Hi i have a 91 firebrid 5.7.i changed out the old rear from a 2.77 drum to a rear off a 88 posi disc with 3 .27 now my brakes are mess up . so i changed the calipers and master and pads and still i have a low peddal and when you hit the brake s for a faster stop . the pedlel gets lower and the brake light comes on . so now i want to change the propotiong valve and the dealer sold me one for a 86 to 89 rear disc but now all the threads are wrong on the lines to hook it up with . so i would have to change the brake lines as well , so can some one please tell me if am i looking in the right place for the problum or is it something else that wont let me have brakes in my car . lol .i hope someone can helpe . thank you

take the prop valve back and throw it at the salesman who gave it to you. i assume you told them what year your car was? if they gave you the wrong part, its their fault and you should be able to get the right one. it will help.

ook the guy told me i need to one from the year of the rearend so it s the year of the car i need then correect even thou the brake pad s a smaller on th 91 rear and bigger on the 88 cuz thats whats under the car now an 88 thanks

hes full of sh*t if you have a 91 the threads are different, who cares about pad size, you need one from the same year as the car so it fits, other than that i think there are only a couple differnt valves, disc/drum, disc/disc, and 1le, maybe 2 others.

You'll need the 91 model year rear disk brake proportioning valve for correct brake line presssure to the rear calipers. Did you change the master cylinder? If so, why? If you did, did you bench bleed it? The symptoms you describe would indicate that you still have air trapped in the system.

its been bleed to death lol . but the master is the same for all so there telling me and napa .but changed it just incase it was bad im takeing the car to florida i do twice a year . so it sounds like i need to get a 91 rear disc propotiong valve . i guess thanks

1. slow the hell down;
2. punctuation please, it's easier for us to read.

There's more to this issue..I can assume you are using the '88 disc brakes? If so, the '91 disc prop is wrong for those technically. The rear calipers are new, correct? Those calipers are known for locking up and not working. Should you go and get a '91 disc prop valve the one you need is GM P/N 10164112.

I still think you'll have issues until the system is fully bled, a dealer will charge you $35-40 to pressure/vacuum bleed it fully.

Ed

sorry ed im not good at spelling anyways the calipars and pads are aloso off a 88 i had no clue there was ai diferance till after the fact .and was having trouble with then so basily everythingin the baqck is 88 and everthing in from is 91

N/P, no offense.

OK, unless you want to upgrade the rears to the better '89-97 PBR brakes let's work with what you have. Unless you are certain the rear calipers have the recall kit installed, I'd rebuild them and use it. Those rear calipers are prone to freezing up and not working right, the recall kit cures that problem. The P/N for the recall kit is on here somewhere, I don't have it in front of me.

Other than ensuring the rear calipers will work and making sure the system is bled I don't have a proven solution for you right now, but you should still have a tight pedal when the system is bled and your fronts will do most of the work anyway.

Ed

well the rear calipers are brand new from napa thee for an 88 so are the pads so you still think its a bleeding thing cuz he peddels low but works ok kinda mushy but for a fast stop its lower and t he light gos on so what should i do with the prop valve the daeler gave me for a 86 to 89 rear disc the threads are wrong on it so i cant put the lines into it bo