[OINK 1]

It Should be a posi unit. To tell, jack up both rear wheels, get a friend to help.Place in neutral. If you turn One wheel the other should turn in the same direction, if it does it's a posi !! If it goes the other way , it's not a posi. If it is a posi, now turn the rear wheels 1 full turn and count how many times the drive shaft goes around. 1 full turn on wheels, 2 1/2 on the drive shaft( close enough) it's a 2:41. 1 on wheels 3 1/4 on shaft= 3:23, 3 1/2 turns 3:55's, almost 3 1/2 turns = 3:42 . 3 3/4 turns= 3:73's etc. etc. If it's not a posi, remove cover count gear teeth on ring gear and pinion gear, divide ring # by pinion= ratio !!

Pontiac Gregg