Pressure and Harsh Shifting

EPC solenoids control automatic transmission line pressure.

The EPC electronic pressure regulator controls mainline pressure. Mainline pressure is the source pressure for the torque converter, valve body, and clutches and bands in an automatic transmission. As flow and pressure build from the transmission pump, the regulator regulates and exhausts excessive pressure to the sump, preventing damage to friction materials and internal components.

Sticking valves can be cleaned with a lint-free cloth.

Check the condition of the fluid while checking its level. Use a piece of paper towel or a lint-free cloth. Automatic transmission fluid should be red. Only in a few transmissions is the dye left out. Overheated transmission fluid appears dark brown or black. Contaminated fluid can cause valves like the pressure regulating valve to stick in their bores. Pieces of black particles in the fluid indicate a slipping band and clutch.