The overdrive transmission was Detroit's secret weapon in battling fuel economy regulations in the '80s, but it soon became a means for hot rodders to have their cake and eat it too. Initially, Detroit merged the new overdrive transmissions with lock-up torque converters and 3.08:1 final-drive ratios for maximum thriftiness, but just a few years later, the overdrive automatic became an integral part of Detroit's musclecar renaissance, allowing the return of factory-issued 3.42 and 3.73 gears without upsetting CAFE standards. Car crafters were soon installing these same overdrives in their older street machines to permit leisurely cruising on the highway while still running deep gears.
The first overdrives were mechanically controlled, like the two- and three-speed automatics they replaced. But in the '90s, Detroit made the switch to computer-controlled transmissions that rely on electronics to determine shift timing and integrity. Of course, this requires an electronic processor, and most of the vehicles that were originally equipped with these transmissions contained the required electronics in the same computer that controlled the engine. In the case of General Motors, the popular TH700-R4 four-speed automatic evolved into the 4L60E. The change in the name is mostly due to a change in GM's transmission nomenclature, as a 4L60 is actually basically the same as a TH700-R4; it's the "E" part-denoting electronic controls-that makes all the difference. The TH200-4R didn't make the transition to the electronic age, but on the heavy-duty side, GM introduced the 4L80E, an overdrive version of the tough TH400.
From the factory, the 4L60E saw use in the Camaro/Firebird twins, the Caprice/Impala line, and the Corvette, as well as in light-duty pick-ups and SUVs. The 4L80E has been limited to heavier truck applications, like 31/44-ton pickups, Suburbans, and the like. The good news for owners of these vehicles is that now, instead of having to delve into the transmission itself in order to alter the timing of the shifts and increase their authority, the transmission can be reprogrammed to achieve the same results. However, the bad news was the average Joe had no way of doing this on his own, at least initially. Fortunately, the aftermarket came to the rescue, offering several means of plugging into an electronically controlled vehicle to achieve more performance-oriented shifting. Most of these are more involved than the old chip swap methods of reprogramming, since factory electronics are significantly more sophisticated. We've rounded up the current crop of transmission tuners for the GM electronic automatics and listed the features of each for your perusal. Now, there are no more excuses for mushy, premature shifts.
Jet PerformanceAlthough known for late-model performance enhancements, Jet offers a wide variety of hardware upgrades for a broad spectrum of vehicles. Included in its palate of services are complete automatic transmission packages (overdrive and non-OD), overdrive transmission swap kits (for non-OD vehicles), carburetor refurbishment and power tuning, ignition enhancements, and fuel-injection upgrades. There are actually several items listed in Jet's catalog to improve the performance of GM's electronic overdrives, but we'll focus on the Power Shift module.
What it is: Jet Performance Power ShiftWhat it does: Provides the ability to select between four different settings for progressively increased shift firmness. The first setting is stock, which is followed by Stage I, II, and III, with the third stage providing the hardest shifts.How to install/use it: The Power Shift unit simply connects inline with the transmission's original wiring harness. It's a plug-in deal, so no splicing is required, and it can be removed at any time to return the vehicle to stock. The unit is controlled via a dash-mounted panel, with indicators to show which stage is engaged. Changing modes is simply a matter of touching a button.
Additional features: Also available is the Power Shift Plus, which includes actual hard parts to be installed in the transmission to further improve shift quality. This is similar to shift-improvement kits used with conventional transmissions, requiring minor modifications to the valvebody. The Power Shift Plus also includes a fresh trans filter and pan gasket.
HypertechOne of the original tuners of electronically controlled vehicles, Hypertech has continued to crack the secrets of Detroit's mysterious black boxes in the name of improved performance. These days, instead of offering only preprogrammed performance chips, Hypertech now manufactures a line of hand-held programming devices that allow even the most technically challenged car crafters to alter the inner workings of their vehicle's PCM for enhanced performance. The Power Programmer can change the parameters of numerous functions in late-model GM PCMs, including transmission shift points and firmness.
What it is: Hypertech Power ProgrammerWhat it does: Provides the option of altering the parameters of multiple PCM functionsHow to install/use it: The Power Programmer is a hand-held unit, about the size of a typical electronic multi-tester, and includes a patch cord that plugs into the vehicle's diagnostic port, usually located inside the vehicle, under the dash. Once connected, the user simply pages through the various functions, choosing whether to leave them stock or select from one of the optional alterations. For the transmission, the Power Programmer can provide several levels of increased firmness, plus adjustment of the shift points.
