Hi-

Just saw these LS differentials and they are half the price of an Eaton Posi unit. From what I have heard, the Ford Motorsport (Auburn units) HD differentials are a lot stronger than the Eatons.
I'm thinking that this would be a nice mod. since I'm roasting up the one tire all the time.

Anyone have the FMS Auburn HD differential?
Whay are your experiences?

Thanks.

 

If L/S is about half the price of an Eaton; then it is probably OEM Tracloc (part# M4204F318, for an 8.8") or an aftermarket U.S. Gear.

Auburn makes (2) different L/S's. Auburn PRO and Auburn Heavy Duty. Auburn PRO will be priced at little bit higher than an Eaton-Posi. Auburn Heavy-Duty is usually a little less $$$ than Eaton Posi.

Eaton and both Auburn units are good. Auburn Pro being top of the line. Eaton-Posi gives you a little better advantage for the $$$ savings. Auburn Heavy-Duty: much better than OEM trac-loc.

I own both Auburn Pro and Eaton-Posi. For deep snow driving, I like the Auburn Pro best (it is not as aggresive to the feel of the seat of your pants). For Mud driving, I like the Eaton-Posi (it seems more aggressive and macho).

If I could purchase a L/S for half the price, I would be very cautious because it would probably be like comparing a piper cub to a F-17 Stealth fighter.

 

Thanks for your detailed reply. The Auburn unit is the OEM Heavy Duty application, which is about $300. at Ford. The Eaton is $200. more. They also have the Tracloc which is less than the Auburn HD unit. I didn't see the Auburn Pro, but I would be interested.

I'm looking for strenght and performance. Would the Auburn Pro be the best way to go? Or is the Auburn Heavy Duty stronger?

You guessed it, I have the 8.8 rear-end.

 

Ford Motorsport differential is OEM trac-loc (jegs part# 397-M-4204F318). I don't know who produces it for FOMOCO, or if Ford manufactures it in house. OEM trac-loc is not heavy-duty.

For a tough L/S: Auburn Pro or Eaton-Posi. For tough L/S (on a budget): Auburn Performance (also known as Auburn Heavy-Duty).

Jeg's website pricing on 8.8" L/S for 31-spline:
Eaton-Posi: $462.99
Auburn Pro: $414.99
Auburn Performance: $339.99
OEM FOMOCO Trac-loc: $259.99 (u.S. funds)

You might want to view these websites for more info.:
http://auburngear.com/
http://www.lightruck.com

 

The Traction-Lock is a great diff and is what I'd get. It is cheap (I paid $200 wholesale for my last one). It is rebuildable. Auburn is not. The Ford Tracktion-Lock can have the clutches restacked so that it locks up as tight as an Auburn Pro. You do need to buy a clutch rebuild kit (about $50). Look at www.corral.net technical articles for the rebuild/restack of the 8.8 Traction-Lock. Mustang guys put 500 HP on slicks thru these with no problems.

 

Trac-loc comes stock on a Mach 1 Mustang (dual overhead cams 4.6L) with a 3:55 rear ratio. I was drooling over one today.

 

I can speak for the Eaton Posi unit. It is an excellent all around rear. The clutches are designed to withstand racing and it is rebuild-able though I doubt it will wear out with normal use and good maintenance. I went from a true locker (very uncomfortable) to this rear and did so because of its reputation for dependability, locking ability and comfort. Sometimes true performance comes at the expense of comfort. Not so with this rear...

 

Bent6 is right, that's what I was saying on another post about this same subject. Being a Mustang head (I have 3) I apply all I know from stangs to my truck. The trac-lok is the bargain unit and if you stuff 1 or 2 extra clutches in there it hooks great and when it starts to crap out, you rebuild it. Remember, these other units were designed primarily for drag racing, a car that sees the track maybe twice a week. You can use them on the street, but they wear out sooner. Why spend $400 bucks for something you have to replace when it is done??? In defense of the Eaton, it too is rebuildable, but I know the parts are more costly than the Ford stuff.

Besides, if you are willing to spend over $400 for a diff, then get the best, a Zexel Torsen diff, the badest, no clutches, no cones, nothing to wear out and can handle anything you can throw at it.

 

Fast Pony,
Most on this board do not have the experience to do a clutch switch or to add clutch discs to the rear. When I did my rear for the second time I was really considering the Zexel Torsen diff but no one, and I mean NO ONE had enough experience with it to be able to recommend it for truck applications. It does sound like the ideal rear...

 

Hey WLF,

That's cool and I understand. Even with all my years of rebuilding and modifying my Mustangs, there are still things I leave to the pros, and setting up rear ends is one of them. If improperly installed and setup, they will self destruct in no time. Any good shop that does rears can add the clutches no problem, even if you want to do the final install yourself.

As far as the Torsen diffs, the only possible draw back is slightly more heat generation. Transfer of power is through a set of planetary and worm gears, hence no clutches or cones to wear out. Running synthetic would pretty much eliminate the heat issue. Many of the world’s finest sports cars that make serious power use the Torsen diffs, so I can't imagine most trucks would even make it sweat. It was designed to be abused.

Anyway, just my two cents worth.

 

Just an update:

I will no longer be a F-150 driver as of 4:30pm..PST.

I will have a 03 Mustang GT!!! I will have to see what LS is in there. I know it has a 3.27 LS RE.