Just purchased an 06 Lariat with trackion control and the 3.73 limited slip. Yesterday I got stuck in the mud and only 1 wheel was spinning the other wheel on dry ground didnt move???? What the heck?

 

I've heard of newer trucks having too much friction modifier in the rearends causing the LSD to malfunction. The amount has to be just right. I'd call the dealer and discuss this with them.

 

Dang that's a hardway to find out.

 

Sounds like a limited slip to me. If one is on dry ground and the other is in mud I don't think a LS will transmit enough power to get you out. Only a locker is going to help you out in the situation.

 

Anyone know how much it would cost to swap the Ford limited slip for a locker? I have a 4x4, I would not NEED to do this on the front would I?

 

What? No. My limited slip works like it is supposed to. I don't understand why some immediately assume that the OEM LS is garbage and start looking into an aftermarket option. There have been a few LSs that have problems with the friction modifier only, me being one of them. Clearly, check with the dealer before jumping the gun.

 

I've had 3 stock Ford limited slip diffs. A 93 Ranger, a 00 Mustang GT and an 04 F150 Lariat. They have all three performed exactly as you described. The only time that they will attempt to grab is when they are cold or when they go around a turn. But if one wheel is on ice or mud they will simply not transfer enough power to the other wheel to move the vehicle, as another poster has said. I do not know if this is 'normal' , but like I say all three of these vehicles did the same thing. It does not make sense to me, but they only seem to grab when the wheels are very close to the same rpm, for instance in the GT if I break the tires loose at speed she will definately spin both wheels, and I know that the GT leaves nice dual 'burnouts', but still, only one wheel spins if she is on ice or mud. Revert to the parking brake trick for these encounters.

 

Guess I have just done too much off roading with lockers front and rear and know the difference. My LS in the f150 is a little tight it seems. The inside tire on a turns usually chirps a little but I don't mind. Haven't had mine in mud so I don't know how it would react in that situation.

 

LS only lock both wheels when they both have traction. i know this sound useless in an offroad truck but it's true. this is the case if you are on decent traction pavement/cement and hammer it, like in a powerfull car for example, it will leave two black strips. in the snow/mud, forget it. it's just a clutchpack, it will only hold so much before slipping. LS don't TRANSFER power to the other wheel, it just lets one wheel slip indepently of the other. torque sensing diffs do transfer power to the slower rotating wheel, like a Torsen for example and eaton just came out with their version, Truetrac. the torsen come factory in the HumV. they work very good for low traction situations. power transfers to the slower turning wheel, this is great for mud and snow. but the only drawback is they work on bias....so if one wheel is doing 0 rpm, the bias of 0 is 0, hense u don't go forward....but a small application of the brake, slowing the spinning wheel enough to tranfer power to the other wheel will get you moving.
and of coarse there are selectable lockers. which Auburn is currently working on the 9.75" ECTED. there are a few available for the 8.8

 

here are two tricks to get around this

1. drain the rear diff only put 4 oz of friction modifier, the 9.75 calls for 8 oz, this will cause the clutches to wear out faster and you might get alittle clutch chatter going around turns but it will work alot better offroad.

2. when you find yourself in this situation, apply the parking brake some as said ^ or you can also apply alittle brake as you give it gas at the same time.

i myself have 4 oz in my diff for around 30k miles (hard miles) and the clutches are still in good shape i only have 40K on my truck as soon as the clutches wear out i will be throwing a ARB in there front and rear. good luck.

 

ARB's have known to leak, and don't disengage instantly.

 

This is not correct. The clutches kick in the other wheel WHEN one wheel spins faster than another:

the only time the clutches step in is when something happens to make one wheel spin faster than the other, as in a turn. The clutches fight this behavior, wanting both wheels to go the same speed. If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.

http://auto.howstuffworks.com/differential1.htm

Basically with a posi, both wheels are pushing ALL the time unless the clutches are cut loose to Allow one wheel to spin faster than another (like when you make a turn). If one wheel is spinning and the other is not it means your clutches are NOT engaged or slipping (either wore out or have too much modifier on them).

When you stomp it in mud, gravel, snow, etc BOTH wheels should be spinning. The problem is people don't like the "chatter" a LS has when it turns the corners. This is normal and something LS's have. Anyway, since they don't like it they add a bunch of Friction modifier to make the clutches slip and then they wonder why their posi doesn't work.

If you have a LS, and you were stuck in the mud with one wheel spinning, you have a problem as this is not normal.

 

I have an appointment next week with the dealership to check fluids, and hopefully drain them, as I have had a similar problem on the snow and ice. Hopefully it is just too much modifier and it'll be taken care of. I'll let you know.

 

And sometimes the buildsheet says LS and an open diff axle is installed on the assembly line.. Hope that's not the case for you but it happens.

 

Yeah, press emengrey brake pad a little (2 or 4 click), it works for me.

ARBs, true unless if you have best 4x4 repution install job then no leak. Call ARB and ask for best installer in your local if you want ARB.

YOMAN!