Had the car (1990 iroc, 305)on the lift today and wrote down all the numbers i could find on my rear axle. Here's the long number that was on it(22522676). Does this # tell me what kinda gears i have and if it's a posi or not. I had the car in neutral while in the air and turned one of the rear wheels and they both spun in the same direction. Does this mean i have positive traction like some people have told me? If anyone can tell me what gear ratio i'm running or if i have posi. i'd appreciate it.

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> 1990 IROC-Z (black)
> one of 3000 IROCs with a 305 made in 1990
> flowmaster exhaust
system with mufler bypass
> z-28 spoiler
> blue under car neon kit
> white face inlays
> clear side markers
> check out my site at: http://geocities.com/thickfacek/IROC-Z.html

> email me at thickfacek@nc.rr.com

 

Check under the console lid for an RPO beginning with G (ie GT4). Then check it on the RPO decoder on this page.

 

The axle code will be on the front of the passenger side tube. You'll probably have to use a wire brush to find it. That number you gave means nothing to me.

Unless the diff was swapped out, the RPO codes are your best bet. Not all axle codes will tell you if it's a posi or not. You had it on a lift you could have easily checked for a posi. Turn one wheel forward. If the other side also goes forward it's a posi. If the other side goes backwards it's an open diff OR an Eaton govlock diff. Not as good as a real posi but better than plain open diff.

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87 IROC-Z SuperPro ET Bracket Race Car
461 naturally aspirated Big Block (times are for the current engine)

Best ET on a time slip: 11.447 altitude corrected to 10.99
Best MPH on a time slip: 119.42 altitude corrected to 124.86
Altitude corrected rear wheel HP: 493
Best 60 foot: 1.586

Racing at 3500 feet elevation with a typical race day over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley