So I have a Regular rear axle and I want to have a Limited slip rear axle and was wondering what the best way to do this. I know I could go to a junk yard and get another axle but is there any other ways????

 

The only way to do it without resetting the gears and not swapping the whole housing is a power trax or something similar. Most handy under a car/truck should be able to install them.

 

Since your truck is a STX, you have the 4.6 and your rear axle is an 8.8" with 31 splines. You can buy just an LS and do the install yourself, it's just a matter of pulling out the old diff, removing the ring gear off the old one, bolt on the ring gear on the new diff, install new diff in housing. You do not need to remove the pinion gear, unless you plan on a gear change while your in there.

There are several LS diffs available for the 8.8, the factory unit (which is a clutch type) aftermarket clutch type LS like the Eaton unit, cone style LS like the Auburn unit, geared style LS like the TrueTrac, mechanical locker style LS like the Detroit Locker, E-Locker from Eaton, and the Air-Locker from ARB.

 

So if I went after market and just wanted to take it to a shop and have them do it what do you think the cost would be? And which one would you choose to use? Another thing i looked at was www.getfordparts.com and they have stuff for the diff but I am new to the whole Diff GAME and was wondering what all I would need exactly? Sorry for being a F.N.G. (**** new guy).

 

Take your truck to an "axle" or differential shop only! Cost to install a posi unit will be anywhere from $500.00 up!

 

Don't know what a shop will charge for an install, probably your first born.

As for which one to choose, that all depends on what you need and your driving style.

If you do basic normal street driving, then the standard ford LS will do, along with the aftermarket clutch style LS units. The Auburn cone style LS is also a good street unit, as is the TrueTrac. The ford units tend to chatter if not setup properly or if they don't have enough friction modifier mixed into the oil, but they are the cheapest.

If you do any off road or dirt road driving, then the detroit locker is a good choice, but they can be noisy on the street.

The E-lockers and air-lockers are open diffs until they are engaged then they are fully locked like a spool. DO NOT run these locked on the street, that's how you snap axles. I've heard that the electric versions, or E-lockers, tend to burn up after a while rendering them useless, a basic open diff.

For general use I would buy the TrueTrac, it's quiet, doesn't chatter, doesn't require friction modifier, and is very durable. They are also reasonably priced, about $400-$450.

If your on a budget, you can just get a ford LS unit out of a boneyard, all the V-6 and 4.6 V-8 F-150's have the 8.8 rear axle going back to 97, possibly earlier. I don't know what the spline count was on 97-03, but the 04-up have 31. Also all V-8 mustangs from 85-up have the 8.8 in them, but only the new ones from 05-up have 31 spline axles, the older ones were 28. The 89-97 T-birds and cougers had an IRS verion of the 8.8 in them and the T-bird Super Coupes had an LS, along with some of the V-8 eqipped cars, but I believe they were 28 spline. Also some rangers had the 8.8, which ones I don't know.

 

i have a different question. I had a little accident a year ago and slid into a sidewalk curb making impact with my rear left wheel. The axel shaft seemed slightly bent as the wheel looked like it had a slight wobble. Anyway, didn't do anything about it until now when the noise is starting. Mechanic says i need new axel, bearing, rotor and seal kits and all kinds of other stuff. My dealer on island is a killer and wanted to charge me $1000 to replace the stock rim that i broke in the accident. Where is a good place to look for used parts?

 

NO, NO, NO!

The ONLY way the above instructions are correct is if the new LS carrier has the EXACT same width as the Open carrier. And this is HIGHLY unlikely as we're talking about thousandths of an inch.

And even if you do happen to get the EXACT same size, you still need to take more care installing the ring gear onto the carrier. It is not all that difficult to "twist" the ring gear with an improper installation. I would go as far to say that its generally easier to install a whole new rear axle.

The only real option for a home mechanic that doesn't have the tools/knowledge for a gear swap is a PowerTrax, NoSlip, or similar. That doesn't require removing the carrier, you install the PowerTrax into the carrier, and most home mechanics can do this fairly easily. But a PowerTrax or NoSlip is a full locker, not a limited slip.

EDIT: Furthermore, I can't imagine anyone who has never done a gear swap being able to get the carrier shims back into place after swapping carriers. Those shims are tight and generally need a case spreader to be installed at the right preload.