To tune the SuperMatic to your Pontiac, put away the wrenches and take out the laptop.
When HPP teamed with GM Performance Parts (GMPP) and Classic Restorations to mate the new THM 4L85-E SuperMatic transmission to a built-to-the-hilt SD-455, we wanted to fully document the process. Thus previous issues covered in great depth the internal workings of the SuperMatic, along with the physical installation into a '74 Trans Am (Feb., Mar., and Apr. '10, or check online at highperformancepontiac.com).
The last installment was dedicated to the cooling and electronic controls that are required to integrate the SuperMatic with the traditional-but-modified Pontiac engine. The 455 in this T/A was also the subject of an in-depth engine build and dyno sessions (both engine and chassis) a few years ago, which included the testing of a new EFI system. The result is an electronic-fuel-injected SD T/A with a state-of-the-art microprocessor-controlled transmission-a vintage Pontiac with almost as many computer chips under the hood as an '09 model.
The SuperMatic possesses many virtues, such as the ability to withstand a huge amount of torque (685 lb-ft), along with an overdrive gear ratio (0.75:1). During our work with the SuperMatic, HPP had the opportunity to talk with Jayson Schwalm and John Boughner. Jayson was the lead calibration engineer on the OE installation of the 4L85-E; John was the calibration manager. They told us it was designed to pass the rigorous GM test of lasting 200,000 miles under a full torque load when connected to a Duramax Diesel in a GM van (a factory application for this transmission). They both said simultaneously that the 4L85-E passed with flying colors.
We securely mounted the TCU under the hood of the Firebird.
Jayson continued: "The lessons learned when designing, manufacturing, and calibrating the 4L85-E are responsible for GM's ability to offer a 100,000-mile powertrain warranty on all of its 2010 model cars and light-duty trucks. That warranty proves GM quality to the consumer and is not matched by any competitor in the marketplace right now." And the 4L85-E SuperMatic is even stronger.
It's now time to explore the transmission's ability for end-user programming of almost every operating function, which is accomplished though the use of a laptop, dedicated software, and an interface cable that talks to the microprocessor in the TCU (transmission control unit). This transmission allows the shift strategy to be altered in the way a valvebody shift kit would, but with one big difference-it's done by the stroke of a keyboard with no wrenches required.
This exciting capability will allow you to completely tune the SuperMatic to your driving style, requirements, and the torque and horsepower of the engine in your Pontiac. No longer will you be forced to make compromises in shift quality and rpm point or feel, or be tethered to a transmission shop to try and get it the way you want it.
The calibration process begins by telling the TCU how you want it to communicate with the
Thinking Like A Calibrator
Before we delve into the tuning points of the SuperMatic, a few things need to be established. The 4L85-E is still an automatic transmission. It does not operate through electronics. The dynamics of hydraulic fluid flow are still as relevant as in any self-shifter. Its valvebody with all of its pistons, springs, check balls, and calibrated orifices has been replaced by electronic solenoids. The transmission fluid still does the work, but instead of a traditional mechanical/hydraulic design, the SuperMatic is a hydraulic/mechanical/electronic system. Thus the torque converter, planetary gear set, and the like still operate in a similar fashion to a THM 350 or 400.
The benefit of the electronic controls is a finite and wider range of tuning than would be allowed with springs and check balls. When dealing with a strictly mechanical valvebody, whatever compromises necessary are often accepted. For example, the shift quality at light load may end up being too hard for your liking, but it's required for the proper amount of clutch pressure under full power.
Even the best transmission guru would often have to accept a comprimise in one operating range for the proper performance at the track. Though neck-snapping part-throttle shifts may seem cool at first, they are not desirable over the long haul. With the SuperMatic, that will no longer be the case, as you can have your cake and eat it too.
The dashboard function can be programmed to show a variety of data from the TCU.
A dashboard screen works like a scan tool. It provides a quick view of the inputs into the
The Global Setup Parameters are where information specific to your Pontiac is entered. Not