All the F150s I see have LSDs. Why arent' true lockers or better yet eLockers (electronic lockers) common on the F150s?

 

it's a lib. issue, ford can't have people wrecking in the ice than blamming the locker in the rear end, for some reason no one ever sues the japan companys over things like this, but the best part was when ford was fined big bucks for letting a toyota truck hit their school bus gas tank and catching it on fire never mind the toyota was travling the wrong direction on the interstate and going 90 mph (it was fords fault) so said the jury!!! now the police are on the crown vics,after the explores rollovers, and all the other lawsuites suprised ford still wants to make a auto/truck. someplaces lsthe perferd rearend other than icy roads, like a boat ramp you take a slick (mossy) steep ramp and a locked rear end, you will be sideways (highy possible) i've seen even the best driver's have trouble and if you are in close lanes you just mite end up in the fender next to you or his/her or boat.

 

Isn't the whole point of a true locker to keep both wheels spinning equally so as to prevent walking the rig sideways?

 

I had some questions about LSD so I did a fair amount of research and even talked to tow operators (those who have some data on who they pull out of ditches on snowy days) and mechanics etc. (My own and Fords-you'd think that they would want to sell it's virtues and make the money to add it (I was asking how much) but they all said it has disadvantages annd was NOT a good thing for snow and ice and provided only limited value in fairly rare circumstances at best. (Personally I have never gotten stuck that 4 wheel engagement would not solve).



I'd get it if I had 2 wheel drive but I think those who sing LSD's praises are those who need to have everything on their trucks and view it as the best whether it REALLY is a good thing or not. For 2 wheel drive it is "four wheel drive on the cheap" for 4 wheel drive it's more of a liability. Remember now, everyone KNOWS not to slam on the brakes on ice and believes they are great drivers. Experience an accident statistics prove otherwise.

 

LS slip works well on a boat ramp pulling out over 7500lbs up a wet slippery ramp at low tide! Sorry it's not a matter of having everything installed. it just simply works. Everyone has a theory, but there is no compromise of a LS vs non LS. I have been launching boats for a very long time, and everyone who does not have a LS seems to get into a single tire burning situation, whereas those who have it just pull up the ramp! It works!

 

Is it possible to get LS installed after you bought the truck with no LS? If possible, how much do you think it'd cost?

 

In my previous Jeep, aftermarket LSDs and Lockers were common additions and were in the $175-$250+ range. Labor can be a bit expensive to install. This wasn't a task I was comfortable doing DIY. Not sure how much different the cost would be for a F150

 

if you are on a boat ramp a locker re will slid you the direction the ramp is tilted gravity goes down the same as a locked re, so in a spinning picture you would travel twice as fast towards the tilt, the reason for the straight ahead problem talked about earlier is that alot of curves on roads are not tilted and it will try and take your truck straight, even w/ truned wheels. a locked 2wd is about the same as a 4x4 w/open re but there again it depends on what type of conditions you are in sometimes the extra weight on the front wheels pulling will get a little better traction (front wheel drive cars) however a ls 4x4 is far more cap. w 3 wheels trying to do the job. one other thing about ls is that they are eaiser on axles than lockers because they will allow for slip, like if you spinning on ice and hit a dry spot, i,m not pro one or the other but there are benifits to all, it depends on your needs and what you want it to drive like. and the ls option is not just a ford issue all trucks can be ordered w/one. a limted slip will usually send about 30% of the torque to the slow wheel trying to keep it at the same speed as the spinning wheel where as a locker is just what it says both wheels will spin the same all the time even around corners, an open will only power one wheel period now it will transfere back and forth but still only one wheel will have the power.

