my rearend rpo is a GU5.Its in an 86 Iroc. the tranny has been changed to a 350turbo and not done properly. Im trying to figure out if my rearend may have been changed somewhere down the line.The stamp on it is 9JA C032 1 . had no responce in the tran treads. Hayes repair guild dosnt even list this number for any year.closest to it is an 85 year with stamp 8JA says its a 3.08 gear. my car has no possi rpo code. with both wheels off the ground if I spin 1 wheel the other one turns. Is it a possi or not?

 

Which way does the other wheel turn-the one you are not spinning? Do you see a tag attached to the differential cover? I found my gear ratio on the ring gear, but you must remove the diff. cover and slowly spin a wheel to check for the stamped ratio. This was on the BW 9 bolt. I am guessing you have the 10 bolt...how many bolts are holding the diff cover on?

 

It's a 10 bolt w/drum brakes. the other wheel gose in opposite direction. I figure it's a stock 1986 3.23 non possi.like rpo sheet shows. Just didnt know if anyone had a more conpleat list of the axle codes than this cheap Haynes book. Don't get me wrong.The haynes is good for the basics.

 

When you changed the rear end fluid, how many teeth did you see on the gears?

Nothing else matters.

 

I havnt changed anything yet.I'm pulling stuff off the car to do a major freshining.Not quite a full restore.Many parts will be just good used parts.I will count them when I get that far

 

You don't usually have to actually count the teeth. The ring gear is normally stamped with the number of teeth on the ring and the pinion too. For example 41-10, "41" is the ring and "10" is the pinion. Aftermarket gears often have the ratio stamped on the ring gear too.