> This is my first 4x4 and I need to be a little more educated on how this
> thing is working when I'm off-roading. I've got a '01 4x4 (part-time,
> dial on the dash) 5spd w/LSD. Here are a couple of questions.
>
> When you are in 4 wheel drive, how does the truck determine which wheel
> of an axle get's the power? Does a truck with LSD do something
> different that a truck without LSD when it trying to get traction?
>
> Who can tell me more about 'lockers'? From what I understand this is a
> mod to 'lock' the axle so that both wheels of the axle are always
> getting power, is this correct? Does this require a new transfer case
> or do you just add a new part? Is this expensive? hard to DIY? are
> there any reasons why I wouldn't want to do this?
Vic,
So Dodge really is usings a 4WD activated 'dial on the dash and no more
lever?????!!!!! Grrrr, why would Dodge do this!? Oh well, looks like I can
stop looking at the 2001 models! Seriously though, when upgrading to or when
using a rear LSD or locker, no mods need to be done to the transfer case. It
really is a 4WD KNOB!? I still cant get over that. Oh well. Lets move on.
Open differentials are the most common in cars and come standard in most
four wheel drive trucks and SUVs. The open differential is a system of gears
that keeps the same amount of pressure on the faces of the gears that drive
each of the axle shafts (to the wheels). When one wheel turns faster than
the other, as when turning a corner, the pressure on it is kept up (so more
power is applied to the faster turning side). This is the best possible
application of power on smooth dry surfaces and provides the best handling.
In poor traction conditions, as in sand or mud, this is the worst possible
application of power. When one of the wheels has no traction, it spins.
Since the pressure is kept the same on both axle shafts, little or no torque
is available on the side that is not spinning (and which may have traction).
A typical open differential will keep the AVERAGE rpm of both axles constant
relative to the drive shaft rpm. For example, when one wheel is not turning
(0rpm), the other wheel will be turning at 2 times the rpm that it would be
if both wheels were at the same rpm - relative to the drive shaft. This
behavior is due to the spider gears and therefore will also be present in a
limited slip design which uses the spider gears. In a non-wheel-slip turn, a
open diff will have the outside wheel faster than in a straight line and the
inside wheel slower than in a straight line for a constant vehicle speed. In
a locker design which does not use spider gears, at least one wheel must
turn the same (relative) rpm as the drive shaft while the other wheel can
turn faster (but not slower). The opposite of the open differential is the
spool. The spool replaces a differential with, effectively, a solid axle
shaft between both wheels. The right and left wheel must then move at
exactly the same rate. To turn a corner, one or both of the wheels must slip
on the ground. This places an enormous load on the axle shafts and wears
tires rapidly, if it is driven on dry pavement. To completely lose traction,
both wheels must lose traction and spin. Spools are often used on off-road
racing vehicles. A number of compromises between these two extremes are
available. These are: differentials that can be switched manually between
spools and open differentials, lockers, gear driven limited slip
differentials, and clutch driven limited slip differentials. Each of these
has advantages and disadvantages. There are two sorts of manually actuated
locking differentials. One is operated by air pressure. A compressor is
installed and a solenoid is controlled by a switch operated by the driver.
