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John Kilgore Proudly uses Alto Red Eagle Clutches

Super Chevy Magazine explains how the Superlite works:

A Strong Turbo 400 Doesn't Have To Weigh A Ton

By Jason Walkner, August 2001 issue

Super Chevy Magazine

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.

For 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 i
nternals 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.

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.

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.

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.

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).

Thinner 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


Kilgore Transmissions &
Weld-Done Services
727 Ruberta Ave., Dept. SC
Glendale, CA 91201

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Contact John Kilgore at 818-767-4480, or at
11132 Fleetwood St., Unit C
Sun Valley, CA 91352

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