Additional features: The Programmer can also make adjustments in calibration to accommodate changes in rearend gear ratio and tire height, both of which will negatively affect transmission performance if not compensated for electronically. The Power Programmer also provides adjustments for spark timing, rpm limiter, top-speed limiter, and cooling-fan activation.
Applications: (Check the Hypertech Web site for specific part numbers.)'94-'97 LT1 Camaro/Firebird'98-'02 LS1 Camaro/Firebird'01-'02 3.8L V-6 Camaro/Firebird'96 LT1 Corvette'96 LT4 Corvette'97-'03 LS1 Corvette'94-'96 LT1 Impala SS/Caprice '96-'03 V-6 and V-8 truck
SuperchipsAnother long-time computer tuner is Superchips, which began by tweaking the electronic controls of European performance machines for both the street and the track back in 1983. The company began U.S. operations in 1992 in Florida. Like many of the original electronic enablers, Superchips started by producing aftermarket PROM chips for '80s-era performance iron and has continued to evolve right along with the auto industry's technology. Today it offers tuning enhancements for the current crop of performance cars from Detroit, along with truck and SUV applications, and some of the hottest stuff from overseas.
What it is: Superchips MicrotunerWhat it does: The handheld device provides a performance-enhancing base program, which can then be switched for more aggressive programs. It also allows for adjusting certain parameters individually, including transmission shift points and firmness.
How to install/use it: The device plugs into the vehicle diagnostic link and begins with a base program, which is a mild enhancement on stock programming. This slightly raises the shift points and increases shift pressures, as well as limits the amount of timing retard imposed during shifts. The user then has the option of raising or lowering the shift points from the base program; shift points can usually be lowered back to stock, but not below. Shift firmness can also be further adjusted.
Additional features: In addition to the base program installed by the Microtuner, there are other complete programs to select from that have been mapped out by the Superchips engineers based on dyno and road test research. For trucks, there are usually several to choose from, including a low-octane performance mode, high-octane towing mode, and high-octane performance mode. Corvettes and F-cars typically have only one additional program, as these cars are intended for premium fuel by the manufacturer and are programmed fairly aggressively from the factory. There are different menus for different functions with individual features, including the ability to raise the vehicle speed limiter and engine rev limiter and the option to change the cooling fan activation temperature.
Applications: 2725: '99-'03 V-8 Camaro, Firebird, and Corvette; 2715: All GM V-8 trucks from '96-'03
DiablosportTo the average enthusiast of late-model performance, Diablosport probably seems like the Johnny-come-lately of the electronic tuning arena, but its roots run much deeper. Though the Diablosport line has only been available for the past three years, the parent company-ProgRama Tools-has been in the business of designing and manufacturing automotive electronic diagnostic equipment for decades. Other divisions of the Rama Group are dedicated to remanufacturing OE automotive electronics, including engine- and drivetrain-management control units. This background enabled Diablosport to move rapidly from its launch to its current position as a noted source of performance tuning equipment in a relatively short time.
What it is: Diablosport PredatorWhat it does: Provides a more aggressive basic program to the vehicle's PCM, which can then be adjusted on multiple parameters
How to install/use it: The Predator is also of the handheld variety, plugging into the vehicle's diagnostic port using the supplied patch cord. Once the basic Predator program has been installed, the user has the option of selecting from other, more aggressive programs. In addition, the user can also adjust certain parameters individually. The automatic transmission shift points and firmness are among the parameters that can be altered independently.
Additional features: The Predator also allows the user to fine-tune the fuel and ignition curves of the Diablosport base program, as well as provide the ability to raise the engine rpm limit, the vehicle top speed limit, and allowing for changes in rearend gear ratio and overall tire height. The Predator can also function as a diagnostic tool, reading trouble codes and monitoring engine functions in real time.
Applications:'99-'02 LS1 Camaro/Firebird'99-'03 LS1 Corvette'99-'03 GM light truck and SUV
Motorsports Technologies Inc.Perhaps better known by its MTI abbreviation, Motorsport Technologies is currently celebrating its tenth year of operation, offering a broad spectrum of performance parts and services for late-model GM high-performance vehicles. In addition to serving as a distributor for various manufacturer's wares, MTI also produces some of its own performance parts, as well as offering a complete engine-building service. Cylinder-head and camshaft packages for GM's Gen III small-block are a specialty, with dyno-tuned programming available to make it all function properly. In fact, an MTI-prepped Corvette Z06 recently took top honors at the 2003 Car & Driver One Lap of America event.
