My LT1 rear brakes came today. Will I need a 4-wheel disc proportioning valve? If so, can I get one off of a 4th gen? Thanks

-Rippin

 

IIRC, in 89-92, all F-bodys used the same Prop valve, disc/drum and disc/disc

so the one you have should work fine

 

Dave,
I hope you're right but I remember reading that Drum/Disc were set up 70/30 compared to Disc/Disc being 60/40.



-Rippin

 

if you need a disc prop valve i have one off a older 3rd gen trans am 10 plus shipping if ya want it

thanx steve

 

If I end up needing one, you'll be the guy I'll talk to Hopefully I can use mine though. Thanks. Hasn't anyone on here gone from drums to discs?

-Rippin

 

I went from drums to discs, and since I wasn't sure about the valve I went ahead and got a J65 (4-wheel disc) valve from the dealer. I wanted a spare one to gut and add an adjustable bias valve to anyway.

I hear the drum valve works fine, but I also hear it causes problems with hard stops (i.e. the front brakes lock up but the back wheels keep pushing the car and you end up going around in circles very very quickly.) I'd say try it and then change it later if you have to.

If you decide to change it, keep this in mind. GM changed the brake lines from standard thread to metric thread in either '90 or '91, so you'll need a metric-thread valve if you want your lines to fit.

 

yeah I sawpped from drum to disc at the end of the summer, I bought a prop valve off of ebay for a few bucks cause I didn't want to chance having the brakes lock up on me

its a very easy swap to do, are you putting just new brakes on or a whole new rear?

 

Whole new rear. Brakes are included but I don't think the prop valve is. I know it's a cheap piece but money's money.

-Rippin

 

My dad swapped his 92 RS from drums to discs and used the same prop valve and master cylinder with no problems. GM used the same ones from 89-92 regardless of drums or discs. If you decide to change yours, you need one from 89-92. Do not use one from 82-88.

 

Just to add some confusion... I swapped to LT1 rear disc brakes when I added the new rear. I DID NOT change the master cylinder or the prop valve. I figured I'd run it for a little while to see how it performs and change over if necessary. In my experience it's a waste of time and money. My rear brakes do not lock up, and the front only lock up in occassional panic situations - they did that before. The car stops noticably better than with the rear drums and I can stall the converter an extra 200 RPM with the rear discs, so they are doing their job.