RPO codes include J65, GU5, and G80. 5.0 LG4. 5 speed. 86k for mileage. Casting # on diff is 22522878. Built 2/87. No G92.
Is it possible that this car came from the factory with rear disk brakes and a 10 bolt rear end? 3rd owner so you never know what went on with the car. I was hoping to find a build sheet when I tore out the carpet.

 

Of course. RPO code J65 is rear discs; GU5 is a 10-bolt ratio code, one of the lower-number ones. The 10-bolt was the only type of rear available in 86 Camaro.

 

I had some people tell me it had to be a 9 bolt if it was an IROC. Just wanted another opinion. It all looked factory to me!

 

Just noticed….

 

I had some people tell me the Earth was flat too. Didn't somehow make it so.

The 9-bolt was used in Firebirds (T/As specifically) starting in 85, but for reasons known only in smoke-filled back rooms somewhere at GM, it wasn't used in any Camaro until 87. So in 85 & 86 all IROCs got 10-bolts. After that, for a year or 2, many if not all IROCs got 9-bolts; then after that, for the last couple of years of GM IROC existence (Dodge bought the contract with IROC as of 1 Jan 1990), there was a mix, with mostly the lower powertrain options, like TBI 305s, getting 10-bolts.

Needless to say, both rear models will bolt right into any of these cars, or for that matter, up through 2002. From there it becomes a question of brake and wheel compatibility. The 88-back crap brakes and the 89-up good ones are different systems in many ways besides just the calipers and 93-up wheels have a different offset because the rears in those cars, while otherwise the same as ours, are a different length. I have seen pics on this forum of a 9-bolt with drums from a usually reliable individual, but this seems incredibly uncommon, and I have never seen any such in person.

 

My 85 has a nine bolt. I've owned it since 1992, and I know it is original. I was friends with the original owner.