General

General Powerflow Description





The 4HP18 is a four speed automatic transmission designed for cars with front wheel drive and transversely mounted engine.
The transmission incorporates a hydrokinetic torque converter with integral torsional damper and a four speed planetary transmission. The output is taken across two gearwheel pairs and a side shaft to the differential built into the gear case.

In 1st and 2nd and reverse R, power is transmitted from the engine to the transmission entirely hydraulically via the torque converter.
In 3rd, the split-torque principle is employed, i.e. about 40% of the torque is transmitted hydraulically via the turbine wheel and about 60% mechanically via the torque converter housing, torsional damper and a shaft.

In 4th, 100% of the power is transmitted mechanically.
The gear changing elements of the transmission consist of hydraulically operated plate clutches, brakes and one-way clutches.
The transmission is controlled by means of a selector lever.
Gear changing takes place hydraulically, depending on accelerator pedal position and road speed.