I have a 95 F150 4x4 351. I've been told that I have a 8.8 31 spline rear. How do I confirm this and find out what gearing is in the rear? Is it a code on the door pillar ar a tag of the diff. cover?

Thanks

 

If it's a 95 F150 it has an 8.8 31 spline axle.
Look for the axle code on the vehicle ID sticker. The most common are:
18 = 3.08 open
19 = 3.55 open
H9 = 3.55 trac-lok

 

H9 = 3.55 trac-lok is that posi!?!?! Because I had one I think and my clutch disks in the rear end broke off and now I don't have one. So now just one tire spins.... frig.

 

That is Ford's version of a posi but it is a limited slip diff. not a locker version. Code on door does let you cross reference but tag on rear also has codes and actual gearing. If somebody has changed gearing, like before you bought truck, the tag on rear MAY be up to date but nobody changes the door tag.

 

"Posi" is GM-speak. We don't use that kind of language on this board. Both are simply trade names for a limited slip differential.

 

Door sticker says Axle
H9B

Is this the right code? Is this the Trac-Lock??

Thanks for the help

Chris

 

Right code & trac-lok

 

WOW glad I asked I was looking to put a limited slip into it. I work construction management and can play in the mud at work but also needed good street manners. Does anyone know how these rate off road or should I still save for more?

 

Maybe a question for the 4x4 dorum but should I first change gear ratio. would this affect the trac-lock?

 

Unless you're going to a much bigger tire size or are looking to tow quite a bit, I wouldn't change your gears. 3.55's give good power and are still driveable on the street. If you decide to, changing your gears won't affect your LS, in that you can still run LS with your new gears.

 

There are better LS units, depending on how well your's works. Changing gear ratio should not affect it. You will have to pull the differential out to change ring & pinion (gear ratio). And if you change to a different LS carrier, you'll have to pull it out again. I'd decide on what I want and save for it all at once. Especially, if you need a shop to set it up and the truck will be disabled. Why go through it twice.

 

Last question I'll ask in one post but I have 31x10.5 now if I went to a 33 will I need to change gears??

 

You don't have to change gears. Power application will be reduced as if going to higher gears. You have to decide why and if you need 33" tires and how you want the truck to run. If you'd like to keep acceleration same and engine rpm same on hwy then you have to change your gear ratio to compensate for larger tires. You can also lower the gears without changing tire size to increase rpm or towing ability (also reduces mpg).

 

Thanks