I have a 10-bolt rear with drum brakes from an '86 IROC, and a 9-bolt rear with disk brakes from an '89 IROC. The 10-bolt had been upgraded to a 3:42 gear, while the 9-bolt has a stock 3.27 gear.

I am planning on throwing one of these two rears into my '88 350 IROC convertible to replace the 2.73 presently in there. The question is which one? Keep in mind that my goal is to have a strong, reliable rear with disk brakes.

Please feel free to give any comments, suggestions, advice, etc. Thank you ahead of time. - John '90 L98

 

Does either have posi? If the 9bolt does then i would definitely go with that. Actually i would probably go with the 9bolt anyway because of the discs.

 

Go with the 1989 9-bolt rear with the 3:27 and it is a limited slip.
Big advantage is the 11.655 rotors and Aluminum PBR calipers.
Dump the 10-bolt the 89 rear is a much better set up. It should be a no brainer for you.

 

Picture of 1989 9-bolt rear brakes.

 

I went out to the garage to take another look at the 9-bolt rear I have, and there's no way it can be out of an '89. It has the older style calipers, and the disks only measure in at about 10.5". Does this change your answers? - John

 

Not in the least, its the 9-bolt. The big brakes were just a plus.
Hope this input & picture helped.

 

I am going through a similar swap with an 87 9 bolt 3.27 disc rear. It's replacing the 2.73 drum 10 bolt in my vert. I just want to let you know as the owner of two previous early rear disc cars, they rattle like a ****. Almost to the point of making me spend the money on the pbr conversion before I do the swap.... and I DON'T want to spend money replacing brakes that work.

 

Does everyone else have this same opinion about brake rattle? If so, what can be done to fix it? Besides doing a PBR brake conversion, what other brake options are there?