have an 88 iroc got a rear end off a 91 z28 with 350 tpi with disc but have calipers and brake lines from a 9 bolt but have a prportioning valve from an 88 iroc with disc will this work or do i have to get the proportioning valve from where the calipers came from please any info will help alot thanks

 

Does your IROC have factory rear discs? If so, I'd try it first and see how it does. If not, yes, you'll need to change it to a disc/disc prop valve.

The 91 Z28 will have the same discs as most/all 89-92 cars.

 

Welcome to TGO. I'm not sure I understand. You have an 88 IROC 9-bolt with disc brakes (10.5 rotors and iron Delco-Moraine calipers) and wish to swap in a rear end from a 91 with disc brakes (11.7 rotors and alum PBR calipers)? If so, you need to purchase a first design 1LE combination valve as the one in the 91 will be a second design and will not fit your 88.

http://www.flynbye.com/catalog/i40.html

There are other considerations as well: parking brake cables and speedo drive and/or driven gears if the new rear as a different ratio than your current one.

The braking systems between 9- and 10-bolt rear ends are the same, so take a peek at the link below for more info:

https://www.thirdgen.org/forums/tran...-10-bolts.html

JamesC

 

Thanks for the welcome! Sorry for the confusion i under stand why. My car is originally drums and im putting a 91 Z28 diff with disc but the calipers, brake, hose, and brake lines are from a trans am 9 bolt rear end. wanted to get the propotioning valve that hawkthird gen sales but it says its for a 91 -92 . Could i still use this one . i think the calipers came off an 89 trans am. Should i look for the one off an 89 trans am . thanks again for the welcome and really appreciate any advice

 

[QUOTE=irocdls1;4897786]Sorry for the confusion i under stand why. My car is originally drums and im putting a 91 Z28 diff with disc but the calipers, brake, hose, and brake lines are from a trans am 9 bolt rear end. wanted to get the propotioning valve that hawkthird gen sales but it says its for a 91 -92 . Could i still use this one . i think the calipers came off an 89 trans am. Should i look for the one off an 89 trans am ./QUOTE]

If the calipers are from an 89 TA, the calipers would be single-piston alum and require the first-design 1LE valve (which will fit your 88 lines). If the calipers are iron, you need a disc/disc valve from, say, an 85-88 car. Make sure it's not the cast iron, but the alum type. Pics in the 10-bolt FAQ I link to above.

To verify what calipers you have, check my vbGarage (garage icon next to my online status, lower left). If your rear calipers look like mine, you need the first-design 1LE valve. If yours look nothing like mine, you need the valve from an 85-88 disc/disc car.

JamesC

 

yes my brakes look like yours so u think i can use the one that hawks sales even though it says its for 91-92 if not where can i get the one i need . brake lines hoses,and calipers came from an 89 tA

 

The 91-92 1LE valve won't fit your car. I link to the one you need above.

JamesC