Pressure and Harsh Shifting

The EPC electronic pressure control solenoid maintains an automatic transmission’s line pressure. Line pressure is the source pressure for the torque converter, valve body, and the clutches and bands in an automatic transmission. When the exhaust port is closed flow and pressure builds from the transmission pump. The regulator lowers line pressure by exhausting excessive pressure to the sump. This rapid on/off cycle maintains line pressure and prevents damage to friction materials and internal components.

Automatic Transmission Fluid Check

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 transmission fluids are tan and have no red dye. 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 slipping band and clutch friction material.