We put a rear end in my RS from a 1985 IROC-Z with disc brakes. we swapped the master cylinder and the proportioning valve from the IROC and scrappeed my old drum ones. Did we do right? This took some modifications to the brake lines that go into the master cylinder, and the emergency brake cables, but we made it work. it stops great now, but I was reading the post on 1LE brakes, and I wanted to make sure I wasn't supposed to keep my old components like you do when you upgrade the fron brakes.

 

I've done the same swap. In my case it was a 88 Iroc rear end for my 90 RS. I'd keep your old components. I don't think it was necessary to swap master cylinders or P.V.s. But if you plan on keeping the older style disc rear (pre 89) then you still need to change one item. The parking brake handle assembly needs to be swapped for the older style. Yours doesn't have provision for adjusting the tension. The older disc brakes have a threaded rod that allows for adjustment at the yoke where the 2 brake cables attach. Go to a Pick-A-Part and get the entire assembly and swap it in. If you are planning to swap the rear discs for the newer and larger rotors and aluminum disc calipers then you won't need to do the parking brake swap. Lon

 

I work at a parts house, and I looked up the part numbers for disc vs drum brakes on the proportioning valve and master cylinder. They are different, and I was told that you should never ever use a proportioning valve for drums with disc. That is why I swithced them. Does yours stop evenly??? If so, then I may have done all that work for nothing. As far as the p/brake cable assymbly, I kept my '92 and it works fine, I hooked the '85 cables to the '92 assymbly, and lost a little length, but it is still self adjusting, and it works fine.