I've searched and searched and I can't find the answer to my question. I have a 9 bolt rear out of an 89 GTA that I want to install in my 91 Firebird. The rotors/pads are pretty shot. The rotors that came on the rear measure 11 5/8" diameter. When I search for new rotors online I enter the vehicle as an 89 Trans Am and it comes up with several different rear rotor options. Are all the 9 bolts considered 1LE (J65) performance package? The reason I ask is because there are rotors for this vehicle listed anywhere from $20ea(exc. performace package) to $60+ ea(performance package).

When I pulled the rear I also got the prop valve out of the donor car. My car has disk front/drum rear. When I swap the rear in is there any other modifications I need to do besides installing the prop valve from the donor car, or will my current prop valve work?

Any help is greatly appreciated.

 

9-bolts don't necessarily have 1LE brakes, as a matter of fact, the 1LE didn't really have to do with the the rear brakes, per se.

If the calipers are iron, they are 'non 1LE', pre 89.

If the calipers are aluminum, they could have bee part of the 1LE package or just a run of the mill 89+ car.

You can probably use either prop valve.

 

I have the aluminum calipers, the rear came out of a late 89 GTA.

So, all the 89+ cars with rear disks use the same rotors?

You're saying I don't need to swap out my disk/drum prop valve for the disk/disk one?

 

'89 and up rear disc cars all got PBR made "1LE" rear disc brakes, they're all the same. So yes, all '89-up cars have the same size rear rotors. Your '91 has rear drums so yes, your prop valve is different, and yes you need to swap it. BUT, your '91 will have different threads on the prop than the '89 valve does. I have new disc valves on hand if you need one, LMK.

Ed

 

Thanks for clearing that up Ed. Luckily, when I got the prop valve off I just cut the lines, so all I have to to is put the fittings on my existing lines and I'll be good to go, right?

Here's the one I got off the parts car:

 

If you cut the lines and have the nuts you should be fine.

Ed