"Will It Go 'Round In Circles? You Bet!"

March - April 2001 Lane Racing And Rodding Article By Jim Kaekel, Jr.

The aluminum Powerglide automatic transmission debuted in 1962 and was produced until 1973. It was used at one time or another in just about all GM passenger cars, serving faithfully in everything from six-cylinder Novas to 427 Corvettes.

Though this transmission was very popular with the "grocery getter" crowd, performance enthusiasts largely neglected the 'Glide because of its two speed design and tall low gear ratios-1.76 or 1.82-which made it rather sluggish off the line.

It was not until the early seventies that innovators like Marv Ripes (A-1 Transmissions) took a serious look at the Powerglide's potential as a racing transmission. They were impressed by its low static and rotating weight, durability, and low cost.

The 'Glide was first applied to drag race applications, however it was not long before specially modified Powerglides found their way into the circle track arena, too.

One of the first circle track Powerglides was the "Circlematic", introduced by TCI Automotive. On the Circlematic, the converter was replaced by a direct pump drive which reduced rotating mass by as much as 20 pounds and eliminated slippage and lost horsepower.

Within a few years, JW Performance Transmissions, Coan Engineering, and many others began to offer their own units and Powerglides continued to grow in popularity.

During a recent conversation with Scott Miller of TCI, he emphasized that the Powerglide's low weight, durability and affordability continue to make it very attractive to the budget conscious racer. Complete units can be purchased for $600 to $800 less than four-speed manual set-ups; and once they're installed, Powerglides require less maintenance. Today they are common in Modified and Street Stock classes within sanctioning bodies like UMP, WISSOTA, and IMCA.

Because of the Powerglide's popularity, a tremendous number of aftermarket items have been developed over the years to make it an even better, more efficient transmission. It's a fact that a Powerglide may be almost completely assembled using only aftermarket components.

Recently, JW and Coan Engineering developed completely new, direct drive Powerglide transmissions for oval track racing.

According to company spokesperson, Tracy Winters, the JW unit uses an electric neutral valve body. It appears to be similar to a drag race unit-complete with trans-brake solenoid-but this solenoid, activated by a toggle switch, actually controls oil pressure for easy shifting between gears.

Coan Engineering's new Circle Track II transmission is completely "hands free" (no clutch pedal/master cylinder assembly is required). Jason Coan, of Coan Transmissions, tells us that the transmission uses a special valve body that provides a controlled pressure leak when it's placed in low or reverse to prevent harsh shifting. Full power may be applied once the transmission is shifted into high gear.

Unlike today's racing Powerglides, early circle track racing versions were "externally valved," that is, they used external pressure and return oil lines which were routed from the pump to a hydraulic valve mounted within easy reach of the driver. The driver could dump the oil pressure when changing from park or neutral to drive or reverse.

Most modern units employ internally valved systems, including special valve bodies that work in conjunction with hydraulic clutch and master cylinder assemblies. Since the converter is completely eliminated, the pump is connected directly to the crankshaft. The clutch pedal-actually more of an "engagement" pedal-is connected to a detent lever which, in turn, is connected to the valve body.

Driving a race car with one of these Powerglides is not unlike driving a car with a standard transmission. To take off, you depress the clutch pedal, feather the throttle slightly, and slowly release the pedal. Once the vehicle is underway, the transmission may be shifted into high gear at any time without using the pedal.

The Powerglide as a racing transmission is relatively trouble free, but the case and tailshaft are easily broken if a solid mount is used. OEM input shafts are susceptible to breakage on asphalt cars, especially if traction is exceptional, but this problem is easily solved by replacing the stock shaft with a heavy duty one available from TCI, Coan, or JW Performance.

It may be time for you-and your circle track racing customers-to reconsider this proven transmission. Give the 'Glide a chance!

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