Pushing the switch connects the compressed air source and pushes a piston
that moves a ring that locks the differential. When the switch is pushed
again, the line to the differential is vented and a spring returns the
differential to its normal, open condition. This system is marketed under
the name ARB Air Locker and is available for a number of common axles. Not
sure if ARB is a 100% bolt on for Dakotas. I think they use a Dana 30/35
Hybrid upfront and a 9.25 in the rear. Check around 4x4 websites, especially
http://www.ring-pinion.com . Reliability is the main drawback to this
system. Sticking of the solenoid or leaking of the air tubing are the main
causes of failure. These problems are easily repaired in the field. A
blow-out in the seal within the compressor or the piston inside of the
differential are not so easily repaired, but are much less common. Some
people object to the cycling of the air compressor, both when in use and
when in standby. This is the most expensive type of differential, really
really pricey. Lockers are manufactured by many companies now awadays, some
being called Lock-Rite and Detroit Locker. These are similar in use, but
differ in application (what they fit) and in internal details. Both of these
act very similar. When driving in a straight line the locker is normally
locked. On dry pavement, when cornering, the outer wheel over-running the
speed of the axle unlocks the outside axle shaft. Power is applied to the
inside wheel only. This can cause a noticeable under-steer. Additionally, if
enough power is applied while in the turn, the axle will lock up and the
vehicle either slips wildly, spins or straightens out suddenly. These
differentials sometimes make a clicking noise when cornering; some find this
objectionable. This type of differential is not suitable for front axle use
in vehicles with disconnect axles in the front. Disconnect axles are used on
the front end of some newer vehicles. They are considered by some a nice
feature and by others a terrible fault. They are used with "shift on the
fly" four wheel drive. The problems with using lockers with such axles are
that the drive shaft will be driven and that the side not split by the
disconnect will undergo drag, especially when the differential is cold. This
will cause a pull toward the side of the front axle that the differential is
on. Limited slip differentials of both gear and clutch types will transfer
only a fraction of the available torque to the side that is not slipping.
This is not as good as a locker, but may be enough to get you through. Many
vehicles are available with limited slip differentials as a factory option.
Limited slip differentials are not suitable for use in the front axle of a
vehicle with an axle disconnect. The only gear type limited slip at this
time I think is from the company that makes the Detroit Locker. It works by
having the speed difference between the wheels wedge one of the gears in a
pocket, reducing the freedom of movement of that side. This transfers torque
to the other wheel as long as the speed difference is large enough to keep
the gear in the pocket. This type of differential requires no special
service and no special lubricants. The main drawback to this approach is
mechanical weakness. The True-Trak is available only for lighter vehicles
and is recommended only for light or medium duty off-road use. The clutch
type limited slip differential is the most common traction enhancing device.
It is the cheapest, but also the least capable. It uses a clutch or clutch
pack to couple the axle shafts when the speed becomes too different between
the two sides. The clutch does not transmit all the available torque when
new and becomes less effective with time, eventually becoming effectively an
open differential. The clutch must be replaced periodically. Special
lubricants must be used in these differentials to increase the friction on
the clutch. All of these enhancements have drawbacks. The most expensive
ones have the least serious drawbacks (excepting price). They can be a big
step up from an open differential. None of them will always guarantee
traction, since all four tires can be spun at once! Preventing a wheel from
spinning not only reduces the chances of getting stuck and increases your
chance of pulling a hill, it also reduces the chance of breaking equipment
when an airborne, spinning wheel hits the ground. Preventing a wheel from
spinning is also a big part of treading lightly. A spinning wheel can move
alot of soil leading to ruts, erosion, and dust.
Sorry is this is LONG, but copy and paste works so great and I think the
above information is excellent, for use 4WD gear heads atleast. Hope this
helps and good luck.
Kyle..............Real Dakotas Are Built, Not Bought
http://www.bastaards.org/Preacher/Dakota/DakFriends/dakfriends.html
93 Dakota; Emerald Green; Sport Regular Cab 4x4 V6; 3.55 LSD
MSD 6-Offroad Ignition, MSD RFI Noise Filter, MSD Universal Wiring
Harness, MSD 8.5MM SuperConductors, Accel Super Coil, Borg Warner
Select Brass Cap/Rotor, Autolite Copper Plugs(.050), QuickD Throttle Body,
Ford Motorsport #19lb/hr Matched Injectors, 'PoBoy' Homebrew Cold Air
Intake Kit Using GenIII Dak Air Hat, K&N #RE-0920 Cone Filter(900+ CFM),
K&N Breather Filter(PN#62-1520; All Metal), Flowmaster 3Chamber Delta-Flow
Muffler
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