[chiphead]

A harsh shift shocks the internal parts and can cause breakage. The main line pressure, accumulators, orifice sizes in the separator plate, check balls, waved apply plates, clutch pack clearance, clutch spring number and type, type of frictions and steels, type of fluid, torque converter efficiency all works together to determine shift firmness and timing.

The B&M kits are known to be very aggressive, using large plate sizes and high pressure springs along with disabling the accumulators and removing flow check balls. This results in the super fast and hard "bang-chirp" type shifts that tend to break things.