All I see is a number 27 under 'axle' on the door sticker. Is that the identifier?

I bought it used from a Lincoln Mercury dealer and they gave me a printed out sticker that lists under Optional Equipment:

Preferred equipment PKG.508A
3.31 RATIO REGULAR AXLE
7200# GVWR Package
Platinum Package
etc etc

 

I had a LS in my 2004 F-150 4x2. My 2009 4x2 doesn't have it, and I don't miss it, yet. I know that come this winter I'll probably be cussing under my breath for not having it. I'm wondering if the fancy-schmancy Traction Control helps were a LS would? There have been a few times where I've spun a wheel, and the TC kicked in, giving me more control.

Wonder how much it would be to add a LS to my current 3.15 rear-end?

 

I guess it depends on your use and budget. In reality a 2wd is a 1wd (one tire spinning) and a 4wd is only a 2wd (one front and one rear) when traction conditions are bad. I have not been happy with stock Ford LDS's for the last 5-6 years. I had an 02 that biased torque well. My 01,04 and 05 would one wheel on me on the street, grass, wet, mud etc... So I started replacing them with Eaton Tru-Trac LSD's. They have been the best driving diffs I have owned in 20 years. I'd swear they were lockers by the way they hold traction. I have never one wheeled with a Tru Trac. They are an all gear design with no clutches to wear or noise whatsoever...

 

Can someone give me a good explanation of just what that Taction Control is supposed to do? Is it a new name for their Limied Slip differential? My take is that if you're going to add a Limited Slip, or PosiTraction, you install it in both the rear and front differentials. Auborn Posi is the way I went on my Blazer and I love it.

 

Let me take a shot at this one. By the way, I’ve always had LS rear ends on my 4x4’s and wouldn’t order one without it – especially up here where it snows.

A Limited Slip (LS) rear is a mechanical system of clutches to limit the difference in the speed that each of the two tires on that axle spins in relation to the other. If one wheel starts to slip (starts spinning faster than the other) the system mechanically senses the difference in speeds and sends power to the other side – equalizing slip. The effect you see is two black stripes on the road. Without LS, you’ll see one stripe. A locking rear end takes this one step further and allows zero slippage between the two wheels on the same axle.

Traction Control (TC) is an electronic system that uses wheel speed sensors to detect slippage between the front and rear wheels. If it detects slip (a difference in speeds) it either applies a brake (or brakes) and / or limits power to reduce that difference. Traction control became much easier to do once we had antilock brakes because all of the mechanical parts were in place. All that was needed was some control logic. So, with TC, you get zero black stripes.

How do the systems work together? (I’ll use my truck because it has both systems.) The LS rear is on duty 100% of the time and I can’t enable or disable it. If it detects slip, it does its thing. Unless I disable it, my traction control is on full time. When it detects slippage, it starts applying brakes and / or reducing power until it’s happy. But, it might be happy because nothing is slipping, but I’m barely moving. Starting to see how they work?

Now, the traction control can be disabled though through a button on the dash. I might want to do this if I actually want some slippage such as when I’m pulling somebody out of a snow bank. When I disable the traction control in 4x4 mode, I can send power to both rear wheels (through the LS) and at least one of the front wheels. (We won’t get into locking center differentials / transfer cases here.) Then I can modulate the gas and actually pull somebody out.

Now, to confuse matters even more, Toyota now has an electronic LS rear available on their trucks. It uses the brakes to limit slip instead of adding clutches to the differential. I hear it works quite well and from a simplicity standpoint, they might be onto something. I’m not sure if the FX4 E-Locker is something similar.

 

Stroked did most of the explaining very well.

Our new Explorer has the Ford Advanced Trac system with roll stability control. I did not see any limited slip diff available. The dealer (which may be full of it) said the Advanced Trac computer programming would brake the slipping wheel and allow the one with traction to power the vehicle. We'll see as the winter gets closer. Old fashioned TC just brakes a spinning tire and reduces engine power.
http://media.ford.com/pdf/Drive_smart_existtec.pdf

An old off roader's trick when you one wheel is to click the parking brake a little to equalize the traction between the rear tires. It may help you get going some day.

 

I had a 3.73LS in my 05 and now in my 09 I have 3.55open. We just got our first big snow and really there is not that much of a difference. Sure the LS helped a little but a LS rearend is really a glorified 1 tire fire. I laid into the 09 last night and both tires spun. I guess they were slipping equally.

 

on the 09 f-150 the button does not " disable" traction control. it just resists it kicking in some.. ie it doesn't kick in as easily... only on the new raptor is there a true disengage of it..

 

Axle code 27 is open 3.31.

Ford's RSC system (and anyone else's ESC/ESP) will apply brakes to a wheel that is spinning faster than the other one on the same axle. This is often called some form of electronic LSD and is quite effective. Not quite as effective as a locker or mechanical LSD (which can use clutches or gears (torsen), but quite good considering the cost is almost free since all vehicles requite ESC soon. Brake applied LSD is not the same as Ford's E-locker on the FX4 which is a mechanical locker controlled via an electronic switch and some type of actuator.

Disabling RSC (short button press) disables engine torque limiting, but not the brake applied LSD functionality. Besides potentially overheating the brakes, there are no performance penalties to brake applied LSD. There are no reasons to disable it.

 

GREAT EXPLANATIONS GUYS !

desratt: I read that in my manual also and had to go back and verify it several times. The button DISENGAGES the TC and when you do the same symbol shows up on the odometer message display, I guess trying to tell you that your rear end will slid around more.

APT: If it's interacting with the ABS then does it work on the front axle also when you have 4x4 engaged? That would be sweet if it does.

 

It's been true for many years now that LS is best dollar value option Ford offers.

Their LS may not be the best but, for $250(?) or so you have something under there.

Deciding you want it later could run you a Grand, aftermarket.

 

That's why I can't understand anyone NOT ordering it initially. The only reason I can think is that the hype on the TCS let them believe the LS was a waste of money.

You're right on with the cost later on. It was $2,500 two years ago to have BOTH of my differentials installed with Auborn Posi units and 4.11 gears in my '87 Blazer so I'm sure the cost is going to go up.

 

I have an '09 FX4 and with the foot of snow we got this week I was finally able to see how this truck handles the snow. So far the TCS has worked great in keeping traction in the snow. I have a pretty steep hill to climb to get in to the neighborhood I live in and I went up that hill, which was covered with 3-4 inches of snow, in 2wd with no problem. I don't think my '04 Lariat with the 3.73 limited slip would have made it without putting it in 4wd.

 

I agree with Raoul, LSD is the best performance value option. I disagree that TCS is hype. I work in the ABS/TC/ESC industry. I've been to my employer's winter test facility. I've driven up 15% grade from a stop, half ice, half dry pavement in a 2WD 4dr pickup. I don't think my F-150 could have done that with LSD.

As for who would order it dealers order most trucks that end up on the dealer lots. Blame them! It's been happening for at least 20 years, well before TCS.

 

Thanks APT. I didn't mean 'hype' in a derogatory manner. Maybe I should have said 'promotion. I have a strong engineering background (35 years in the aerospace industry at KSC) and like to dig into new technology that comes out on the market. I find this 'new' TCS quite interesting. Does it also work with the front axle when the 4x4 is engaged? Does it provide a smooth braking or does it 'pump' the brakes like an ABS ?