Manual Lever Position Sensor (MLPS): Ford uses this sensor, or a variation of it, to tell the computer what gear the transmission is in. On GM transmissions this function is done internally. While on the subject of Ford overdrives, they do have some unique features that we should point out. Like most transmissions Park, Reverse, and Neutral are standard shifter positions, but unlike many other four-speed overdrive automatics there are only three other shifter positions—D, which allows the transmission to shift through all four gears; 2, which locks the transmission in Second gear only (the vehicle starts in Second and stays there); and 1, which locks the transmission in First and keeps it there. What’s missing is a Third gear position, but while it may not be on the gearshift indicator it is available with the push of a button. The Compushift II comes with what is called a “cancel switch,” which prevents the transmission from shifting into Fourth (however the converter will still lock).

Installing the Compushift II controller is simple enough. It should be mounted away from any sources of extreme heat, and that includes the heater outlet. All the wires are clearly labeled; all the plugs are dedicated and will only fit in the proper place, but do yourself a favor and read the instruction before you begin installation. But if you have any questions the helpful tech guys are just a phone call away.

While the HGM Compushift II computer is an extremely smart device, it’s something simple that will dumb it down—a bad ground. After everything in your street rod is painted, plated, and powdercoated, it can be tough to find a good spot to ground electrical components, but a good ground is absolutely essential to the proper operation of the HGM system (as well as every other electrical device). That’s why HGM recommends grounding their system directly to the block (but the connection point still needs to be clean, bare metal).

Once installed no laptop is needed to program the Compushift II. The system is delivered with factory-set programming for a wide variety of transmission and engine combination, however a setup screen can be used to input information, such as number of engine cylinders, gear ratio, tire diameter, and more, if necessary. In addition a PC can be connected via the USB port for system software updates and advanced tuning if desired.

There’s no question that a computer offers the most precise control of today’s incredible overdrive automatics while allowing alterations for special circumstances. The Compushift II can be programmed to deliver neck-jerking shifts under full throttle, yet provide smooth driveability during light throttle and cruising—that’s real automagic.

Oh, by the way, anyone want to buy a box of eight-track tapes?

Basic Transmission Operation

To appreciate all the Compushift II can do, HGM believes it’s helpful to understand how an automatic transmission works.

The major components in your transmission include:
Torque Converter: A special fluid coupling that makes the connection between your transmission and engine. It drives the gears in the transmission, which in turn, moves the vehicle. This device has a special clutch called the “torque converter clutch” that directly connects the engine to the transmission in the same way a manual transmission clutch operates. This is usually done to improve fuel economy.

Hydraulic Pump: Pumps oil in the transmission to provide lubrication and pressure to actuate clutches, bands, and other components.

Control Solenoids: These electrically controlled valves turn oil pressure on and off in the valve body and adjust hydraulic pressure.

Valve Body: The valve body, in turn, routes oil pressure to the clutches and bands.

Gear sets: These are a combination of gears that mesh to provide a specific gear ratio. Any planetary gear set has three main components: sun gear, planet gears and the planet gears’ carrier, and ring gear.

Clutches and Bands: Clutches and bands alternatively connect and disconnect different gears in the transmission. The correct sequencing of band and clutch activation is what shifts the transmission.