How can I tell if I have an open diff or a limited slip in the rear? All I know is I hae the Ford 8.8, 31 spine. The only identification I can see is on the door jam where it says I have axle 18 and there is a metal tag attached to one of the pumpkin bolts that gives two numbers.

9836J
08 88 4K07

Thanks

 

My "guess" is you have the open diff.

I only say that because I have code H9 and I have the LS.

The other "test" is when you leave hard on wet pavement, does only one tire spin or both..........

 

I can live with an open diff because the only reason I ask is because I'm looking into locker options and perhaps the Powertrax No Slip mentioned in a previous thread. One of my buddies suggested I jack up the rear end and see how the tires work together. Any other feedback would be appreciated from anyone. Thanks to all

 

Courtesy of mashie banks, third post down:

https://www.f150online.com/forums/sh...imited+slip%2A

 

Well that certainly does help. Thanks!

 

I think you are talking about when you jack up the rear so both wheels are off the ground, and you spin one of them, the other wheel will either spin in the same direction (LS) or the opposite direction (open).

 

Here is the quote from my friend....

"though. If you have a floor jack you can lift under the differential
pumpkin until both back tires are off the ground. (Block the front
tires!) Then with the tranny in gear, if you spin one tire and the other one freely spins in the opposite direction, it's probably open (or a limited slip with the friction material worn off). If one wheel's hard to turn and it takes a lot of effort to get the other one to spin the opposite direction, it's a limited slip."

 

I've never done the "tranny in gear" method or the other one before. Shouldn't really have to.............

Just turn 'em with the tranny in N and that'll get you the general idea. You may have to actaully "bump" the wheel some on an LS read end to get it to start turning, but once it does, the other should spin in the same direction. On the OPEN one, if you have a buddy around, he should be able to physically hold the other wheel while you are still turning the other.

This has just been from my own experience with a 5.0 GT with an LS rear, my F150 with the LS rear and an LTD with an OPEN rear.

Not saying your buddy is wrong either. Just used a different approach.

Good luck, and let us know how your aftermarket "locker" upgrade goes!