I have a 03 F150 FX-4 pickup. It is the 5.4L with the 3.55 limited slip rear diff.

I want to put some lockers on it, to make climbing, mud, etc, easier. I think I am going to go with the ARB air lockers. My problem is, I need to know what size the rear end is. 8" 9"? Would someone lend some advice so I could determine this? I know it is a pretty novice question, but I would appreciate the help.

Also, has anyone had experience with these air (diff) lockers? I plan to do both, but seperately. Should I do the front or rear first?

Thanks a lot.

 

You have a Ford 9.75" rear, it's the standard rear for the trucks with the 5.4L.... try finding aftermarket parts for it. There are some, but not a great deal... haven't heard about any lockers. The front is a Ford 8.8" reverse cut, solenoid controlled, vacuum motor actuated diff...no front hubs. I doubt they make aftermarket lockers for the front, even thought the 8.8" rear has lockers, but only in the rear diff version....

-Kerry

p.s.: please, someone, tell me I'm wrong.

 

Apparently, ARB makes air lockers for it. Have you heard of them? It is a push button controlled air locking differential kit, for about $600. You do have to buy,, and install a compressor, but they do reference a part # for the front end you specified, i have.

 

I see the part number for the front in the catalog on the ARB web site.... well kiss my grits. I didn't know the front was a 28 spline.

I can't locate the 9.75" rear anywhere in the catalog. $600 is about what they average, though. The catalog gives a disclaimer about not being complete and checking with your dealer.

I'd do the rear first, unless you want to run the LS until it craps out, then you'll already have the compressor and some idea of what to expect. Figure you're going to spend around $1500 - $1600 bucks for both w/compressor before labor. If you're a do-it-yourselfer (I'm finding less and less of those guys) you save a pretty good chunk of change.

ARB is the only airlocker I'd consider. May want to poll the 4x board. I've been pleasantly suprised by the LS in mine. By the way I have a 10.25" rear diff with 3.73's, the HD version of the F150.

-Kerry