I have and 89 Iroc 5.7 TPI. I came with standard drum rear brakes. I have an Disk brake rearend out of another 89 Irocz (NOT 1LE). Is this a direct swap or am I going to need to swap the brake booster and master cylinder. I hear that I do not. The part #'s are the same at the local part stores. If you have done this or have any info please help. Thanks, Charles

 

as for the prop valve , if its the aluminum billet machined looking one you should be ok. as for the rear its pretty much a stright cross over assuming you kept the hard brake lines that run L-R of the axle and the E brake cables.
also being its a 89 disk rear, those calipers are the same PBR calipers used on the 1LE option. thats what GM went with in 89 and ditching the iron problematic version. BTW is that a 10 bolt rear or a borg 9 bolt? you can tell if its a 9 bolt by the fill plug in the diff cover, the borg insignia on the bottom of the rear.
for refrence the 9 bolt caliper mount plates WILL NOT bolt to a 10 bolt rear.

 

If the rear is out of 1989 IROC-z it is a BW 9-Bolt with 11.655 dia rotors and Aluminum PBR calipers. Since you did not state the gear ratio they are 2:77, 3:45 (rare) and 3:27. I have made this swap and the only major items you will need are the Porportioning valve and the parking brake cables. Everything ese is a direct swap. Good luck.

 

not all IROCs came with the borg rear, i have seen some with the 10 bolt and the RPO code to verify. he would be hard pressed to find a 3.45 rear as they were on the stick cars. fortunately i have 2 of them and i snag up every 3.45 ratio i can when funds allow.
im thinking since he has a 89 already he might have the correct prop valve, i might be wrong. i concur with 87DJ, its pretty stright forward. be sure to check the E brake cables before ya get 100% done.and make sure the rubber lines are healthy.

 

It's a ten bolt.... the rearend was in a 86 iroc but is now in the 89 with the 89 brake system. Now I want it in my 89 Iroc. I know the rearend will fit it's just the other brake system is what I'm not sure of. The Porportioning valve looks the same on both but I'm going to look for the part # to see if it's that same.

 

in that case i would ditch the cast iron calipers and rob the brake system off of a 93-97 car. EVERYTHING will cross over. caliper plates and all. just snag a prop valve off of the 89 iroc and you should be good. the cast iron calipers will be a PITA. as soon as i get my 83 T/A moved to our new house that car is getting the cross over as well.

 

The calipers are not cast iron

 

oh man i did misread i do apologize. in this case you are pretty much set.

 

what rear end options were in the 89 gta? same?

 

yup, you could get a borg rear in the GTA or the standard 10 bolt.

 

The Values on both the drum brake car and the disk brake car, look just alike in everyway. But the part #'s are different. Any Ideas?