When it comes to applying the latest technology to street rods some of us are more enthusiastic than others. If nuclear powerplants suddenly became available you can be sure Brennan would shoehorn a reactor under the hood of his highboy. Then there are those of us who are skeptics. Not to name names (editor’s note: this from a man whose calendar ended in 1967!), we all know guys who held back on the newest whatchamacallit until it was proven, who chose to stick with eight-tracks because cassettes would never catch on, and who believed points were superior to electronic ignition because you could always adjust those simple breakers out in the middle of nowhere, but if a module died you’d be stuck (editor’s note: Ron is unaware that you can purchase extra modules to place under the seat—where he keeps his Cheetos!).

The truth is today most of us have been listening to CDs for some time, haven’t changed a set of points in years, and have come to believe computers and hot rods are no longer mutually exclusive. Little black boxes of some sort are in and run almost everything in a contemporary automobile and there’s no arguing that performance and longevity have improved as a result and more of that technology is finding its way into our hobby on a daily basis. One of the most recent advancements to impact our world are the variety of computer-controlled automatic transmissions that are now available.

With the introduction of automatic overdrive transmissions, rodders found they could have the best of both worlds: a transmission with a low First gear for off-the-line acceleration, and an overdrive gear of more economical highway cruising. When first introduced, these overdrive transmissions used controls that were similar to their three-speed predecessors, mechanical throttle valve linkages, vacuum switches, internal governors, and so on. But it didn’t take long for the OEMs to figure out a better way was to use a computer that allowed the engine and transmission management systems to communicate with each other. Unfortunately, for our purposes that meant that installing computer-controlled transmissions in street rods was going to require stand-alone electronics.

Much like the early retrofit fuel injection systems, most of the first aftermarket transmission controllers had to be programmed with a laptop and for many rodders that was enough to make stay away; after all we’re talking about some guys who still have clocks blinking on their VCRs. Fortunately there are now controllers that are plug-and-play, like the Compushift II from HGM Automotive Electronics. The guys behind HGM today are Mike Hoy, who has been in the transmission business since the ’60s and Guy Cardwell, an electrical engineer, who Hoy describes as the sharpest guy he knows in electronics.

As Hoy explains it, without a controller these modern transmissions are literally “brain dead.” However, with a properly designed management system they are tunable to provide high performance for a variety of applications. Computers offer total control of shift points, shift quality, and converter lockup. And from our standpoint the best thing about them is they totally eliminate finicky and problematic throttle cable adjustments. In simple terms, these computers control the transmission based on the input they’re provided from a variety of sensors, such as:

Transmission Output Shaft Speed (TOSS) Sensor: As the name implies, it measures the speed of the driveshaft. This sensor can also supply a signal for an electronic speedometer. However the TOSS signal for the computer should never be connected to the speedometer; there is a wire called “reproduced TOSS” for that purpose.

Throttle Position Sensor (TPS): Again, as the name implies, this sensor detects the position or opening of the throttle. In the case of engines with electronic fuel injection the existing TPS can be used. For carbureted applications HGM offers an add-on TPS with a bracket to mount it and a link to connect it.