What it is: MTI custom-programmed late-model GM PCM drivetrain management unit
What it does: Resets the calibration for whatever parameters are specified by the customer, including automatic transmission shift points and firmness.
How to install/use it: This is more of a service than an actual hard part, since in most cases, MTI is taking in an original PCM, reprogramming it (termed "reflash" in the industry), and then returning it to the customer. The customer removes the PCM, ships it to MTI in Houston, Texas, and then receives it back in several business days (overnight service is available for an extra cost). The unit is reinstalled and the new programming immediately takes effect. If for any reason the customer is dissatisfied with any of the changes, the unit can be returned and re-tuned to remedy the situation at no extra cost during the first 15 days.
Additional features: Since the PCM is being reflashed, any of the typical performance parameters can be altered during the process, including rpm limits, top speed limits, fuel and spark curves, calibrations to accommodate aftermarket airflow meters, larger injectors, aggressive camshafts, and so on. Entire performance programs are also available for particular combinations.Applications: Any vehicle with a PCM
B&M Racing What it is: B&M ShiftPlus What it does: Recalibrates transmission programming to increase performance, offering two performance modes in addition to stockHow to use/install it: The ShiftPlus is a simple module with a hard-wired control panel. It connects to the factory PCM harness, and then the control panel is mounted in the cabin. The user has the option of selecting from two performance modes, one with more positive shifts for heavy-duty use, like towing, and another for street/strip performance, with much firmer shifts and higher shift points. The user can also elect to turn the unit off, which allows the PCM to run stock programming. B&M claims the unit can be installed in minutes and that it will reduce heat and slippage during extreme use.Applications: PN 70380: '94-'96 Caprice/Impala; '93-'98 Camaro/Firebird; '94-'98 Corvette, '93-'98 Suburban, Tahoe, Blazer, and 1500/2500/3500-series pickups with MT1 or M30 transmission code
FastchipVeteran racer and tuner Ed Wright offers his 30-plus years of performance experience to late-model GM vehicle owners looking to improve the performance of their cars through enhanced calibration. Fastchip doesn't delve into hard parts, limiting its work to altering the electronic tuning of the vehicle's engine management unit to accomplish the desired goals. Of course, there's only so much that can be done with stock hardware, but once you've maximized the potential of the factory equipment, Wright can continue to tweak your computer to take full advantage of any other modifications made. As with most of the other tuning methods, transmission shifting and firmness can also be altered by Fastchip.
What it is: Fastchip PCM reflash program What it does: Alters the factory drivetrain management calibrations to increase performance
How to use/install it: In most cases the original PCM must be removed, sent to Fastchip to be reprogrammed, and then returned to the customer, who reinstalls the unit. Fastchip also offers an exchange program for those who can't afford downtime. As is the case with most of the tuning methods we've covered, Fastchip can alter shift timing and firmness, as well as the "torque management" of each shift-a term that refers to the amount of ignition-timing retard during shifts and the time it takes for the shift to be executed. Wright points out that the characteristics of each shift can be programmed individually, and if desired, the really firm shifts can be limited to wide-open-throttle operation only. As an aside, Wright points out that there were a few models produced by GM that used the 4L60E and 4L80E with E-PROM type computers, though all were trucks. For the 4L60E, these included '93-'95 11/42-ton pickups and vans, and for the 4L80E, the '91-'95 31/44- and 1-ton trucks. Fastchip can also recalibrate these vehicles using a new chip.
Additional features: Since the PCM is being reflashed, there are many parameters that can be adjusted at the same time. Customers can request specific changes, though Wright can also make recommendations for tuning changes based on the combination of parts and intended use. Typically, the biggest performance gains are seen on trucks, with 454-equipped models seeing as much as 35hp increases in some instances. Fourth-gen Camaros and Firebirds will see about 10-12 hp with stock hardware, while Impalas and Caprices can pick up as much as 12-14 hp. Wright can also reprogram PCMs to accept other changes, like larger airflow meters or throttle bodies, larger injectors, and so on.
Applications: Fastchip can reprogram V-8-equipped Camaros and Firebirds all the way back to the '85 model year; the same goes for Corvettes. Truck applications include most throttle-body-equipped V-8 engines as well as Vortec V-8 engines.
