Quote Originally Posted by Matthyj View Post
I agree with Jerry simple & easy, swapping questionable parts with known good eliminates one or the other, just swap them at the mc will work well. If those calipers don't collapse when hooked to the known good side of the mc you have 1 of 2 things that I can see.
1. Siezed brake piston
2. Too big a bore on the rear caliper, you can't move enough fluid to collapse the rear without the fronts collapsing fully. This could be easily confirmed by c-clamping the piston into the caliper and taking some calipers and measuring the inside bore or the outside of the piston of each and confirming fronts and rears are the same.

If either one is the case like mentioned by others you could always swap out the calipers with the same front calipers using them on the rear (no ebrake but your state inspection might require it, my state doesn't might have to use a pinion mount type e-brake) or replace the front calipers with bigger bore calipers that match the diameter of piston of your rear calipers, the gm metrics are available in many different bore sizes to "tune" a system from Speedway.
If the piston is siezed get new calipers.
We are staying tuned here, we are all curious!
The pistons are not seized I know that for sure. The caliper bore size now that another question all together. Looking at the fronts and rear calipers it would seem to me that the fronts hold more fluid because of the E-Brake stuff that's in the rear caliper . Physically they look very close other then the e-brake.
Thanks for your help I hope after testing tomorrow I'll have an answer.