Hello,
I have a 2004 F250 Crew fx4 with limited slip ( love the truck). I have never owned a Truck with limited slip before. Yesterday I took my truck off road for the first time.I stayed in four wheel hi. My question is : how does limited slip work? I was driving on the beach and I noticed when I hit deep sand my rpm's would go up but my speed would not increase. It felt like I was spinning tires, but I could tell the tires were getting traction and not spinning.
So I guess when the truck senses a tire start to slip it starts sending power to the one that has traction. That is why the rpms go up but speed does not increase. Am i thinking right or is something wrong?
Thanks in advence for your replies.

Brett Ferris,
Knotts Island NC

 

What you explained about limited slip is what a ford mechanic just told me. I was asking him at my local ford dealer so I could decide if I should get it on the King Ranch I am about to order.

 

There is no "traction control" on Super Duties. The limited slip, both tires drive when going in a straigh line. One "slips" when turning to prevent hop and binding like on a full posi where both tires drive all the time. The limited slip is only in the rear axel. The reason fort he RPM's going up would be the tires were slipping just a bit or the sand was softer and the engine was working harder. But there is no power to the slipping wheel on out trucks.

WELCOME TO FTE!!!!!!!!!!!

 

About the only place you will notice that a LS is working is to have one wheel on pave and the other on sand and hit the gas. The tire on the sand shouldn't spin and you should take off. The sand provides some traction for the LS to do its thing. Now ice and snow are different The loose wheel rarely gets enough traction to lock up the LS so it doesn't work well. This is all done inside the rear differential, mechanically. Even with an open diff you will get both tires to hook up if they have equal traction.
Welcome to FTE site..have fun with your truck...

Dick

 

If your driving on the beach you should air down your tires. That way you drive on top of the sand instead of trying to plow through the sand Should use 4 low too. Your truck wont have to work as hard

 

islandsaints:
Welcome to FTE! It's a great site.

An open differential allows your driveline to follow the path of least resistance; power goes to the wheel that spins the easiest. A locked differential puts all power to both rear wheels (and/or front if so equipped). A limited slip differential (LSD) is a compromise between those two. The "limited" part means that there's some attempt by the driveline (diff) to get power to both wheels, and each diff does this to varying degrees. Some LSDs are more like open diffs and others provide less tendency for the non-spinning wheel to get a free ride. Some are adjustable.

I've had friends who have welded diffs to make them "locked" and not allow any variance in the RPM of each of the front or rear wheels, depending on which diff you weld. One of these "friends" welded both his front and rear diffs, and his experience illustrates why many truck diffs are now LSDs: his turning radius on his Toyota 4X4 pickup went from 2 lanes to 2 football fields because none of the wheels were allowed to turn at different RPMs, but he could climb just about anything, at any speed. The other extreme for an open diff would be getting stuck on a flat surface when there's ice under one side of the vehicle only, and all the power goes to the wheels on the skating rink and none to those on the pavement.

And of course there are many variations on the above.

You might be able to have your diff tightened. If not, there are many aftermarket diffs that can be purchased, anywhere from a couple hundred to 1500 or more $. Each has its merits.

I hope this answers your question.

 

quick tip, if you have a limited slip and are lookin to get it to almost a locker or more traction, set the e break a little. This works great with stock tires

 

who makes a posi/truetrac rear end for the ford (sterling rear end) without going to a detroit locker?

 

who makes a posi/truetrac rear end for the ford (sterling rear end) without going to a detroit locker?

 

who makes a posi/truetrac rear end for the ford (sterling rear end) without going to a detroit locker?

 

sorry i did not mean to post 3 times

 

Sounds like normal unlocked converter slippage.

 

Differentials available for the 10.25"/10.50" Ford rear axle:

Full-Time Lockers: Detroit Locker www.trachtech.com, Powertrax LockRight (10.25 & 10.50) and NoSlip (10.50 only) www.powertrax.com.

Limited Slips: Auburn www.auburngear.com, Eaton Posi www.eaton.com, and Ford Racing Traction Lok.

Selectable Lockers: Electrac www.trachtech.com, and ARB Air Locker www.arb.com.

Auburn does also make the ECTED selectable and Eaton makes the E-Locker, but I don't see a listing for those diffs available for the 10.25" or 10.50" Ford axles. They might have something now for the 10.50, I don't know.

 

With all this discussion, I'm a bit confused now. What is everyone's recommendation for typical New England driving? What is better on the snow? And if you are plowing, is one rear end preferred over the other?

Thankyou

 

I plow with a detroit. I wouldn't have it any other way. Stock Ls's don't work in the winter. I've had most products and the detroit is almost invisible..