I'm like you, I let the garage do the tearing apart anymore. Inside a limited slip diff there is a set of clutches that operate just like the clutch on a stick or the torq converter on an automatic transmission equiped vehicle. They allow for slipage when cornering at low wheel rpm. At high wheel rpm< meaning one wheel is turning at a much higher rpm than the other like when its spinning on a slippery surface> the clutches begin to lock up just as a clutch on a stick, etc. untill a high enough rpm is reached and they lock together just like on a stick equipped vehicles. These clutches can be worn out by over loading, too big a load, spinning at high rpm with the brake on then leting er fly, again, etc. Get the picture. A locking diff has no slipage just transferres torq to both rear wheels equally which as stated is great off road but a pain on road and leads to excessive premanture wear of driveline components. Limited slip dosen't cut the life of your drive line while lockers will if used on the street much.

 

The only way the Ford Traction-Lok will somewhat lockup is if you are putting torque to-the-ground at least somewhat on both sides.

If one is up in the air, it will NEVER do ANYTHING.

Well, at least more than 25 ft/lbs of difference, which is absolutely nothing.

If you are in slippery conditions, and have decent tires, the Ford limited-slip will lockup.

If you have crappy tires, and can't get the most-slippery one to put at least 20-30 ft/lbs into the clutches, it won't do crap.

Of course, banging the clutch or going rev/drive/rev/drive with an auto with get some lockup to occur.

I wonder, sometimes, if it's just the amount of abuse one is willing to commit before they call the tow truck?

 

There is no "lock-up RPM" on a limited slip, it is not a speed-sensitive device, it is a torque-sensitive device. However, under many conditions, increasing speed might mean increasing torque. There are clutches between the side gears and the carrier, and there is a spring preload on these clutches, so they always drag a little bit. As torque is applied, the spider gears (which drive the side gears, and hence the axles) force the side gears outward ever-so-slightly, which increases the drag on the clutches.

An example of a speed-sensitive differential would be a GM Gov-Lok, which actually has a flyweight mechanism that is driven when there is a difference in speed between the two wheels. This flyweight initiates a sequence that causes the wheels to eventually be locked together, and if I recall correctly, to remain so until the drive torque goes away. Interesting mechanism, but I have hear that they have a tendency to grenade themselves.

 

not so. i have proved that more than once in my life. the first time in 84 on a 4x4 ranger that i put in a ditch with one front wheel up in the air and one rear wheel. I thought no way but decided to try and drive it out and it came right out of there without the back wheel ever getting within six inches of the ground. Boy that incident sold me on the value of limited slip. Since that time on occasion when this discussion has come up I have proven to friends that a limited slip eqipped car will drive off of a jack if the transmission is engaged by jacking one rear wheel then blocking the axle so that one rear wheel is off the ground then driving off the block. A non limited slip diff or a limited slip with bad clutches will just sit there and spin the free wheel all day long but a limited slip properly adjusted with good clutches will drive right on off. Try it and you will see. If your limited slip won't then it is defective and in need of service. Make yourself a block slightley taller than your axle out of a 2x6 then cut a notch in one end to fit the axle. Jack er up then put the 2x6 under er and she will come right off when the transmission is engaged and the throttle depressed. If she don't, it aint limited slip.

 

Well bfloyd all I can say is you must be the chosen one. As you can see by most here, the factory LS just doesn't cut it. I had a Land Cruiser in the early 80's that I put a modified GM Gov-lok in made by Downey Off-road, worked fine. I put front and rear TDR limited slips in my 85 Toy pickup, no problems. 2001 Chevy with factory Gov-lok, no problems. This 2003 Ford would only spin one wheel when I needed it most out hunting. I took it to the dealer and they ADDED more friction modifier!!!! I new I was going to 4.30's so I saved up another $550 and had them install the Truetrac at the same time. I had these problems whether it was the factory 265's or the 285's I have now.

 

Sounds to me like you took your Ford to a bad dealer. All dealers are not equal and if you paid for limited slip and it dosen't work then the dealer, or Ford, should have fixed it. If you only took it to one dealer and didn't contact Ford when the repair wasn't done then you can't blame asnyone, thing, but yourself. Sounds to me like you wanted to put in lower gears anyway so elected to pay for an aftermarket limit slip to make the change easy. Your decision to do this in no way means that Ford limited slip is no good. All it means is that your truck may have had a defective limited slip unit that you chose not to have fixed.

 

You're comparing apples and oranges. We're in the SUPERDUTY forum. The Ranger is a "slightly" different animal.

Whether it's been the Dana 60 in my '74 highboy, the limited-slip in the 8.8"ers, or most of the Sterlings written about here, the stock Ford Traction-Lok is a joke.

It's a fact of life.

If you managed to get the 1 in 1000 that actually do anything, good for you.

But it's been talked about for 30 years that I know of.

