Dale Amy
September 1, 2002

Horse Sense:
The terms "AODE" and "4R70W" refer to the same transmission family, differing only in gear ratios. The W in 4R70W refers to a wide-ratio gearset, most commonly found in light trucks, but also used in some car applications.

Good news. The self-shifting savants at Lentech Automatics have engineered a trans-brake valvebody for the electronically controlled AODE/4R70W transmission. One that actually works. We point out this latter fact because it's apparently not easy to adapt the AODE's electronically overseen valvebody for transbrake duty.

For those unaware, a transbrake allows revving the engine to launch rpm, in gear at the starting line, with-out having a foot on the brake pedal. It does this by actuating the automatic transmission's Reverse and Forward clutches simultaneously. A solenoid activated by a momentary-contact switch in the cockpit overrides the normal hydraulic circuitry of the valvebody to trick the clutch packs into this abnormal behavior. In other words, the transmission is actually in Forward and Reverse at the same time, so that, despite a madly spinning input shaft as you wait for the Tree, the output shaft temporarily does even less work than Editor Turner on a football Sunday.

The biggest challenge in designing a transbrake for the AODE is that its valvebody is missing many of the hydro-mechanical valves of a nonelectronic tranny's, such as the older AOD (the AODE uses electric solenoids under control of the EEC V in place of valves). Some of those missing mechanical components-for instance the Low servo modulator-were instrumental in how a traditional transbrake would function. In the absence of these various bits, an entirely new solution had to be sought.

Harnessing his unique genius for comprehending the seemingly incomprehensible maze of goings-on inside a valvebody, Lentech's Len Bertrand engineered not only a way to build an AODE transbrake valvebody, but also one that would function in either manual First gear or in Drive (transbrakes traditionally only work in First). And, as with Lentech's AOD transbrake, the AODE version permits normal Reverse operation without holding the transbrake button.

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In all, because of the AODE's unique electronic architecture, adding the transbrake required some fairly serious hydraulic replumbing and modification of valvebody function, including abandoning the factory pressure modulation system in favor of operation at a constant line pressure. A good transbrake must disengage the Reverse clutch virtually instantaneously as the button is released, something Len was careful to achieve with his hydraulic modifications. Using a fairly high, constant line pressure greatly adds to the transmission's ability to deal with increased horsepower, but it also provides this quick and consistent release of the 'brake.

But listen up. Though of no concern to racers-the people for whom the transbrake is intended-this unmodulated line pressure of Lentech's AODE Strip Terminator valvebody will provide shift characteristics aggressive enough under even light throttle to likely be bothersome on a daily commuter. Constant pressure can also be hard on seals over the long term. "It's not a valvebody that's meant for an everyday street car expected to go 200,000 miles," Len warns. "It's meant for racing, or for a limited-street-use car, as is any transbrake." For those who simply want improved shift quality and reliability in their AODE, Lentech offers a nontransbrake valvebody, called the Street Terminator, for $369.

You can order the AODE Strip Terminator transbrake valvebody, with or without provision for converter clutch operation, for $599. The choice is yours: Eliminating converter clutch operation (and thereby lockup) may actually slow e.t. and mph ever so slightly. On the other hand, if you don't have a converter with a well-made clutch assembly, "It's gonna be tough," Len says, "to keep that converter clutch together with anything over 400 or 500 hp." Either way, in addition to this valvebody's transbrake function, its characteristics should substantially raise the power-handling capability of an otherwise-healthy AODE while still offering full-if decidedly firm-automatic shift operation.

Among the first to order Lentech's AODE Strip Terminator transbrake valvebody was Paul Svinicki, for installation on the Paul's High Performance DragPak Stage II raced by Scott Baumgartner. Scott was thrilled to learn he wouldn't have to foot brake in 2002, knowing he'd be much more consistent.

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