If it's mechanical, you can bet the OEs have it digitally controlled. This obsession with control started with electronic fuel injection in the late 1980s and eventually expanded into suspension and transmission control. All late-model overdrive automatics are now microprocessor managed, which makes converting one of these transmissions more expensive, since it requires a separate, stand-alone electronic controller. Car Craft did a complete comparison of six different transmission controllers for the 4L80E four-speed automatic overdrive transmission in the Mar. 2012 issue ("In Control"). These controllers all did a great job, yet the least expensive Powertrain Control Systems unit was still priced right around $600. This pushed us to look for a less expensive alternative. The first idea we ran across was a full-manual conversion kit from Trans-Go (PN 4L80E-3, $232.95 Summit Racing), which converts the 4L80E to full manual use. This conversion requires permanent modifications to mount a vacuum modulator valve to the valvebody. The old-school vacuum modulator is connected to engine manifold vacuum and adjusts trans line pressure based on throttle opening (load). As the throttle is opened to wide-open throttle (WOT), manifold vacuum approaches zero, which increases trans line pressure to ensure that the clutches see maximum hydraulic application pressure. The kit is not that expensive, but it does require removing the valvebody and a permanent change. To update the trans back to electronic control at a later date would require a new valvebody.
A little more digging revealed a product from Rossler Transmissions that owner Carl Rossler calls the Ross-Lock hybrid manual valvebody, or the "Little Black Box." It really is a small, black, plastic box that plugs into the 18-pin main 4L80E connector and is powered by switched 12 volts. When 12 volts is applied to the box, the transmission operates under full manual control. This means that whatever gear the shifter has selected—that's the gear the trans is in. What intrigued us was the simplicity of the installation. Mount the box on the trans, hook up switched 12 volts and switched ground to activate the torque converter clutch (if so equipped), and you are ready to rumble. It seemed too good to be true, so we bolted one in place to test.
We mounted the Little Black Box to the side of our 4L80E and plugged in the 18-pin connector, and we were more than halfway installed. It’s that simple. If you can fog a mirror, you can make the Ross-Lock box work.
We decided to try the Little Black Box on the same big-block 1970 Nova that had hosted our trans controller tests. It is still fitted with our torquey 590hp, 496ci Rat ("Big-Block Cylinder Head Test," Mar. 2008) and a boneyard refugee 4L80E trans. We disconnected the electronic controller, and in a matter of minutes we were back on the road. This conversion box effectively maxes out the transmission line pressure so that each gear change applies full hydraulic pressure regardless of load on the engine. If you've ever driven an older automatic transmission with a failed vacuum modulator, then you know what this can feel like. This makes any light-throttle shift just as harsh as at WOT.
Our 4L80E was a junkyard refugee, so it doesn't quite have the ultimate shift firmness that a new trans would offer, so the part-throttle shifts are most definitely firm but not neck-snapping. If the trans was new and modified for slightly higher line pressure, it could be really harsh. For a Pro Street–style car that does not see thousands of street miles, this could be acceptable. After driving our Nova for about 20 minutes in town at part throttle, the part-throttle shifts weren't annoying, and manually shifting the trans was no worse than driving a manual-trans car without the clutch. Another important point that should be mentioned is that the transmission pump must supply constant maximum line pressure, which means this places additional load on the pump gears and no doubt will contribute to shortening its lifespan. But other than the full manual control and harsh part-throttle upshifts, the advantage is that you've only spent $295.95, and it required perhaps 15 minutes to install. Rossler also makes a similar controller for the GM 4L60E transmission, too.
We are certainly taxing our 4L80E trans and controller with our 496ci Rat motor that made 626 lb-ft of torque at 4,000 rpm and 597 hp at 5,600. Even in this somewhat heavy Nova, this is a tire roaster on the street!
Based on our experience, as long as you're aware of the potential for harsh part-throttle shifts, we can say the Little Black Box makes for a simple, quick way to get an electronic GM trans on the road. Then, at some point, if you're looking for more sophisticated control, you could step up to one of the full-fledged controllers when your budget allows. For us, Rossler's Little Black Box delivers.
PARTS LIST Description PN Source Price 4L80E Ross-Lock Call Rossler Transmissions $295 4L60E Ross-Lock Call Rossler Transmissions $295
Once we wired the Little Black Box into the 4L80E in our ’70 Nova test car, we had instant manual trans control. We got lazy after a couple of jaunts, and our loose TCI converter allowed us to easily accelerate from a dead stop in Second gear.