 

LIMITED SLIP DIFFERENTIALS
The conventional differential delivers the same amount of torque to each rear wheel when both wheels have equal traction. When one wheel has less traction than the other, for example, when one wheel slips on ice, the other wheel cannot deliver torque. All turning effort goes to the slipping wheel. To provide good even traction even though one wheel is slipping, a limited slip differential is used in many vehicles. It is very similar to the standard unit but has some means of preventing wheel spin and loss of traction. The standard differential delivers maximum torque to the wheel with minimum traction. The limited slip differential delivers maximum torque to the wheel with maximum traction. Other names for a limited slip

Yes you can change to a LS, Auburn Gear makes a unit that can be installed!

http://www.auburngear.com/aftermarke...differentials/

In a standard differential, if one wheel loses traction, it will get all
the power and will spin, while the wheel with traction gets nothing. The
idea of a limited-slip differential is to prevent all power from being
applied to only one driving wheel when traction is lost. There are numerous
types of limited-slip, positraction, locker,
etc. units.

The percentage number denotes the percentage of torque applied to the
slower turning wheel from
the faster turning wheel. In a straight line, both drive wheels turn at the
same speed, so no limited slip action is occurring. In a turn, or when one
tire is spinning more than the other (such as on snow or ice), with a
limited slip differential, 25, 40, or 75 percent of the torque applied to
the faster wheel is applied to the slower wheel,
effectively 'limiting slip'. A higher lockup percentage will cause
increased rear tire wear on the inside tire during cornering -- the tire
itself will have to slip slightly to counteract the limited slip's desire
to have both tires turning at the same speed. It will also increase
oversteer in wet or slippery conditions, but it will also increase
understeer in tight corners under dry conditions. This is simply due to the
fact that with a limited slip, the drive wheels tend to want to turn at the
same speed, making the car tend to want to go in a straight line. When it
is slippery, however, both drive tires will tend to lose traction at the
same time, increasing oversteer. The
advantages are less inside wheelspin when accelerating out of a tight
corner. This also translates into more horsepower to the pavement and
faster autocross times -- provided that the suspension is tuned for the
limited slip. The ability to accelerate out of corners without excess wheel
spin can be a great advantage.


On a more technical note:

The limited slip percentage (S) is also called the locking factor. It
describes the maximum applied torque
difference between rear wheels compared with total applied torque.
Passenger car LSDs are usually in the
25-40% locking factor range. Most BMW LSDs are 25%.

Limited Slip Locking Factor or Percentage S:
(note: drive torque is torque applied to road surface)

Drive Torque Difference Between Rear Wheels
S = ------------------------------------------- x 100%
Total Drive Torque of Both Rear Wheels

Think of a situation where the two rear wheels are on different surfaces
with different coefficients of friction:

H = Higher traction, more torque can be applied to road surface
L = Lower traction, less torque can be applied to road surface

H - L
S = ------- x 100 %
H + L

By rearranging the equation a little, you see that for a 25% LSD, the High
torque side can be as much as
62.5% of the total while the Low torque side can be as little as 37.5% of
the total.

25% LSD Example:


S + 1 0.25 + 1
H = ------- = -------- = 0.625
2 2

-S + 1 -0.25 + 1
L = ------- = -------- = 0.375
2 2

The H/L ratio, called the bias ratio, is easier for me to think about
because it quickly shows how much more
torque can be sent to the high side. With a 25% limited slip, it is
possible to have 1.67 times as much torque
applied to the high side. A 40% LSD works out to a 2.33 bias ratio.

25% LSD Example:

H S + 1 0.25 + 1
--- = ------- = -------- = 1.67 (Bias Ratio)
L -S + 1 -0.25 + 1

A locked differential has a 100% locking factor (infinite bias ratio)
because all torque can be applied to one
wheel (e.g. one wheel on ice or in the air). For a limited slip, the
initial preload, or break-away torque, allows
power application when one drive wheel is on ice or in the air. Open
differentials are another story (see
snow/ice write-up below).

In theory, an open differential has 0% locking factor (1.00 bias ratio)
because the torque to each wheel is
balanced (H = L). In actual practice, there is some bias because the
differential is not friction free.

Differentials reduce tire wear and help a car turn more easily by allowing
the rear wheels to travel at different
speeds while turning corners. The inside wheel must slow down (smaller
radius turn) while the outside wheel
speeds up an equal amount (larger radius turn). To balance the drive torque
at each wheel, more torque is
applied to the outside wheel, speeding it up, while less torque is applied
to the inside wheel, allowing it to
slow down.

