Hey guys, new here but I need to ask a question. We have a 2011 F-450 that we use on a daily basis at work. We paid extra for the 4.88 Limited Slip axle, but only one wheel will spin. It only has 15,000 miles on it and we took it back to the dealer, but they told us that the "limited slip" now isn't like it was a few years ago. They told us that it actually didn't cause the wheels to lock and that it was basically just a regular axle. Is this correct? Does the limited slip no longer lock the wheels together if one loses traction in dirt or mud? If so, why did they charge us $360 for it? The guy in service said the rear ends didn't have any kind of clutches or anything else to change out to make it work. Anyone have any other ideas or is the guy at the service dept. just too lazy to do his job? Thanks for any and all advice.

 

Moved to the 6.7L Powerstroke Diesel forum.

While your question is not engine specific, there are several folks in this forum with F-450s and someone should be able to help you out.

 

There are many different types of Limited Slip differentials. They aren't like they used to be, where they had a fixed lock/unlock value. Most modern systems can add torque to the slipping wheel without locking up fully (which would cause the differential to bind, a potentially damaging or dangerous situation).

I don't know what the F450 uses, but if you find it doesn't work well enough for your needs, you can always get rid of it for something else. I'm sure someone makes a dedicated electronic or air locker that will work with the F-450's axles.

 

I have had issue with the limited slip in the '08 truck I had. Basically I had 1 wheel drive even in 4 wheel mode. They just don't work that great.

Somebody that knows their stuff should be able to have a look at it, add the right fluid and modifier or friction aid and get you going better.

The best thing to do is get an e locker and put it in 4 wheel drive.

 

That used to drive me nuts when I was plowing in my '08. Feel pretty foolish not being able to make it up a driveway or snowy road while one tire sits and spins

 

I have had ls diffs for years and this seems rite. What its explaned as is the wheel spins before the break away pressure is reached. One wheel dry, one wheel on ice, it will spin. The last one I had apart was 88 F250 , it had clutches. They will put power to both wheels going lets say 5 or 10 mph. Hard packed shaded snow, 25* grade, at stop , one wheel spin. 5mph, 2 wheel slip all the way up the hill and it makes it. Hopefully ELD works better.

 

My 06 F250 4x4 with a 3.73 limited slip rear end had the same issue the first winter i had it. The dealer put a new rear end in it and it has worked great ever since. The right wheel spins first then a moment later the left side kicks in.

 

I have the Factory ELD and it is great. Would almost say you can get away without 4x4 with ELD. Just don't flip while driving above 2-3 mph ....... !

 

Agreed. It is useless in my 05 as well. There is a reason Ford added the elocker now.

Too bad you can't get it on any DRW applications...yet.

Some have had success draining the rear-end oil, replacing it with new oil, and adding LESS friction modifier that recommended. The modifier makes the axle less likely to lock so using less can cause accelerated wear on the clutch. Some theorizie that Ford puts in too much from the factory intentionally to ensure that they will not have any failures during the warranty period. People of that belief took the safe route and made the limited slip useless.

You can start with that approach and if it locks up too much keep add a little more modifier until you get it dialed in.

---Aaron

 

Friction modifier - what a name. That started years ago when limited slip worked too good. Customers were complaining about the tires chirping or the axles clunking on turns.

"Friction modifier" additives work by making the lube "slippier", allowing the clutches to slip more.

"posi's" back in the 70's were just a short slip away from the lockers at the time.

Haven't checked in with the Ford yet, but the LS in my GMC did not work at all. With both rear wheels off the ground in park I could turn the wheels by hand.