How Does a Powershift Transmission Work?by John Albers
A powershift transmission is a new type of manual transmission developed by Volvo to allow for safer powershifting. Powershifting is a process by which a driver can get more power out of their engine by keeping the accelerator pedal depressed while engaging the clutch pedal and shifting gears. There is a significant downside to this process. It causes excessive wear to both the entire clutch assembly as well as the transmission. The powershift transmission is specifically designed to allow for powershifting without damaging the vehicle.
The powershift transmission looks much like a normal transmission from the outside. It connects the engine to the driveshaft, which connects to the vehicle's drive axle. Inside is a camshaft which, depending on the position of the stick shifter set between the passenger and driver side floor, aligns a different set of gears to allow for different gear ratios. It's these gear ratios which translate the generally constant rate of power coming from the engine into various turning speeds for the vehicle's wheels. Unlike a traditional manual transmission, the powershift transmission has two camshafts and two separate sets of gears. One camshaft is nestled inside the other, controlling the odd numbered gears, while the other controls the even numbered gear settings.
The powershift transmission starts in first gear with one specific set of gears turning against the camshaft. Unlike traditional transmissions, the other camshaft is already set and hovering over the gears which would be used when the vehicle upshifts. This way the accelerator need not be released when shifting to avoid the gears binding and damaging one another. When the clutch pedal is depressed, and the stick shift manipulated to upshift, the next gear setting is already in place and waiting. All upshifting does is cause the first camshaft to leap frog to the next gear in sequence. Thus, when the clutch pedal is released, the second camshaft engages in the second gear set, this time with the original camshaft waiting over the third gear setting. The process continues until the vehicle is at the highest gear setting, and repeats once it's returned to first gear.