i checked the #s on my rear end and it had 6HF which came up as an 88-89 3.08 posi. i thought it was a standard 3.23 because thats what should have come on it. the person that had it before me had a crate motor and a flowmaster exhaust so they might have changed the rear end too. how can i be sure its a posi? when the tires spin usualy both of them spin but not all the time if there is sand or something on the road making it slipery. i'm going to change the gear oil soon so what should i look for when i take the cover off?

 

If you look at the carrier, a posi will have pre-load springs in the center, an open rear will not. The cross pin is missing from this picture, but it shows the pre-load springs.
P.S. disregard the red arrow. Thats pointing to the C-clip which I was highlighting for a different discussion.

 

Are the springs you mentioned the ones outside edge of the hole in the carrier? namely like the one underneath the red arrow? My carrier has the outer springs but a larger metal cross pin lookin thingy is in the way of the rear springs. Any help would be appreciated - I am just tryin to find out if I have an open rear like i orgionally thought or the infamous brokeass posi.

 

If it has any springs at all, it is (was) a posi. Open rears are entirely without springs.

 

Is there anything you can do, short of replacing the unit to repair a faulty posi?

 

http://www.auburngear.com

That's who made the GM OEM differential. Look around on their page, there's a wealth of info; they have a trade-in program, they sell parts, there's rebuild instructions, etc.

 

i took the cover off and its a regular 3.23.

 

Can over size rims and tires cause posi to not function correctly? Right now I have 275/60-15s on forged steel rims (beefy *****). Could that be the reason my posi does not function?