I have an 88 iroc-z with a 10 bolt with drum brakes, thinking of picking up a free 88 trans am, has a 9 bolt bolt with disk brakes wondering if the swap is straight bolt on or mods have to be down, if anybody knows let me know thanks.

I was just considering almost the same swap. I am having someone else do the work but they said going from the drum to the disk brakes is kind of difficult. I have read mixed views on that around the board, but I dont think it would be that hard. You would need to get the right Master Cylinder and Proportioning Valve if I understood correctly though.

Also, the 10 bolt should stand up to more power, but the 9 bolts are easier to repair. Keep that in mind if you have done any power upgrades.

How is Maui?? Was there twenty years ago and loved it...and one of my best friends moved there last year.


PDG

Wow, that's completely WRONG; the 9 bolt is the tougher of the 2 by a long shot, and is harder to work on than the 10 bolt plus parts are rarer. The rear will swap directly in with absolutly no changes, you just have to detach the shocks, control arms, and panhard bar, then detach the brake line at the junction block and swap over. You should really swap out the proportioning valve (up front under the master cylinder) from the donor car as well to match the rear end. I swapped directly over to a 9 bolt from an 87 car in my 1991 and changed absolutely nothing but the e brake cable, it worked out just fine. If you can do any form of car repair you should be able to do this swap.

Aside from what 91 mentions, also keep in mind that you'll be changing gear ratios (for good or bad, depending on what you want), so you'll need to swap the drive and/or driven gears to make your speedo read correctly.

JamesC

Please forgive my misinformation then...I guess what I was told was really wrong then....


PDG

right on thanks for the info, wondering when it comes to the proportioning valve do i have to change the whole master cylinder as well, or can i jus change the proportioning valve, and what do u have to do to the e-brake cable well thanks again for the info

Just change the proportioning valve and make sure you have the parking brake cables for the 9-bolt.

what if your car is an 85 z28 and swapping it with a 9 bolt rear end disk brakes. I originally had drums with the 10 bolt rear. do i need to change anything else listed besides the PROP valve? brake cable?

Only other thing I can think of the brake line fittings may be different SAE & metric. Just so you are aware and don't try forcing something. But who knows they may be the same, GM did some strange change then.

Does the 9 bolt rear have cast iron calipers? If so, you should swap both the master cylinder and prop. valve from the disc car. In 89, both disc and drum cars used the same m/c. The 88 and older disc cars used a different m/c than the drum cars. The cast iron calipers had a different fluid volume requirement as opposed to drums. The newer aluminum calipers have about the same fluid requirement as drums, so the m/c doesn't require changing on them. Btw, the older caliper design is inherently flawed, they're prone to all sorts of problems. You might be better off just sticking with your drum rear until you can find an aluminum caliper disc rear. Another downside to the 9 bolt rears is the lack of replacement parts for them. The posi units in them are notorious for going bad, and the only replacement is trying to find another used one that isn't fried yet.