The clutch pack in a LSD does need to be replaced every few years. The clutch plates slip (wear) whenever the truck does tight turns on pavement. Once the clutch packs in a limited slip differential wear out it turns into an open differential.

That could be the case on your '04 Lariat.

 

Yeah. My clutch packs went to crap on my '04. It would shake every time I turned a corner from a stop. $900 to replace them.

 

I agree -

This is my first F-150 with TSC - the rest had LSD -

With our first snow, I was pulling out into an intersection uphill with snow/slush cover. All my other F-150's with LSD would have spun both wheels, and also side-slipped. I would have had to let off the throttle to control the wheel spin and fish-tailing.

With the TSC, I was pleasantly surprised in how well it worked in this situation - I felt the engine bog a little, but no more than if I had to feather the throttle myself to get going. The truck pulled straight out (no fish tailing) just fine - I am impressed and glad I have it now!

 

Even if his 04 did have worn clucth plates then the fx4 and 04 lariat would have both functioned as an open diff. Remember the fx4 only has a locking diff and not a LSD. So it's always open unless locked.

 

REAL,

Where the 'H' did you ever hear that clutch packs in Limited Slip differentials had to be replaced every few years ??? That's absurb ! I had a LS in my '92 and put 270,000 miles on it in the past 17 years and NEVER had a problem and it was working absolutely fine when I traded it in a week ago. Maybe if someone let all the lube drain out or put the wrong lube in the differential then they would burn out.

 

Driveing like a batt out of hell can wear them. Dpends on how easy you take it with using them. Just like a clucth they can wear out quickly if over heated.

 

Well, you're sure right on that Barritia
I guess I made a bad assumption that everybody drives their vehicles with a little common sense and maintains them properly. I find it amazing that someone can take a $40 - $50,000 truck out and just beat the hell out of it and then wonder why it's falling apart. Hard core 'off roaders' don't drive run-of-the-mill vehicles. They are specifically built for the application and don't reflect a stock showroom truck and they expect things to break.

I drove my truck as a daily driver, took some long trips with and the only off roading was really just out in the pastures on a local ranch. After 17 years and 270,000 miles this what it looked like the day I traded it a week ago;

 

I cannot speak for the F-150's system, but generally, yes it would work for both axles.

The system pulses the brakes similar to ABS The difference is that the system has to build the brake pressure vs. the driver for ABS. Once enough pressure is built to lock a wheel, the system pulse it exactly like ABS.

My LSD clutches were worn (vibration while turning + accelerating) around 30k miles on my current F-150. You don't have to drive crazy to engage them. Turning out into traffic, lots of snow/ice, etc.

 

The LSD's take a different lubricant and usually require an additive to improve friction of the clutches. My Auburn Posi unit installation instructions specifically had a warning note to do that. I suspect maybe someone put in the wrong lube somewhere along the line. I spec'd out my '92 new with a LS and it showed up without it. Before I took delivery I made them put one in so they pulled one out of a vehicle in stock and tried to stick it right in. I made the mechanic clean out all the original lube and replace it correctly so hence I got 270,000 miles out of it with no problems, and in those miles I made a LOT of turns :-)

 

No need to be a jerk about it. LSD clutch pack wear is just a fact of life. When clutches slip, they wear. It's not necessary to abuse the truck to cause this wear because the clutch is designed to slip in normal use. If you don't need a LSD then there is no need to replace the clutch pack when it wears out, it will simply function as an open differential and that is what your truck with 270,000 miles on it was probably doing.

 

It's not just turning. It's turning while accelerating (moderately to aggressively).

 

While what you say IS true, it isn't the complete story. Yes the clutch pack in there does burn off some material, but it is extremely small amounts. Much, much less than a normal clutch which also has less material and is expected to last many, many miles.

200k miles might be an extreme amount on the high side, but realistically 30k on the low is also EXTREMELY short for an lsd.

As for it getting stuck open when the material runs out, that is also incorrect. The clutch plates would touch, causing for loud banging as metal on metal provides inconsistent friction, eventually causing who knows what kind of a situation. On the other hand, banging, grabbing or other symptoms can be caused by inadequate/wrong/contaminated LS compound in the diff fluid. In fact that is a common issue in some high power situations, where the diff can be under extreme stress for long time periods (racing).

In a truck with a large (comparatively) diff there is a huge amount of friction material and very low level of consistent stress. If your lsd failed in say under 150k miles, I would rate that up as a part failure and not part of the design. Unless of course you let the fluid run low, it was contaminated or something else happened.

 

REAL, I'm not trying to be a 'jerk' but c'mon, every few years? You think Ford could ever sell anyone into have them installed if they knew part of their routine maintenance was going to be to pull the differential apart and rebuild it every couple of years? I had mine checked during my last service and it was working fine, but then I basically drive the truck as a 'car'/daily driver and never had to deal with northern winter climate conditions, just wet Fla roads, and never did any hard Off-Roading with it (to pretty of a looking truck to do that ha ha). It wasn't a 4x4, I just wanted the LS in case I needed to pull a boat up a slipery boat ramp, which is pretty much the main reason for a LS or 4x4 here in Fla.

Well ....except ..... naw, I'm not going to even address the swamp/mud buggy races they have in Naples every year ha ha ha.

That's OK , we may have different opinions and/or philosophies on that but we can still respect each other's opinions ;-) We can leave it that I just got 'lucky' or they built them better back in '92. PEACE !

 

If it is grabbing and chattering in turns then it is working too well. That sound is the clutches trying to keep both tires connected in a turn. The Limited slip additive is a slip agent that reduces the friction and clutch grip. Only run as much additive as needed to smooth driving. Any more will further reduce the friction of the clutches. Most all cars use synthetic fluids which are rated for LDS's etc now days. The additive is only needed with dino based oils and to solve clutch chatter when it is undesired. I had an Auburn Pro Series in a Chevy and it would chirp the tires when turning on assphalt or wet roads, I loved it. That told me is was biting nice and hard inside. I eventually added friction modifier to make it slippery enough that it turned quietly.