Again, if you got a good one (on the tight side of the tolerances), that's fine. But everyone else didn't

 

First of all, everyone means everyone and I can call right now at least 20 others that have Ford SD's with LS that have had no trouble. I can't call as single person that got a defective unit out of the box although I am sure there are some.
limited slip is limited slip no matter what vehicle its in. The Ranger was an example of an extreme situation in which limited slip saved the day. I have owned three F150's and two Sd's used a couple of other that have limited slip and they have all worked flawlessly. I know many farmers with sd's with LS and several people at work own them none have ever had a problem. I guess my point is, if they are so bad how come I have never talked to anyone or known anyone that has had defective Ford LS units. I'm sure there out there but also sure that they are few and far between, at least here in the pacific northwest. Maybe Ford sends all the defective one to the area you live in?<smile>

 

bfloyd4445,

I think you are getting caught up in the semantics of the issue. It is Not that the FMC LS is "Defective" (as you put it), it is that the FMC LS system is barely better than an open differential. The FMC LS system is the least aggressive and lowest performing LS system on the market. If you need LS the FMC system will not be aggressive enough in many many situations and you will be stuck. Whereas with a better designed LS such as Truetrac etc you can keep going without being stuck. Yes in many instances a full locker is what is needed, but a full locker will not hold up to daily heavy towing on pavement, or use on icy/slick roads and thus an LS or Selective Locker (mucho expensive) is the only viable option. In this case you want the best designed, strongest and most aggressive operating locker availble. The factory GM Eaton LS is a far more aggressive system than the factory FMC system and is rebuildable with different spring pressures available to custom tune the aggressivenes of it.

Hope this helps

 

For the sake of this post we are talking about factory clutch style "LS".
I think you guys are confusing what "limited slips" actually are. The name says it all. They do not engage, or lock up with whel speed. They are always engaged. They use clutches and side pressure on the side gears to distribute torque to both rear axles. Since they are clutches, they will slip when too much resistance is applied to one axle or the other, like when making a turn. All clutch type "LS" units work under this principle. More tension on the side plates can increase the amount of bias applied, and limit the slip from each axle with a small sacrafice of on road manners during turns. "chatter" from the clutches or tire chirp can occur.
The whole driving off of the block thing is a cool way to impress your friends, but depending on the resistance of the block, even an open diff would drive off, if the diff was tricked by using the e-brake to distribute the torque to the other wheel. (Same principle as the LS unit, only using resistance on the free spinning wheel, and not tension to distrubute torque)

Some LS units are simply tighter than others, and resistance on the tires will change the manners of every LS unit differently.
Now gear type LS units are vailable aftermarket, but are an entirely different device.

 

You simply stated pretty much what I had said. I stated that after market units were better, you agreed. I talked about lockers vs. LS and you said the same as I. You stated that the factory units didn't work and I stated they seemed to work fine for me and all those I know that own them. Here is the only place we differ. My question is if they are so bad how come I and all I have talked to that own these LS units feel they work just fine? I still feel you are referring to trucks jacked up ten feet with monster truck tires on them, a use for which the factory units were never designed. My experiance is with near stock sized tires and rims. Don't you this may be the difference?

 

1) I didn't state that the factory LS didn't work, i stated that the FMC factory LS is the weakest and least aggressive LS on the market, when compared to the other manufactures factory LS that are offered. The FMC factory LS works as designed, but is not much better than an open diff.

2) If they work for you and your friends applications then great. But in my experience and many posters experience, the FMC factory LS system is a poor excuse for an LS. And yes that is in a stock wheel size and suspension configuration. For example the GM factory Eaton or Gov Lok will get you through much rougher terrain than the FMC factory LS ever thought about.

In addition the original posters question which i responded to in my original post is refering to a stock truck with factory tires. He even included pictures. I am not saying that if he had a GM factory LS he would not have gotten stuck, i cannot predict if he would or wouldn't have without testing it under the same conditions, but i will say that he would have had a better chance with the GM factory LS than with the FMC unit.

If the FMC factory LS works for you and you are happy with it then great. But for myself and a majority of the posters in this thread the factory LS is of little use. As soon as Eaton makes the Truetrac for the FMC Sterling 10.5 inch 05-07 F350 rear axle (37 spline) i will get one. For the front, only way to go is selective locker IMO.

Hope this helps

 

[QUOTE=blackhat620]1)
If the FMC factory LS works for you and you are happy with it then great. But for myself and a majority of the posters in this thread the factory LS is of little use. As soon as Eaton makes the Truetrac for the FMC Sterling 10.5 inch 05-07 F350 rear axle (37 spline) i will get one. For the front, only way to go is selective locker IMO.

Humm, sometimes these threads can get confusing. I could have confused your words. Anyway, barely works to me is the same as not working at all cause I tend to lean in the direction of a perfectionist. A pet peeve of mine is that Ford no longers sells trucks with the front LS unit. Do you have one in the front, if so which one? I would like to convert my front diff to LS.

 

bfloyd4445,

Lol, like i said its the "semantics".

No i have not installed a front locker in my 06 yet, was hoping the Detroit Truetrac would be available for the rear soon and then do both at the same time to limit down time.

When i do the front i am going with a selective locker (Detroit Electrac) as when i need it in the front i useually need a full locker and with manual hubs i can be even more selective if need be.

If i was going with a LS in the front it would be a Detroit Tructrac, as this is the best LS on the market IMO and many off road enthusiasts feel the same way. It is a gear driven unit which is far superior to any clutch type LS.
http://www.eatonperformance.com/diff...-Truetrac.html

Hope this helps

 

I think the others already said it better than I did.