Reprogramming Your Chevrolet Corvette's Automatic Transmission - Shifty Business

Changing a 700-R4's Character With a TransGo Performance Shift Kit

John Nelson Nov 1, 2002 0 Comment(s)
Vemp_0211_01_z Reprogramming_chevrolet_corvettes_automatic_transmission Shift_kit 1/21

Automatic transmission technology has advanced by leaps and bounds since the early days of Fluid Drives, Dynaflows, and Powerglides. The General took giant steps when it replaced the Turbo 350 with the TH 700-R4 four-speed automatic transmission in 1982; this same basic unit (now electronically controlled and called a 4L60E) handles gearbox duties in Corvette (albeit in a highly modified form for the C5) and other brands to this day. In fact, automatics handle these duties in most Corvettes. Starting with the '72 model year, sales of shift-it-yourself Vettes dropped below those of automatic-equipped cars, and that's the way it's been ever since.

This certainly makes sense for the OEMs. Automatic transmissions allow the factory to control factors such as fuel economy and emissions by controlling when the transmission shifts gears. This gear selection, in turn, is second only to the accelerator in determining what speed an engine runs at. This arrangement is also satisfactory for the vast majority of motorists. I don't know that I'm old enough to be a diehard, but it's always seemed to me that sports cars 'oughta have a manual gearbox. Computer controls notwithstanding, it takes driver input via gearbox and clutch to pick the perfect engine speed for a given driving situation-which is why us "diehards" spend so much time contorting our ankles into position for heel-toe maneuvers.

That being said, I now must admit that my own Corvette, an '84 I've labeled "The Bronze Bomber," has an automatic transmission. Despite the desire to row my own, transmission preference took second place to getting the best Corvette for the money I had. My first thought, transmission wise, was "So this is why they call them slushboxes." The shifts themselves were slow, and always happening too soon, leaving me in a higher gear than I would've liked. This was especially true when driving in the "OD" position; even a Corvette doesn't feel very performance oriented at 25 mph in Fourth gear.

Vemp_0211_06_z Reprogramming_chevrolet_corvettes_automatic_transmission Electrical_connector 2/21

With the console door opened, use a small, flat-blade screwdriver to pry the traction control up and out to access several of the console retaining nuts. Unplug the switch from its harness and the electrical connector from the accessory power outlet.

The scary thing is, my '84s 700-R4 was in perfect working order. By their very nature, from-the-OEM automatic transmissions are imprecise creatures- especially when the slushbox in question is a first-generation 700-R4. And in performance applications-like autocrossing-durability questions arise as well. One solution is to remove the transmission and have it re-built to hi-po specs. Another-the route I took-is to re-program the stock unit. Of course, I wanted civilized street behavior along with increased performance when it comes time to do a little racing.

Here's a grossly oversimplified version of how an automatic transmission works: the gears within are engaged in various combinations to create a given gear ratio. Which gears are engaged, how they're engaged, and when they're engaged, is controlled by "bands," which either hold a given gear in place or allow it to turn. The servos that activate these bands are in-turn controlled by hydraulic pressure-that's transmission fluid to you and me-which is controlled by a number of valves that reside in the transmission's valvebody.

That being said, here's the deal: We can't change the gears in a transmission, but we can alter how and when it shifts by altering the valvebody-and that's exactly what TransGo does with its Performance Shift Kits. The PSK is a do-it-yourself kit, and to put it briefly, it changed the character of my 700-R4.

"The original system is always designed so that when mamma drives the car, there won't be any complaints," according to TransGo founder Gil Younger. "With our design, we do everything that we can to add performance and durability without getting a 'rough complaint' at light throttle."

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