Topic: Limited Slip versus Open Diff 4x4

[AP]

How big a difference does a limited slip make to an F140 4x4?  I know it is better for slippery boat launches and offroading (where a locker is even better). 

But what about onroad winter driving?  Is an open diff 4x4 a mistake?

I would pay for the limited slip but may not be able to find inventory this time of year.

[ktm525]

I am assuming the 4WD system you are looking at would be part time? ie. 4Hi/4lo/2WD. Does Ford have a version of GM's or Nissan's autotrac? If it is a part time system I would want a limited slip so you arn't constantly spinning on dry/wet pavement when going around slow speed corners etc. More traction is a good thing.

[HeliDriver]

The F150 comes standard with stability and traction control, so I assume the system would be smart enough to brake a spinning wheel to direct torque to the wheel with traction - kind of an electronic LSD.

If so, I'd be happy enough with that for everyday street use.

[AP]

The trim level that I am looking at - XLT - is only available with a part-time 4x4, which is why the limited slip is appealing.

I have read conflicting reports on the effectiveness of traction control as a substitute for the limited slip.  Most accounts reflect that traction control works simply by slowing a spinning wheel.  This will not be a substitute for the limited slip in circumstances where the differential sends nothing to the high traction tire.

[Arthur Dent]

I'd take a limited slip over traction control any day. An option worth springing for. A limited slip diff will help you in both 4wd and 2wd.

[bridgecity]

My Tundra doesn't have a limited slip diff, however there is a setting for an electronic limited slip.  Hit the traction control button once, and the traction control is disabled and the electronic lsd is engaged.  From what I can tell, the electronic lsd works the same as the traction control (using brakes), minus the throttle cutback that the traction control uses.  In other words, you can still light em up with the electronic lsd engaged with no effect on your throttle input.  

Maybe the Ford has a similar setting?

Either way, I don't know if I'd be too concerned about not having an lsd, knowing that you can engage 4wd at any time.

[initial_D]

Have both in my vehicles, for street sriving, the elctronic lsd does a very good job. On icy road, I prefer them over the mechanical LSD.

[ktm525]

Have both in my vehicles, for street sriving, the elctronic lsd does a very good job. On icy road, I prefer them over the mechanical LSD.

What about both though? I would assume a lsd equipped F150 would still have stability/traction control?

[HeliDriver]

The trim level that I am looking at - XLT - is only available with a part-time 4x4, which is why the limited slip is appealing.

I have read conflicting reports on the effectiveness of traction control as a substitute for the limited slip.  Most accounts reflect that traction control works simply by slowing a spinning wheel.  This will not be a substitute for the limited slip in circumstances where the differential sends nothing to the high traction tire.

That's pretty much how an electronic LSD works: the act of slowing the spinning wheel automatically sends torque across the open differential to the wheel with traction.

There isn't much detailed info on Ford's website about their Advancetrac system, but I did find this: "When the system detects a loss of traction, this quickly responds by reducing engine power when necessary and selectively applying brake force to the slipping wheel while transferring power to the opposite wheel. " http://media.ford.com/article_display.cfm?article_id=20679

If it works half as well as GM's Stabilitrak (which I expect it does), I think you'll never miss the LSD unless you plan on rock crawling or mud bogging.

Of course, if availability isn't an issue, it wouldn't hurt to get the LSD as well.

[AP]

Have both in my vehicles, for street sriving, the elctronic lsd does a very good job. On icy road, I prefer them over the mechanical LSD.

What about both though? I would assume a lsd equipped F150 would still have stability/traction control?

Yes, lsd supplements rather than replaces stability/traction control on F150s.

From what HeliDriver has helpfully described it sounds as though the advancetrac system (call it "LSD light") will go some distance in achieving an LSD effect.

[PJungnitsch]

There was someone else here with a 2WD Tundra and they were saying the e-locker was very effective in winter.

[ktm525]

For donuts in the winter the lsd would be desireable. Once the driver turns of the traction control it is nice to have a little more traction for maximum fun. Pickup trucks with one wheel spinning have a hard time gaining enough speed for serious winter hooning.

[AP]

So apparently the F150 traction control does indeed replicate an lsd:

http://www.youtube.com/watch?v=3on27AINjaM

http://www.youtube.com/watch?v=zrdcC7WyvG8

In fact, I understand that the availability of lsd for 2012 F150s has been substantially reduced.

[ktm525]

No fun. My last Dakotas was a perfect winter set up.

AWD:
-open center diff allowing power to the wheels that slip
-rear had a limited slip
-front diff was open

For donuts or quick turn arounds all I had to do was mash the gas and the truck would pivot. The open transfer would apply all the power to the slipping rear and the lsd would distribute. Then I would reduce throttle and the fronts would begin to bite as the rears settled down. So simple and very predictable and flickable.

Now days with TC on: Mash gas and nothing happens. Turn TC off and the rear axle is left spining one wheel.)

[AP]

The 2012s apparently will come with an inexpensive e-locker option.  That should work just as well for donuts I would think.

[ktm525]

The 2012s apparently will come with an inexpensive e-locker option.  That should work just as well for donuts I would think.

I doubt it as these systems all use brake modulation.  One wheel spins and the brake clamps down until it evens out with the other. With a full mechanical lsd there is full power. I guess there is only one way to test. I will put it in my calender for a 2012 F150 test drive in January.

[Sir Osis of Liver]

My 2008 Outback with the manual transmission came with a fixed 50:50 split viscous coupling centre diff and a mechanical limited slip rear end. No traction control or stability control. Pretty entertaining when the going got slippery.

The 2011 has the 5 speed autobox, a 45:55 F:R torque split, a limited slip rear end, but it does have traction and stability control. I'm wondering how it's going to handle the white stuff.

[HeliDriver]

The 2012s apparently will come with an inexpensive e-locker option.  That should work just as well for donuts I would think.

I doubt it as these systems all use brake modulation.  One wheel spins and the brake clamps down until it evens out with the other. With a full mechanical lsd there is full power. I guess there is only one way to test. I will put it in my calender for a 2012 F150 test drive in January.

Sounds like the Ford one is the real deal: http://www.plowsite.com/showthread.php?t=104446

I guess it's like the air lockers that the hardcore crowd uses, but actuated electrically.

[ktm525]

The 2012s apparently will come with an inexpensive e-locker option.  That should work just as well for donuts I would think.

I doubt it as these systems all use brake modulation.  One wheel spins and the brake clamps down until it evens out with the other. With a full mechanical lsd there is full power. I guess there is only one way to test. I will put it in my calender for a 2012 F150 test drive in January.

Sounds like the Ford one is the real deal: http://www.plowsite.com/showthread.php?t=104446

I guess it's like the air lockers that the hardcore crowd uses, but actuated electrically.

Whoops I confused "inexpensive option" with cheap. I figured cheap was the brake trick. This unit sounds familar to the GM unit.

[articsteve]

Mechanical LSDs have fallen victim to differential weight reduction and stability control systems.  E lockers are the cats ^ss when new (posi-traction), but like anything computer controlled/multi linked to speed/steering position/etc., when it breaks, it won't be worth fixing.