I have an 87 z28 with 373 gears but im not sure if i have posi or not how do i find out???

 

pull the cover and look, only 100% sure way to do it

 

in first gear, from a stand still, apply the brakes and start going down on the gas pedal, and then stomp the gas pedal and kinda hold the brakes down untill the rear tire(s) break lose when spinning let off the brake slowly and move forward.
this method is called "power braking" and/or "brakestand"
dont forget to look at ur tach and shift gears when nessasary, do not want to over rev the engine.

this is the best way to test to see if you have posi, because once you bunrout you will either leave two nice sized matching tire marks (posi) or a real dark one tire make (open rear end).

 

md that sounds good but it's not very definative or reliable. i'll say it again the only 100% sure way to know is to pull the cover and look. since that requires getting under the car and getting a little dirty most people look for all kinds of ways to get out of it. there are too many things that may or may not happen to fool you into thinking you have or don't have a posi rear.

 

What are the numbers on the axle tube? Their exact location is 3" to the right of the carrier on the front of the right (passenger) axle tube. No 3.73 gears were factory installed in '87's, according to the Haynes book. You'll have to do a cleanup to get the #'s to show.

 

Ede,
With the cover off and looking at the gears how can I tell if it has posi?

 

Inside the center section you will see a shaft about ¾" in diameter... on the ends of it will be 2 small gears, and to either side of it will be 2 large gears... if there's what looks like clutch plates inside the 2 side gears, and a S-shaped spring in the hole where the shaft is, it's a posi. If you don't see those things, but only the shaft and the 4 gears, it's not posi.

 

All of these ways are good but if you are pretty sure that the rear hasn't been into check the codes in the glovebox. Gov-loc spins like an open dif then locks (and is a piece of junk because it is DOOMED with a real motor) so you can't tell by turning and watching if both tires turn which would be a good method on the other posi.