flounder

I am trying to find out what gears I have in the rear of my 87 Iroc-Z with out taking off the rear cover. I was wondering can this be done with the vin number some how?? Not sure if I can use vin number on a website somewhere and they can give me the info. Also I know there is some sort of way to calculate it buy comparing speed to rpm's in drive..if anyone knows how to do that I would appreciate it.

Also is there anyone out there running 4:10's with a 700R4??

87DJP2001

Check your RPO codes for the rear axle on the car. Codes located on sticker under the console lid. If your car is 305TPI Auto the rear is a 10-bolt 2:73.