Quote:
Originally Posted by 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
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If it's not a posi (open differential) just leave
one tire on the ground to hold it from turning.
Then go through the same driveshaft turning and counting as Gregg has outlined.
In this instance (open diff) use
2 full turns of the wheel that's not on the ground instead of only one turn with a posi, due to the 2:1 ratio of the differential side & spider gears.
Myself, I always turn the shaft instead of the wheel, same outcome.
There's really no need to remove the cover to check your rear gear ratio. If you have a rear end with a drop-out center section (the popular Ford 9" would be one) then there is no easy-to-remove cover like on a GM 10 or 12-bolt rear, counting the turns of the driveshaft is always the easiest way.
