This has probably been covered before, but............

I've got an '83 with the stock pegleg rearend with drum brakes. I am seriously considering upgrading it to a posi traction setup at a local rearend shop. And I'd also like to upgrade to rear disc brakes.

So, I found a used Borg Warner 9- bolt disc brake posi rearend out of a wrecked IROC. I also got the master cylinder and proportioning valve off of the same car.
This rearend had it's axle tubes bent backwards slightly (probably by the torque arm in a front end collision). I was told that unless you had a B-W running absolutely trouble- free, it wasn't worth messing with due to the high cost of rebuild parts for the posi unit.

So I got the unit mainly for the disc brake rotors, calipers and brackets. I cut the bent tubes off in case I need to remove the axle ends (like cut the backing plate mounts, actually caliper bracket mounts, off in a lathe or something) to try and weld onto my drum brake rearend. But there are removable caliper bracket mounts too, so can I just use those on my drum brake axle housing ends? The backing plate mount on the drum rear is kind of an offset rectangle and I believe the disc rear bracket mounts on the tubes are more square. Does anybody know if I can just drill two more lower holes in the rectangular shaped mount and bolt the disc caliper brackets on? Or is the mounting and spacing going to be totally different?
I haven't tried to mock anything up yet for this, I was just wondering if somebody has already been down this road before?

Also, I did keep the BW posi center section. Is this worth anything to anybody? The gear oil did show some signs of silvery coloration, even though the car must have been running pretty well right before they found the telephone pole, or whatever in their way. Does that mean the posi is badly worn or is that fairly normal? I just wondered if there is somebody out there that needs one or a part from one.

 

It has. You can mod the axle flanges as you suggest or simply purchase one of Ed Miller's conversion kits.

https://www.thirdgen.org/ls1reardisc

http://www.flynbye.com/catalog/i30.html

JamesC

 

Yes you can drill out the mountings holes, and square the top off. I did this for my 89 that I put 93 Z28 disc on. I even drilled out the spot welds on the park brake cable mount. This is above the driveshaft on the body, all for 125. You will have to remove axle to take the caliper mount off... After you re-drill the pattern it is the same as older 10 or 12 bolt rear ends, Except Impala.. I used my 89 Brake lines, but had to change both ends at the caliper..