched as can be seen in the pics.Gotta give credit, it held a long while. When I opened it up the problem was obvious...the bolts and lockwashers that secure the ring gear had sheared off and went threw the case in the exact same spot that the patch was in. Commen sense tells me that is what happened the first time it blew apart. I am running a stock 350 with an M20 Tranny. Is this a common problem with C3s??? Is there a solution??? These things are not cheap. I found one that has been sitting on a shelf for 30 years for $500 which was still functional but in need of a rebuild....which I can do but it just seems odd to me that the same problem happened twice. Would like to avoid on the 3rd go around. Any advice appreciated.

 

That is not common to blow out a hole through the housing. Many posi cases have imploded but typically are contained within the diff. The housing, cover, and posi case are trash. Get another used diff, inspect it before you buy it and build it. Market price rebuilders pay is $250-$350 for a complete, out of the car diff. Anything over $350 may be high but depends on the diff. I would not trust a used diff as a plug and play, you have to go through all of them and should build them to application. That diff was abused and failed, there were issues with all of the 63-82 diff's, some were better than others. Don't buy one because it was SHP or BB diff thinking it is stronger, it is not.

 

what year?
here is a thread on my 79 rebuild and what to look out for including ARP bolts NOT to use

. I do not recall any lock washers, or any washers at all..

 

[QUOTE=interpon;1609200195]what year?
here is a thread on my 79 rebuild and what to look out for including ARP bolts NOT to use I do not recall any lock washers, or any washers at all../QUOTE]

What issue did you have with the ARP RG bolts? I use them all the time and have in a LOT of diff's I've been without one issue?

 

Good info...The only issue I have is to find out why this thing flew apart twice in the same way. Once I recieve the core that I bought I will compare the two. The core was $345+&120 in shipping. If there are no lock washers on the bolts then that was just the prevous owners attempt to fix the problem...which didn't hold. All the bolts used had signs of working loose or shearing completely off. I realize that I will have to inspect every component on reassembly.

 

[QUOTE=GTR1999;1609200254]remember on my 79 they were too long? i went with the original bolts and loctite. For whatever reason mine were shorter and ARP said they do not make them shorter. BTW Gary.. almost 4 years later that rebuild you coached me on and tuning without clutch pack springs has been outstanding. end play fix really improved handling in sharper turns at speed and zero noise with no leaks. Advice to OP.. watch out and measure hole depth.. ALSO check your axles for wear at ends!

 

Ok. Yes when checking any ring gear, new or used, check the bolt hole depth. GM was lousy with QC back then, it is not uncommon to find shallow taped holes in GM ring gears. I threw out GM gears going back to 1967 with shallow bolt holes. Most times the bolt can be faced and fit with a good thread engagement, but not always.

Stock ring gear bolts used hardened lock washers until they changed the bolts to flange heads. The flange head was not a good move since they didn't use any type of thread locker.

I never reuse ring gear bolts.