Transmissions and DrivetrainNeed help with your trans? Problems with your axle?
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I have a 1985 Iroc z camaro and it has a 3.42 gear ratio in the rearend. I was wondering why it doesn't have a posi? It is a one wheel wonder. Does anyone know if it was rare to have this option without a posi? It has the 305 tpi engine with 700r4 automatic. I want to install a posi, which is the best one to get?
The reason it doesn't have a posi is it's not your car's original axle. an '85 IROC TPI could only have a 3.23:1, and you couldn't even special-order any other axle ratio with that engine.
It is the car's original rearend. I bought it with 55,000 miles on it. There also was an option of 3.42 gears in that year on the Iroc. I saw it on the bottom of the page when I clicked on (1985 Camaro '85). I also installed a 1989 corvette L98 engine in it. I think I should get 28 spline axles and a good posi for it. I have never had problems with the 26 spline axles and have spun through three sets of tires and I used to do alot of street racing.
you could get a 3.42:1 with the carbureted IROC-Z, but this one is either not an original TPI car, or it's not the original axle. GM never emissions-certified the '85 LB9 with any ratios except 3.23:1 and 3.27:1. Therefore, none were built.
MPFI V-6 LB8 motor introduced to replace carbureted LC1 V-6. It Had similar port injection as LB9 TPI V-8. All manual transmissions now 5 Speeds. 7.5 inch rear end dropped and replaced with a new 7.625 (7 5/8) inch rear end for all Camaros. G92 (performance axle ratio) only available on IROC-Z for 1985.
Mine was a original 1985 Iroc Tuned Port Injection car and I am sure this is the original axle. Disc brakes on the rear and I changed oil in rearend when I bought it and put synthetic 75w90 in it. I am sure it had never been apart before.
Humm, well here's my story. I purchased my 85 IROC (LG4) with 54,000. Someone had swapped out the 3.23's for a 2.77 or perhaps 3.08 with drums--even the 16" IROC wheels were missing. I've never discovered why, though I suspect the Delco-Moraine discs were a problem. At any rate, who knows what, where, and why may have occurred along the line--because the diff fluid had never been changed doesn't mean the rear end is original to the car. Anyway, good luck with your quest.
JamesC
__________________ "There are more things in heaven and earth, Horatio, / Than are dreamt of in your philosophy." Hamlet
"Convictions are more dangerous enemies of truth than lies." Nietzsche
you could get a 3.42:1 with the carbureted IROC-Z, but this one is either not an original TPI car, or it's not the original axle. GM never emissions-certified the '85 LB9 with any ratios except 3.23:1 and 3.27:1. Therefore, none were built.
Read this post there was a shortage of LSD's in 1985. 
