Product Line
"Gearstar's lineup of performance GM transmissions includes the TH350, TH400, 700-R4, 200-4R, 4L60, 4L65, 4L70, 4L80, and 4L85. Although each is custom-built to a customer's specific needs, we offer several stages of strength to simplify selection. Our Level 1 units are completely remanufactured using improved Alto friction materials and a mild shift kit. They are capable of reliably handling up to 300 hp and are perfect for daily drivers. Our Level 2 transmissions are also remanufactured with all-new internal parts. In addition, the torque capacity of the clutch packs is increased by more than 70 percent, and a more sophisticated shift kit is used. They're rated at about 400 hp in a street-driven car. Gearstar's Level 3 transmissions are equipped with all hardened and stress-relieved hard parts, including shafts, drums, and planetaries. Additional modifications include three different shift kits, expanded-capacity clutch drums with racing friction materials, and hardened Kolene steels. They're rated at 500 hp in street/strip applications. Our Level 4 and 5 units are built to withstand the horsepower and torque of blower motors and high-horsepower stroker small-blocks. These transmissions have all of the Level 3 modifications, and all hard parts are made from 300M billet steel or billet aluminum. They come blueprinted, and Level 5 units include a lifetime warranty.

Complete Trans System
"When you call Gearstar for a new transmission, you are not getting an off-the-shelf unit. We custom-manufacture your automatic transmission and converter to your exact requirements and engine specifications. Every Gearstar transmission and converter package is handled as a project. It is assigned to a specific builder who will coordinate with the technician manufacturing your converter to produce the perfect transmission and converter package. Gearstar will not sell a transmission without a converter. The reason for this is that the converter is an integral part of the transmission. They share the fluid and work in tandem as a torque-transferring system. How can anyone warranty a transmission without manufacturing the converter? Additionally, Gearstar has a standard 24-month warranty, which is one of the best in the industry."

Shift Firmness
Firming up shifts can improve performance and sometimes trans life, but there is definitely a point of diminishing returns. In addition to lowering the comfort level for daily driving, too much shift firmness can result in excessive driveline shock and wear-and-tear. "Line pressure settings are basically a modified level of factory pressure rise," explains Farah. "Gearstar transmissions are internally modified to maximize line pressure through modifications made during the manufacturing process to the pump, pressure regulator, and valve body. On electronic transmissions, we make sure that all transmission programs are set to stock factory configuration. Otherwise you can overpressurize an electronic transmission, resulting in severe wear, damage, and eventually failure."

Fluid Change
Since street/strip machines take far more abuse than a typically passenger car, their transmission fluid should be changed more frequently. "All of our transmissions are dyno-tested using synthetic trans fluid and are shipped with 7-9 quarts of synthetic inside the transmission along with 4-6 quarts of the highest-quality nonsynthetic fluid," explains Farah. "This synthetic blend provides the protection of a synthetic with the viscosity of a nonsynthetic. The transmission fluid does not need to be changed for 20,000 to 25,000 miles, at which point high-quality nonsynthetic fluid should be utilized. Automatic trans fluid has detergent qualities, which are harmful to the friction material if overused."

Alphanumeric Soup
In recent years GM has revised its transmission lineup. To avoid any confusion when selecting a trans for your street machine, here's the difference between the 4L60, 4L65, 4L70, and 4L80. "The 4L60 is simply a revised version of the 700-R4 that fits behind LT-style blocks and utilizes a TV cable to control line pressure and shift points," explains Farah. "GM's later computer-controlled version was dubbed the 4L60E. The 4L65 and 4L70, which fit LS motors, are upgraded versions of the 4L60E utilizing the latest-generation planetaries for increased torque capacity. Finally, the 4L80E is essentially an electronically controlled TH400 with overdrive that is used in heavy-duty trucks from the factory."

All performance transmissions can benefit from a cooler, as heat is the number-one enemy of an automatic. Farah says that the cooler core should be mounted in front of the radiator, where it will receive direct airflow under all driving conditions. If that is not possible, then a cooler with an integrated fan can be mounted along the frame as long as it has direct airflow. "The capacity of the cooler should be as large as possible," advises Farah. "Unless you live in an extremely cold climate, we recommend at least a 20,000 GVW capacity cooler for our Level 1 and 2 packages. Our Level 3, 4, and 5 packages require a 30,000 GVW cooler due to the more aggressive driving conditions they will encounter. Optimal operating temperature for transmissions is 175 degrees F."

Gear Star