Are you ready to take your BMW to
the next step in drive train performance? Wavetrac has
finally released their Automatic Torque Biasing Differential
(ATB) for the E39 540i. The OEM differential was never
designed for high horsepower out put or track use. This
ATB Wavetrac diff was specially designed to handle as much
horsepower as the 4.4L V8 engine can put out, and is guaranteed
to last longer then your vehicle. The OEM differential is
an open diff, where one wheel is able to spin freely if it is
lifted off the ground, giving the other wheel absolutely no
power to the ground. Wavetrac has patented their one of a
kind design that is able to keep the power to the ground no
matter what kind of situation it faces. Be the first to
have the latest drive train technology in your BMW with the
Automatic Torque Biasing
NOTE: Ring gears are welded to the differential on
the 1 and 3 series vehicles made after March of 2007. This means
you will have to purchase a new ring gear from BMW to use with
the Wavetrac diff or have an installer take the ring gear off
your BMW diff and use it with the Wavetrac. Also BMW does not
sell the bearings for the Differential separately. Please Use
caution or the correct tools while removing the bearings. This
has only been confirmed for the 540i, call your local dealer to
check on bearing availability.
Wavetrac At A Glance:
pending Wavetrac design automatically improves grip in low
traction conditions. This feature is truly innovative and
unlike any other torque biasing diff design.
9310 steel gears run in case-hardened billet steel
bodies. ARP fasteners used throughout.
As supplied new, the Wavetrac differential will perform a
lifetime of service without maintenance or rebuilds.
desired, you can alter the diff’s behavior to suit your
needs using optional components.
Limited LIFETIME Warranty:
All Wavetrac differentials include a
transferable, Limited Lifetime Warranty.
What makes a Wavetrac Different?
understand how the Wavetrac is truly different from the other
gear differentials on the market, you first have to understand
the primary problem that the Wavetrac
problem: Loss of drive during zero or
near-zero axle-load conditions.
Zero axle-load is
a condition that occurs during normal driving, but creates the
most noticeable problems when driving in extreme conditions.
Zero or near-zero axle-load is the condition that exists when
there is ‘no-load’ applied through the drive train, when one
drive wheel is nearly or completely lifted (often in aggressive
cornering). It also occurs during the transition from engine
driving a vehicle to engine braking and back, even with both
drive wheels firmly on the ground.
Here’s how that loss of drive hurts you:
1) If you lift a wheel, all
gear diffs except Wavetrac, will NOT power the other wheel.
2) During the transition from
accel to decel, all gear diffs except Wavetrac, do nothing.
Why does this happen?
All gear LSDs
(including Torsen, Truetrac, Quaife, Peloquin, OBX, etc.) work
in basically the same manner: they divide the drive torque
between the two axles, applying drive to each side, up to the
available grip of each tire. The amount of drive torque one
wheel can get over the other is described as the
bias ratio, a measure of the torque split across
differentials have a bias ratio of 1:1. They can only apply as
much drive torque as there is available traction at one wheel.
When one wheel loses grip, the total available drive is lost as
well (at a 1:1 ratio). All your power goes out the slipping
wheel - along the path of least resistance.
differentials offer increased bias ratios over open
differentials. For example, if a diff has a bias ratio of 2.5:1,
then it can apply drive torque to the wheel with the most
traction (gripping wheel) at 2.5 times the traction limit of the
wheel with the least traction (slipping wheel). This is a
significant improvement over an open diff… most of the time.
The problem is
that when one tire has LITTLE or NO
grip (zero axle-load), the other wheel gets ZERO DRIVE,
because (basic math here): 2.5 x 0 = 0.
Lift a wheel (or
substantially unload a wheel) and you get zero axle-load on that
side - that means that during the time the wheel is unloaded,
the typical diff will NOT power the wheel
that’s still on the ground. No matter how high the bias ratio,
you get no power to the ground.
transition from accel to decel, where you have near zero torque
on the axle, even if the wheels are on the ground, the typical
diff is unable to begin applying drive torque until AFTER the
zero torque condition is over. While this condition is generally
short-lived, the fact that most diffs can do nothing during that
time means that there will be a delay once the zero torque
condition stops - creating a reaction time in the driveline.
