Project LBZ Part 2

ATS Stage 7 Allison Transmission Kit

The Stage 7 Allison Transmission kit from ATS came with everything needed to reinforce the transmission and to handle the extra power of the truck. Transmissions are one of the most common failure points of a modified truck. As the horsepower and torque output increase, the clutch plate materials begin to burn and slip, causing the transmission to fail. In order to prevent such failures the Stage 7 transmission kit comes with three distinct major changes over stock.

“Starting with the clutches: the clutches in all of our Allison rebuild kits, including the Stage 7 kit on Project LBZ, covers clutches one through five,” says Ryan Gelinas, extramural purchasing consultant at ATS Diesel Performance. “All of the clutches are ATS clutches in the kit. We actually have a laser table and we cut all of our own steels and we die punch out all the compression materials and bond them at ATS. We don’t use another company’s clutch; we use our own clutches for all of our rebuild kits.”

The clutch material itself is something ATS had specially formulated. It’s a good mix of cellulose and Kevlar. Cellulose is great for traction, but it tends to burn. Kevlar will not burn up, but it has terrible traction. At ATS it’s all about finding a good, happy balance between what handles the torque and the horsepower of the diesel.

“It’s the same clutches that we use in our torque converters, as well,” adds Gelinas. “The billet converter in that kit is a triple lock converter. It has a billet cover, a billet stator and billet apply piston.”

The way an Allison works is that it has a pump that runs at 300 psi. It’s always pumping no matter what; it doesn’t have a mechanical throttle valve and is electronically controlled with a trim valve solenoid. As a clutch pack needs line pressure, the trim valve lets part of the 300 psi in.

“Our Valve body comes with an additional solenoid that the co-pilot hooks into and it can actually put full line pressure to the clutch pack,” says Gelinas. “In stock, you’ll only get about 90 to 110 psi line pressure with the way the trim valves are set up. The co-pilot comes with a Stage 7 kit and is dynamic—it actually follows the engine load, which is boost and throttle percentage.”

It calculates your estimated horsepower and applies the right amount of line pressure, so the pump and solenoids don’t wear out. It is also engaging and disengaging the torque converter clutch based on whether or not you make your power.

“If you’re not heavy into the throttle and you are at low boost, it’s going to keep you locked up as you are tooling about town, but as soon as you tip back into the throttle, it notices more throttle when it doesn’t see enough boost and it will unlock your converter and get you on top of the boost to keep from bogging down the truck,” adds Gelinas. “Unlike the stock TCM calibration, the co-pilot will keep the converter clutch engaged under wide open throttle to really put the power to the ground.”