I have my diff out. I have fought with the pinion snubber several times, because the bolts are through and through. PO had punched holes in cargo area to get the out, and I have patched them several times. It seems a stupid setup to me. Why not tap out the holes in the diff to next larger size, and put 4 grade 8 bolts in?

 

I am Ok with you trying it, and let us know how it works! I am not going to talk you into it or out of it. On the stock ones, the crossmember has the rubber donuts and then you have the pinion snubber so that thing under torque is moving, and I think the design kind of just cradles it and therefore no sheer of the bolts. If your snubber is excessively wearing out, then that ain't good. I put an aluminum disc up there, as I don't look to any of my cars for ride comfort. On two cars I have removed and solidly welded the crossmember (race car crap). One caution is for like earlier C2 cars, upgrade the big carrier bracket thing to the reinforced holes later units, if you change the pinion disc to solid. Those things will fracture at the bolt holes, and the later C2 car and C3 got a manufacturing fix of reinforced area around the bolt holes. If you threaded and use bolts I would think the thing would move as an assembly and it would be no different, as I think the slide bolts design is to just ease install and removal. Sometimes if you have to caught the threads, not too easy, while you are holding that thing up. A human needing three arms, the weight of that unit, I see your average mechanic crossthreading threaded in bolts, due to the weight of that unit resting on a bolt as you tighten it in. The slide bolts, you partially slide those in, while wiggling the whole unit, and when you got it, you got it, tag the bolt, slide it thru with hole alignment. Ya I could see threading working, but is it worth it. Damn smart guy punching holes thru the fiberglass, I do stuff like that, drill to the size of a pre-existing hole plug. Pop the plug, do you beer drinking mechanics, put the plug back when finished.

 

I wish they had made a clean hole in the jack compartment, but one is in a corner. I made a fiberglass patch that I have applied "for the last time"3 times! I can see what you are saying about cross threading though, and you might not get another chance. But with the snubber out, those rear driveshaft bolts are so easy!

 

Are you talking the bolts that hold the sheet metal snubber bracket to the diff case? On my ‘64 they used short bolts in the front, 1 from each side and the diff case is threaded. I have just replaced the diff with an assembly from a ‘74 and it uses the long bolt that passes through front and rear. And I could not agree more that it is a bad setup. MUCH easier to get to the driveshaft bolts if you can swing the bracket down.

I don’t see and reason you can’t drill and tap the case to a 7/16” bolt and drill the bracket hold over size since GM used that setup originally. But clearly over time they thought the through bolt was better. Not having worked on C3 cars I wondered if that bolt can be removed on the newer design.

 

If memory serves me correctly; both through bolts are removal on a '76.