i might be buying a rear end out of an GTA w/rear discs. if i do, do i need the brake proportioning valve (below master cyl.) ? are hey different than the rear drum valves? thanks

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1987 Trans Am
"Tired, old 305"
4 barrel, 2.73 rear
700R4 + B&M stage 2 Transpack
1980 350 Small Block sitting on the stand waitin' for heads.....

Best 1/4 mile time:
16.075 @ 85.52 MPH

Just get the adjustable one from summit. It's like $30-$40. You'll need to do some modifiying if you get the stock, non-adjustable one anyway. But, adjustable is better, anyway.

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'82 Firebird, dead stock, 9 bolt disc rear, over 200,000 miles and still going strong, more to come...
http://www.spinfrenzy.com/stingerssx...easures.html#4

If your existing p.v. has a brake line coming from the front and one from the bottom and is a cast round body (barrel shape) then yes it needs to be swapped for the disc brake p.v. The disc/disc p.v. is machined from extruded aluminum billet and has 2 brake lines coming from the bottom. Also by retaining a stock GM unit vs. getting an adjustable, you retain the brake bias switch letting you know if you have a brake failure or not. Also you can re-bend your brake line carefully to relocate if from the front of the p.v. location to below the p.v. I hope this helps, Lon.