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Super Chevy Magazine explains how the Superlite works:
POWER TO WEIGHT A Strong Turbo 400 Doesn't Have To Weigh A Ton
By Jason Walkner, August 2001 issue
One of the most tried and true methods for building a faster
race car is making an effort to eliminate excess weight from
the body, chassis, and any other significant parts that are
sure to cause slower track times as well as added strain on
the engine. As the old saying goes, there's no better way to
improve performance than by improving the power-to-weight ratio.
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this story, we want to address the problem of heavy internal transmission
parts and how they slow the power distribution, which causes a
notable loss in horsepower from the engine to the drive shaft.
To explore this problem further, we contacted John Kilgore, who
has been building race-proven transmissions for longer fro more
than 30 years. Kilgore's philosophy on building a better TH400
- the tried and true workhorse of racing automatic gearboxes -
starts out with simple laws of physics: the heavier an object
is the more power it will take to move. The answer then seems
pretty simple; why not lighten it up?
To begin with, there is an incredible amount
of inertia produced inside an automatic transmission. For example,
shifting from First gear to Second gear, will mean instantly stopping
the 14-pound direct drum, which is turning at 84 percent engine
speed, while the 8-pound front reaction carrier starts turning
at 50 percent engine speed. All of this happens in the short time
it takes to shift gears. Additionally, there is an equal amount
of force generated when shifting in and out of all three gears.
Keep in mind, when General Motors designed the TH400, it was for
an entirely different purpose than racing. The Turbo 400 had to
handle the torque of a big-block powerhouse as well as deliver
a comfortable and reliable drive. This is the reasoning behind
having heavy internal parts. |
On the left is the lightweight Kilgore TH400 internals
compared with those from a factory unit. What you can't see is
the 30-plus pounds removed from the OEM TH400 parts. |
What Kilgore has done to whittle away at this
problem is use lighter parts to make a better transfer of power.
The components used inside one of Kilgore's TH400s, adds up
to losing an amazing 30 pounds of reciprocating mass! This may
not seem overly significant, until we consider most of that
30 pounds is stopping and starting instantly at a very high
rpm, under extreme stress, no less.
In addition to the weight savings, the use of smaller hollow
hubs, in lieu of the oversize and "weighty" factory
TH400 drums, allows more space so that twice as many friction
disks (or clutch disks) can be employed. Since friction disks
are what stop the drums, it goes without saying that more is
better. The added space also leaves room for thicker steel friction
disks, which get sandwiched between the clutch disks and add
much more cooling surface than their thinner counterparts.
Not only is Kilgore's TH400 lighter, but when used with the
correct gear rations, it becomes a bullet-proof automatic to
launch any high-torque, big- or small-block racer down the quarter
mile easily an reliably. So follow along as we go about putting
a basic TH400 on a weight-reducing diet. We think you'll agree
that the finished product will make a difference in your massive
weekend warrior or obese boulevard bruiser.
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These two photos represent
what is happening when the transmission is in First gear.
The forward drum (or the
top drum) is turning with the same rpm in the engine, while the
direct drum (the lower drum) is turning 84 percent engine rpm
in the opposite direction. This gives us an idea of how much easier
it is for the transmission to spin and stop with the hubs in Kilgore's
tranny, compared to the heavy drums in the factory transmission.
Remember the factory drums are 14 pounds each, while the hubs
used in Kilgore's weigh about 4 pounds each.
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To shift from First gear
to Second gear, the tranny will need to sp the direct drum instantly
and start spinning the reaction carrier at 50% engine rpm. The
reaction carrier pictured on the near left is an 8-pound factory
piece, while the one shown on the far left is made of aluminum
weighing in a 4 pounds.
This means, the transmission
is working half as hard when shifting. Kilgore offers a reaction
carrier in sheet metal as well, which he designed to weigh less
than 3 pounds. All of these changes are done to relieve stress
on the rotating parts inside the trans, not just to make the transmission
lighter. |
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When the transmission
shifts into high gear, everything must now instantly turn at engine
speed. This means the direct drum is going from zero rpm to full
engine rpm immediately, while the reaction carrier jumps from
50 percent engine speed to full engine speed. This is a whole
lot of pressure on the rotating internal parts. Imagine stopping
or starting a 14-pound drum at 5,600 rpm instant. It makes good
sense to free the internal transmission parts from heavy rotation
when it is simply robbing horsepower from the engine.
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The top two pieces are
the factory reaction carrier assembly, while the lower two are
Kilgore's designed carrier assembly. The differences here are
not just weight, but also a change in rotating parts. Kilgore's
carrier changes rotation from the drum (lower left) to the hub
(lower right).
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frictions allow more plates to be added to the clutch pack, up
to ten in the direct clutch.
Kilgore uses high performance
Alto Red Eagle clutches |
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Sources: |
Kilgore
Transmissions &
Weld-Done Services
727 Ruberta Ave., Dept. SC
Glendale, CA 91201
818-246-9471 |
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