my rear brakes like to grab........then let go after a while....i am wondering if this is a problem with my proportioning valve????.....i have rear disks btw

 

the calipers are sticking. not a prop valve prob. Either rip 'em off and lube them up real good or rebuild/replace them.

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Kills to date a 3.1 firebird today 2 stop lights in a row.
95 Grand Am
Serveral Honda's
a freinds 91 Rustang LX(I know its a 4 but he keeps trin')

Planned mods:
Soon coming 3 inch exhaust, 1.6 rockers, High flow 'Verter, and Ignition system. Along with a coplete turbo 4.3 swap planned later this year(hoping to get into the 10's..)
Current mods:
Air box bottom completely removed allowing my K&N to act like an open element filter.
Lower profile tires, 195/55/15 front 205/55/15 rear handles better.

Sterio Sony CD head unit and 9 band EQ, Boston acutics 4x6 dash, Alpine 3 way 6x9 sail, California sounds active crossover, Kroiiler 600 watt amp powering the 'pines and Bostons, 600 watt Jensen powering 2 Rockord Fosgate RFZ1812 subs. And all this cost less then $575...

 

I'd replace the rear hoses, then flush and bleed the whole system with new fluid. The "grab and let go" is a symptom of your hoses or calipers being really old and clogged up with stuff. Change the hoses at least...might as well do the fronts if you can, that way everything is new.