I just bought a 71 2nd gen and this is the pic of the rear end....the seller states that it is a 12 bolt with 3.31 gears and posi.....any info you can give me based pff of the pic is greatly appreciated...[IMG][/IMG]

 

well it is a 12 bolt. if you get both back wheels off the ground spin one by hand if the other spins the same way its posi, if it spins opposite its an open diff. as for the gearing youd have to pull the cover off, it should be stamped on the carrier.

 

Good, thanks!

 

The gear ratio is stamped on the end of the ring gear. But you can tell what it is by jacking both wheels off the ground (with a posi), putting trans in neutral, turning a wheel one full revolution, and counting the number of times the driveshaft turns. The number of driveshaft turns is your gear ratio.

 

Awesome, very helpful, thank you sir