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Got a friend that has a 2011 crew cab dually and the limited slip sucks. It spins one rear tire in the mud or snow?? That normal?? It also spins only one front tire too when in 4x4 with the hubs locked?? Do they make a Electronic locker for the front and rear?? Also are the axles a dana 60? 80?

Derek
 

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He may not have limited slip. If so, some slipage still occurs. No locker or limited slip in the front from Ford.
 

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The Limited slip in these trucks suck. I have one in my 06. The dealer told me they work like a open differential and don't tranfer power because they aren't a locking rear. I then asked them why they call them a limited slip? No real answer. The only way to maybe get it to work somewhat well is to drain the fluid and put non-limited slip fluid back in. Drive it on the road and see if you get any chatter.

If not that is the best it is going to get.

If it does, then add 1 oz of frictoin modifer at a time until the chatter goes away. I only had to add 1 oz in mine when I did it.

If you want to fix it right get an Eaton Trutrac. I just don't have the money yet.
 

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Don't know about you guys, but I have a F350 with the e locker and all 4 wheels grip. I just pulled out a tree stump and I left 4 skid marks on the asphalt when I accelerated it to much.
 

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What is Ford's definition of "limited slip"? Is there a Ford rep on this site who can explain it to me? I love this truck (2011 f-350 cc) but I need to know what "normal" is. I have the very slightest incline (one inch of rise over 4 feet of travel) in my driveway. The other day I had one tire on bare asphalt where the sun hits the driveway, and the other rear tire was on ice (in the shade). Immediately upon putting it in drive the right tire started to spin and the left tire sat there. I had to shift into 4WD to move forward. Thanks!
 

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Limited slip is just that, a limited amount of torque before it slips. If both tires are on a similar surface, both will spin. If you have say ice or mud under one and dry dirt of pavement under the other and exceed the torque limit, only one tire spins.

I know on littler trucks it was 150 ftlb to slip the LS rear axle.

elockers, detriot lockers any other locker does just that, locks them together. The axle would break before they slip.

There is just a set of clutchs on a LS rear end on each side gear, they normally have a spring that applies tension to help them hold. The work great for what they are designed to do.

A detriot locker only unlocks to let one tire out speed the slower inside tire in a corner. It's easy to spin the inner tire that way.

If a LS was set up too tight it would also slip the tires in a corner, which is bad for many reasons.

elockers are the best of everything, my drw doesn't have on offered.
 

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Thanks for the quick response and excellent explanation.
To add to what Diesel Dr. said, in your example, if you would have clicked on your emergency brake about 3-4 clicks, that would have kept the tire on the ice from slipping, and transfered more torque to the tire with good traction and you could have drove right up your drive without engaging 4WD.

The FMC owner's manuals used to describe that technique but don't think they do anymore.
 

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Dr Evil is right. When you apply load to the diff, the side gears push out on the clutches which makes them apply harder. Play with it a bit and you can get amazing grip out of it. You HAVE TO maintain torque load though or the clutches will go back to their normal mode.
 

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In my case, a quick tug on the 4x4 shifter would've locked them in. Of course 4x4 would have worked too. I've been there done that with one tire on wet grass the other on pavement. Both methods worked for me.
 

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When you apply parking brakes you are not loading the clutches. The D80 LS unit is loaded by springs continuously but not with so much force for reasons already mentioned. You are loading (braking) the wheel with low grip that would readily allow the torque shift to that "loose side" because it is enough torque to slip the axle gear clutch on that side. You are of course loading the tractive wheel too but in this situation that doesn't really matter.
The brake drag method works on open diff vehicles too. The park brake drag method has limits.
The brake apply traction aid that so many vehicles use now is doing this same task but it applies the single brake on the slipping and over-accelerated wheel as measured by wheel speed sensors.
 

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Limited slip units are but one of a large variety of traction control aids.

In the 2011, I believe the OP has a limited slip device that is based upon clutch plates and friction discs; this is a very common design because it's effective (for a while) and it's inexpensive to manufacture.

This type system uses constant force spring(s) to put pressure on the clutch/disc assy to brake the low-traction side. This effect is called "torque bias" and often traction aids are rated by their "bias". Lower numbers indicate less ability to transfer torque; higher = more transfer. Really high bias makes for great dual traction, but can also be a PITA on the road with lots of wheel scrubbing and clutch chatter at times. This type system also wears down; the friction material will wear off over time. This wear effect is dependent upon amount of mileage, severity of turns under high loads, etc, etc.

The upside is that these are generally inexpensive to repair (parts are cheap, labor may not be), and they are "tuneable" for a lack of a better term. LSDs can be upgraded with more agressive springs and higher CoF (coefficient of friction) discs. A Ford dealer is going to only know one answer; stock MC parts. That's not a bad thing, but it does not address other concerns if you want to "tune" the bias to a more aggressive state. Aftermarket places offer alternatives.

Aftermarket options also offer many other forms of traction control, such as true "locker" (dog/ratchet type) units, gear driven (helical), metal clutch (cone type), and such. These categories can even be seen sub-divided into smaller groups. For example, "lockers" can be full-time (No-Spin) or part-time (E-locker or Air-Locker). And so forth ...

The reality is that the Ford L/S units are "average" at best when new, and as they age they wear to a point where not much bias is present any longer; they almost act as an open diff would. You have a large aftermarket of options; investigate and make a choice.


Hope that helps.
 

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Thanks for all the feedback, folks. Your explanations were excellent and your advice was practical. Best regards to you all!
 

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you can add more of the limited slip additive to make it bite more. Well maybe I have it backwards not sure. Anyway you can change the amount of the additive and make the rear work or engage better but it will also reduce the clutch packs some. However I will take a working unit any day. I have the Eaton lockers and they work great. Eaton also makes a great limited slip that actually works.
 

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Would have to agree with dneuton calling the ford unit average, got the electronic lock on my truck and have been stuck many times and ALWAYS had to use 4wd to get out. This was true for mud, snow, or ice. My 04 truck was the same. Guess I do not understand where this is suspost to work.
 

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Gm actually offer the best and most positive rear tractor system. It works as good as fords rear locker but it totally automatic and instant. Fords limited slips are junk and when I buy a new truck i quickly put in after market. For alot of highway driving i like the following.

Eaton limited slip
Eaton electronic locker
Detroit true trac.
 
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