G'day...I've read that there is a tag or pressed number on the passengers side of the diff to tell what ratio is in it. I've looked but can't for the life of me see it.

The RPO codes on the sticker in my car doesn't show the G92 which is the 3.42 posi code, but it does show GU6 which is supposed to be 3.42 ratio and I have a posi diff. Are these the same and how can I really varify other that pulling the diff apart what exactly is in there.

If it helps at all, I change to 3rd at about 30-40 before the finish on the 1/4 mile.

305 TPI auto IROC with 245/50/16's

Any ideas or help?

 

I'm assuming you have an 85 iroc? (name). I have an 85 iroc with rpo gu6 which is for 3.42 gears in the rear. If you don't have the g80 rpo code also, then your car didn't come with a posi rear from the factory. (mine didn't) That's not to say it doesn't have one now or even different gears because someone could've changed them. I'm pretty sure if it's an auto, put it in drive and go 70. look at the rpms and that will tell you approx what gear ratio you have. It did work with mine. it's got 3.42's and that's bout where the tach is at at 70 in drive.

 

rgr that..what rpm was yours at 70mph? Other thing, my speedo reads slow...at 53 or 55 (can't remember which one) its actually doin 60mph..had it tested on dyno ages ago..is that a sign the gear ratio has been changed?

edit: the other thing is it came into NZ as a "NEW" car and its only done 60k, so unless it was changed here, but I don't think it was...is it possible for someone to order a different ratio and or the posi at time of purchase back in 85 in the States without it showing up i the RPO codes?