how to tell if i have a posi rear.

[Hazzmatte]

my 8.5 rear in an 86 cutlass 442 will spin both wheels during a burn out. But when i had it up on a jack and spun the wheels by hand the wheels moved in opposite directions (one wheel spins forward and the opposite wheel spins backward.) I always thought that a posi rear both wheels whould spin in the same direction when up on a jack.

Any one set me straight here?

 

[Bonnewagon]

Pull the cover off and have a look-see. You were due for an oil change anyway, right?

 

[o ARC ATHEISTxX]

You have a open rear end. When your brakes have even pressure and you do a burn out it a straight line you will spin both tires because you're distributing the power close to 50/50 per axle.

 

[richp85elco]

spin the wheels using the drive shaft and they should both spin the same way.. if you can leave the wheels a little on the ground so there is some resistance so it seems like the wheels are slipping it should engage and both will spin in the same direction if you do have a posi, mine does the same as yours if i just spin one wheel but its a posi with 3.73's.

 

[pontiacgp]

Pull the cover off and have a look-see. You were due for an oil change anyway, right?

X2, if you don't know if it's a posi then you don't know the condition of the oil... people tend to ignore the rear end oil but it can rob you of power and gas is it's neglected

 

[Hazzmatte]

spin the wheels using the drive shaft and they should both spin the same way.. if you can leave the wheels a little on the ground so there is some resistance so it seems like the wheels are slipping it should engage and both will spin in the same direction if you do have a posi, mine does the same as yours if i just spin one wheel but its a posi with 3.73's.

Did this today. Spun the drive shaft and both wheels moved in same direction. Thanks rich85elco

 

[JBreu]

There you go..Posi it is 8)

 

[pontiacgp]

spin the wheels using the drive shaft and they should both spin the same way.. if you can leave the wheels a little on the ground so there is some resistance so it seems like the wheels are slipping it should engage and both will spin in the same direction if you do have a posi, mine does the same as yours if i just spin one wheel but its a posi with 3.73's.

Did this today. Spun the drive shaft and both wheels moved in same direction. Thanks rich85elco

But when i had it up on a jack and spun the wheels by hand the wheels moved in opposite directions (one wheel spins forward and the opposite wheel spins backward.)

in your 1st post you said you spun one wheel and the other spun in the opposite direction. That means it's an open rear end and not a posi.

 

[Bonnewagon]

Is there a tab on one of the cover bolts that says "Limited slip lube only"? How about the axle code? It's on the front of the right side axle tube.
8.5" 3.73 codes- 3TG,3TE open 3TR,3TX posi (442, GN Opt.)

 

[pontiacgp]

Is there a tab on one of the cover bolts that says "Limited slip lube only"? How about the axle code? It's on the front of the right side axle tube.
8.5" 3.73 codes- 3TG,3TE open 3TR,3TX posi (442, GN Opt.)

and by the time all these tests are done and search for the codes it'd be quicker if he did as you suggested to remove the cover.