Open differentials always work well turning. They also apply power very
evenly when both rear wheels have
adequate traction. However, the big downside, is their torque balancing
action when one wheel has much
less traction, such as in ice and snow.

The torque applied to the wheel with the most traction can only equal the
lesser traction wheel. Total applied
torque for both wheels is only twice the traction of the worst wheel.

Increasing Locking Precentage

How do they increase the locking percentage on a diff? Do they just pack
more shims in there to make the clutch plates tighter? Or do they re
engineer the ramp angles? I have also read that Metric Mechanic adds clutch
plates. In this case is the carrier machined to accept more plates?

The shim alters pre-load, and too much pre-load provokes understeer. It'd
be better to get the locking to
almost go away under braking & corner entry, and then come back for
power-on exits. The pre-load should be just enough for a smooth transition
between the action of the coast & power ramps, and to keep things
together when unloaded. But the shim is what people can do. The shim in
question is not the 'thrust washer'
that the shop manual refers to, but the 'spacer ring' which is shaped like
a Belleville spring washer as big as
the discs themselves. These are made of stiff spring steel around 2 mm
thick. These, as well as the 'dog- eared
plates' are selected to shim up the static locking.

The torque path has the ramps driving the differential pinion's shaft, and
the ramp angle leverages the clamping force applied. Less angle on
the ramp offers a mechanical advantage for applying the clutches =
more lock. I have not measured any, but it looks as though BMW has the same
angle for both coast & power
ramps. BMW did use shallower ramp angles on euro high % LS. (Anyone want to
sell an original 75% factory
unit?)

Due to the BMW's design, the ramp angles can't be modified. The ramps are
located on the 'pressure covers'
that are also used to retain the spider gears. The back side of the gears
fits into the rounded interior section
of the left & right pressure covers. This may be so the gears assist in
their spreading action.

Adding clutches increases surface area for clamping = more lock available.
You would have to machine the
housing to fit them, so it could weaken it.

That's the facts!

 

so are you saying if you do a burn out with equal traction and tires to the truck, both wheels will smoke, i have not found this to be true and was told that an open will always favor one side or the other, just from past exper. i live on a steep gravel road and know for a fact that trying to tow a trailer up, i wouldntven be able to get started w/o a ls or locker, also i thought the ls acted like a open untill one axle started spinning fast enough to walk the cone together to try and lock the rear end thus limited still giving you open rear action on ice etc. unless really heavy on the foot. now im talking about fords ls, i know chevy and dodge did use an aurbon type of ls which was just like a clutch pack w/ springs that did the preload, you could change preload by changing the spings or cranking em down. i do know that in the sd trucks ford went with different setups depending on axle and yr my 00 350 has the one that has a herring bone type balance gear in it seems to engage alot quicker than their cone setup they used for yrs. not sure whats in the new 150's have'nt had no conditions to do hands on testing yet.

 

So in those rare instances when LSD might offer some assistance, why not just throw it into 4X4? I can see the advatage of LSD on 4X2 ("poor man's 4X4") but it seems to be mostly drawbacks on a 4X4 in terms of tire wear, fishtailing, oversteer etc. If it's true about the tire wear then that $300 option becomes far more expensive if you have to replace the tires more often......Are just the trucks with LSD having that vibration problem? Haven't had a need for it yet but here comes da New England Wintah!

 

The last truck I had was a Chevy with limited slip, and it came in handy pulling my friends bronco out of the mud that I had just driven through. He didn't make it. I live in western NY, and during the winter the limited slip helped a lot as far as I'm concerned. I didn't need 4 wheel drive very often, but would have if I didn't have the limited slip. I wouldn't have a car or truck without it, but that's just my opinion. As long as you use your head, you will keep out of trouble, and can get out of a lot bad conditions.

 

My little Ranger, with Firestone tires, wasn't very good on snow or ice. But in Austin, TX it really only happens once every few years.

I got my F-150 with limited slip. After tracking several threads about the bigger, heavier Supercab and limited slip -- my only conclusion is that I'll be just fine when it does snow. I didn't see any snow last year, I'll see what this year brings.