Damn Kyle talk about information overload but thanks. I saved it to my
files for any future reference. Great job on that posting.
=================================
Steve St.Laurent
2000 DC Dakota 4.7, CC, 4x2 (soon 330HP)
2000 Roush Mustang Stage II (awaiting the new SC)
"Those that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." -Ben Franklin
http://www.geocities.com/Yosemite/Cabin/4382/index.html
-----Original Message-----
From: owner-dakota-truck@buffnet.net
[mailto:owner-dakota-truck@buffnet.net] On Behalf Of Kyle Kozubal
Sent: Saturday, April 08, 2000 9:20 AM
To: dakota-truck@buffnet.net
Subject: DML: Re: Anti-spin differential
> What exactly is an anti-spin differential? I have one on my truck.(3.92)
Read this page to find out about the different kinds:
http://www.dodgeram.com/Ram/4x4/Lockrite.htm
Locker options:
http://pacific.telebyte.com/allanw/binder/locker.html
LIMITED-SLIP: A type of traction adding differential. Most limited-slip
differentials are either cone-type or clutch-type. Both types allow a
limited amount of interaxle slippage during cornering, and both use some
type of springs to provide a pre-load, or static load.
When one wheel is slipping, both types use the separating force generated by
the specially-designed differential pinion gears, combined with the static
load, to bypass the pinion gears and transfer a greater proportion of power
directly from the ring gear to both axle shafts.
Clutch-type limited-slip differentials have splined side gears that accept
clutch packs. The clutch packs are composed of eight to 10 friction discs.
The friction discs are either splined to the side gear or eared to fit into
the differential case. When one axle shaft is slipping, the separating force
tends to move the side gears out, compressing the clutch packs. Because some
of the clutch discs are eared and fit into the differential case, the power
flow bypasses the pinon gears; thus the differential transfers a greater
percentage of the power available at the ring gear to the slipping wheel
than would an open differential. Clutch-type limited-slip units need a
differential lubricant with a special friction modifier, or "anti-chatter"
additive.
Cone-type limited-slip differentials also use static load as well as side
gear separating force to increase the outward force on the side gears and
essentially bypass the pinions. Instead of clutch plates, a cone-type
limited-slip uses the side gear force to push cones splined to the side
gears into mated machined surfaces inside the differential case.
A third type of limited slip differential is the True-Trac from Tractech.
The True-Trac has no springs to provide a static load and uses friction
between the differential case and its parallel gears to transfer torque. The
True-Trac is a compound planetary gear set that functions as a limited-slip.
TRACTION-ADDING DIFFERENTIAL: A mechanical device installed inside a
differential, either a locker or a limited-slip. A traction-adding
differential is designed to combat an open differential's tendency to send
only as much power to both axle shafts as is needed to turn the shaft that
requires the least power to turn.
In order for a vehicle to go in any direction other than a straight line,
the wheels' speeds must vary from side to side. In 4x4s, this is
accomplished via two shafts per axle; one solid axle would cause both tires
to spin at the same speed. This wheelspeed differentiation happens inside
the pumpkin in, appropriately, the differential. In "open" differentials,
the driveline torque takes the path of least resistance and goes to
whichever side is easiest to turn. This is great for cornering but explains
why one tire in the air turns while the opposite one on the ground remains
motionless. So, the compromise is better on-pavement handling with little to
no tire scrub at the expense of off-road traction. Here's an overview of the
various traction-increasing differentials that are currently available.
LIMITED-SLIPS:
Limited-slip diffs (also known generically as "posis" from the
GM-trademarked Posi-Traction) offer the flexibility of allowing wheelspeed
differentiation for cornering but "connect" the axle shafts when either
side-to-side torque difference or wheelspeed exceeds a certain point. Most
LSDs use friction between the differential case and side gears to connect
the axles as opposed to lockers' meshing teeth. Generally, limited-slips are
smoother and quieter on the pavement and inflict less tire wear than lockers
because they transfer less torque per side. This is why some manufacturers
recommend their LSDs for use in front axles.
In technical terms, limited-slips' design intent is to transfer more torque
to the wheel with traction, a process called "torque biasing": the available
ring-gear torque that a given differential can transfer to one wheel when
the other one has reduced traction. Open diffs have 1:1 torque biasing; a
traction diff with a 2:1 torque bias would transfer twice as much of the
ring-gear torque to the wheel with traction as the one without.
