C3 (or C2) Differential Crossmember help!

[Wayne S.]

Help! I'm plunking away on my new-to-me '71 and I'm in the process of re-installing the differential and differential crossmember. I've lubed the sombreros with silicone grease, and I've loosely installed the pinion mount to the frame. But I cannot get the bushings to seat on the sombreros. I'm hesitant to pull it up on the fastener threads. I've tightened the fasteners to 30 foot pounds and I chickened out to go any higher...L-O-L. It appears the previous owner stripped one of the fasteners and re-tapped it to 12-mm (!). Right at the moment the bushings (and consequently the crossmember) are approximately 5/8-inch to 3/4-inch from being seated.

Thus far I've jacked the rear end and crossmember up to the point where the car lifts off the axle stands. I've tried persuading the crossmember with a dead blow hammer. I'm pretty sure I have it installed square, side to side.

Any help with ideas would be greatly appreciated. BTW, the car is a Top Flight car. It's an incredibly beautiful car, but honestly, it's been loaded with mechanical issues. Something out of whack that I might have missed wouldn't shock me...

Thanks in advance folks.

Wayne

[Mark M.]

Can you show with a picture? Normally there is a gap. I checked a 65 here and the top of cross member to sombrero flat is about 3/4. Top of bushing rubber to sombrero flat is close to a 1/2". They don't pull all the way up. A new sombrero may be a part for a car that nice especially since the bushing bolt is a grade 8.

[Wayne S.]

Here's a photo. When I disassembled it, the dimension was tighter. From others I've looked at (and other C2 and C3 cars I've had), I'm pretty sure the crossmember should go up at least 1/2-inch.

[Wayne S.]

Couldn't sleep because I realized I had made a mistake. So I went back to the shop. I had installed an aftermarket reinforcement kit for the crossmember. They use studs for the install. Because one side was now metric, I had a stud machined that was 12-mm coarse thread on the top and 7/16-inch fine at the bottom. Both studs at the bottom are now back to SAE. But the instructions for the kit were hazy. They showed an illustration of a nut, a flat and lock washer in use to run the stud up. But it also stated elsewhere (in another instruction set I found) that not all applications need this extra nut and washer combination. That's where the interference came from. I pulled the rear end for about the fourth time...getting good at it....L-O-L and removed the extra hardware. Bingo. Chicken Dinner! It all fits perfectly. Anyway, thanks for the space NCRS!

Wayne