So I have spent the better part of a year now upgrading the entire rear end of my '66 Chevelle. The Right Stuff rear big brake disc conversion, new UMI lower tubular and adjustable upper control arms. New KYB KG5507 shocks. Same springs.
When I set the length of the adjustable upper control arms, I made it the same center-to-center bolt dimension as the old stock original ones, to start. The lowers are tubular, non-adjustable.
I had completely removed the rear axle to do the other upgrades, but re-installation was a non-issue. Until I tried to connect the driveshaft. My exhaust has an H-pipe configuration with a cross-pipe running under the driveshaft. When trying to connect it to the rear differential, it was very difficult. It turns out, it was severely rubbing on this exhaust pipe. I finally got it, but figured I am going to have to remove this H-pipe to set the proper pinion angle. I wouldn't have thought it would be any different, since I set the upper arms to the same length. I also verified the lower arms were the same length as original. All new bolts are still not tightened yet on the control arms.
Then, the second thing I noticed was the the coil springs didn't seem to be compressing as much when I placed the jack under the differential and raised the frame off the jack stands. I thought at first it was the shocks, so I removed the lower bolts from the axle, leaving the shocks to just dangle, but not much of a change to ride height.
When I installed the wheels is when I knew 100% something is off. There is now about a 3-1/2" vertical distance between the top of the tire and the wheel well opening. It's like I have air shocks from the '80's on
Before, the tires sat just up inside of the wheel well.
Any thoughts? I know, everything is new except the springs. So lots of things have changed. But I can't explain it. My springs are well oriented and seated in their upper and lower pockets nicely. Everything else looks good. So I can't figure why the rear won't tuck up in the car better. If I could remove that 3-1/2 inches (!), I bet my pinion angle would be much closer to where it was before too.
Thanks for any info you can throw at me.