I am looking to upgrade my rear brakes to disc and rear ratio to 4:10. I have a 91Z. I found an old rear off of an 86 Iroc, rear disc, 4:11 ratio. Needs some reconditioning and park brake is kind of a wierd set up. I am not sure of the posi condition. Since they have a different axle sline I would not be able to use my good posi if necessary. I thought of swapping the whole rear out, DO YOU ALL THINK IT WOULD BE WORTH IT??

 

Not even close. First 86 rear discs are garbage. All of the pre-1989 iron caliper rear disc brakes only work about 20% of the time. They're prone to malfunction, and properly functioning drum brakes stop better. About the only positive about them is they look "cooler" then drums.

Second, TPI makes it's power (torque) at lower RPM. Numerically higher gear ratios will just run the engine out of it's torque curve faster. The 6th gear will help a bit, but you're probably not going to see much difference between 3.73 and 4.10 gears anyway. If you feel you need more aggressive gears, make a larger change.

 

the only thing i would throw behind that t56 is a moser 9". only then would i upgrade the gears to 4.10s.

...I can't imagine the TPI system would enjoy the steeper gears tho.