The Wavetrac, however, is different:
patent-pending, Wavetrac device in the center of the diff
responds during these exact conditions when zero or near-zero
axle-load occurs. At or near zero axle-load, the axles (and
therefore each side gear in the diff) start to turn at different
speeds. This speed differential causes the Wavetrac device to
step into action:
engineered wave profiles are placed on one side gear and its
mating preload hub. As the two side gears rotate relative to
each other, each wave surface climbs the other, causing them to
this creates enough internal load within the Wavetrac to
STOP the zero axle-load condition.
axle-load condition is halted, and the drive torque is applied
to the wheel on the ground (the gripping wheel)… keeping the
differentials rely solely on preload springs to combat loss of
drive. The drawback is that you can’t add enough preload to
prevent loss of drive without creating tremendous handling and
wear problems at the same time. So, to avoid these problems, the
preload from ordinary spring packs must be reduced to a level
that renders them ineffective at preventing loss of drive. The
Wavetrac is the only differential that can automatically add
more load internally when it’s required.
In the case where
both wheels are on the ground during zero axle load, such as
during a transition to deceleration, the Wavetrac device is able
to prepare the drive train for when the zero torque condition
stops, eliminating the delay seen with ordinary gear diffs.
What this means
for you as a driver is that power is delivered to the gripping
wheels for more time and in a more constant manner – making you
faster and improving stability.
The Wavetrac truly is
different - and its innovative features can make a real difference
in your car’s performance.
Here’s something else you won’t find in any
The Wavetrac diff’s
behavior can be altered in the field to suit your needs. It comes
standard with carbon-fiber bias plates for the best all
around performance and lifetime durability. Changeable plates using
materials with different friction coefficients to fine-tune the bias
ratio are sold separately.
These bias plates
provide a mechanism to tune the response of the differential as a
function of applied torque load. The applied torque load manifests
itself as an axial load from the differential pinions into the
housing. This axial force is then considered a normal force into the
bias plate, and as a function of the effective coefficient of
friction, provide a resistive torque to the rotational motion of the
differential pinions. The resistive torque will add to the
resistance of relative rotation of all components within the
differential. The resistive force, however, is non-uniform since it
is a function of the axial load from the differential pinions. The
unbalance of the resistive torque will manifest as non-uniform
energy absorption within the differential causing a bias ratio.
Here are more features that make Wavetrac even
new Wavetrac Differential brings current gear technology to the
gear tooth forms are optimized for strength and improved oil
film retention over competitive designs.
Our gear package
is smaller, reducing overall mass, yet is more durable since
particular attention was paid to the tooth strength - optimized
for high torque conditions.
also paid to the side gear/axle interface, putting as much
material thickness as possible in this critical area - most
important when power levels get high.
Each Wavetrac Differential is crafted from the highest quality
gears are made from high strength 9310 alloy steel.
The diff bodies
are machined from case-hardened steel billet.
To complete the
package, every Wavetrac differential is built exclusively using
high quality, high strength fasteners from ARP®, the world
leader in fastener technology.
|Our new Install Kit allows fitment of a
Wavetrac differential in late-model rear axles of 135i and 335i models
where the ring gear is factory welded to the standard differential.
Since March, 2007 production, BMW has fitted
rear axles where the ring gear is welded to the differential carrier.
Until now, this process has hindered enthusiast owners’ ability to
upgrade, but no longer: Autotech Driveline now offers a precision
solution at a reasonable price.
receipt of a customer’s differential/ring gear assembly, the ring gear
is separated from the stock diff using CNC equipment. The ring gear is
then machined, drilled and threaded to allow bolt mounting to a new
We then return to the customer:
• Wavetrac Differential
• Customer’s machined ring gear
• Precision-ground spacer ring
• Set of 10 ARP ring gear bolts
For the best possible performance,
disassembly of the stock axle, and fitment of the Wavetrac and Install
Kit should be performed by one of our Specialist Dealers. This ensures
that the condition of the axle can be assessed before modifications are
performed, and that the re-assembly is done professionally - ensuring
correct gear backlash and bearing end play.