Generally, limited-slips are one of four designs: clutch-type, cone-type,
the hybrid limited-slip/locker Eaton Gov-Lok, and planetary-type.
Clutch-type limited-slips are the most common and use spring-loaded clutch
packs between the diff case and side gears to transfer some of the ring-gear
torque to the tire with less traction. When traction loss is sensed, the
diff's clutches transfer the power to the other side by driving that side's
side gears. The spiders gears spread the side gears, which in turn exert
force on the clutch plates. Increased load increases the pressure against
the clutch plates, which transmits power to the wheel with traction.
Preload is provided by springs-the stiffer the spring/higher the load, the
less wheelspeed differentiation the limited-slip allows, making it closer to
the locker end of the traction-diff spectrum than the open-diff end.
Clutch-type limited-slips typically require a friction additive to the diff
oil for optimal operation. However, the clutches and friction area can wear
down over time.
Cone-type limited-slips are manufactured by Auburn Gear. These units use
"cones" that attach to the backside of the side gears that nest in machined
surfaces in the diff case. Under load, the side gear wedges itself to the
case. Because this design requires less force to lock the side gears to the
diff case and there aren't any clutch plates to wear out, cone-type units
typically enjoy long life.
Another limited-slip approach is Eaton's Automatic Locking Differential
("Gov-Lok"), which is a factory rearend option in many GM-built trucks. This
diff uses "governors" to detect differences in axle-shaft speed, and its
gears are activated by cam weights and friction discs when speeds differ by
approximately 100 rpm, thus sending torque to the slower side. When
"locked," the Eaton unit turns both end at the same rate, much like a
locker. However, spring-loaded flyweights keep the units from locking at
over 20 mph for safer cornering. Designed for stock applications, field
reports say that the Gov-Lok can give up the ghost on trucks that have
modified engines and oversized tires. The unit is also more costly than
other limited-slips because of its complicated design and numerous internal
parts.
Finally, the Detroit TrueTrac is a "compound planetary gear" unit that uses
dynamic loading instead of clutches or cones to transmit torque to the
unit's pinion gears. Because the TrueTrac has no springs/preload, light
brake pressure can help transfer the torque.
LOCKERS:
Lockers fall into two categories: manual and automatic. Automatic lockers
activate without driver input, transferring all of the available torque to
both wheels as soon as side-to-side wheelspeed differences cause heavy
springs to activate the locker's clutch and engage the spider assembly. The
spider assembly's teeth mesh with those on the clutch members to make both
axle shafts operate as if one solid shaft. This engaging and disengaging can
produce clunking sounds, and one side-effect is possible understeer because
only the inside wheel is driving during cornering. Increased tire wear is
another concern. However, automatic lockers are virtually maintenance-free,
enjoy proven durability, and can usually be installed by any competent
ring-and-pinion mechanic.
Manual lockers-such as the ARB Air Locker and PowerTrax Command
Locker-require the driver to engage the locker by pushing a button. This
allows open-diff steering and handling in high-traction situations but
effectively locks the axleshafts together at the push of a button in
low-traction terrain. For this reason, the respective manufacturers make
both front- and rear-end applications. Also, manual lockers are more
expensive than automatic lockers because of the actuation parts involved,
and installation is more intricate, requiring mechanical, electrical, and
even pneumatic rigging.
Finally, spools are intended for competition vehicles. Used for such things
as mud-bogging, truck pulling, and sand-dragging, spools produce the effect
of one solid axle shaft instead of two, turning both wheels at the same
speed all of the time.
The variety of traction-assisting differentials on the market strives to
provide the most power to the ground in on- and/or off-road situations.
Open differentials are the most common in cars and come standard in most
four wheel drive trucks and SUVs (Sport Utility Vehicles). 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). There are a variety of aftermarket products
that will provide a 'locking' differnetial - see lockers for more
information.
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.
Lockers
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. 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.
Lockers are manufactured by two companies. One brand is called the Lock-Rite
or L.A. Locker. The other is the Detroit Locker or No-Spin. 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 the time of writing is made by Dyneer,
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.
Hope this helps!!!!!!!!!!!
Kyle
93 Dakota 4x4 V6
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