4HP20 Solenoid Transmission parts, repair guidelines, problems, manuals

Transmission general data

Number of gears Transmission Type Drive Torque (Nm) ATF (full capacity) L ATF (change) L ATF type
4 AT FWD 330 8,3 3,5 LT 71141
Part type (1) Expand

Technical issues and repair guidelines

It is recommended to change fluid (Esso LT 71141) in this transmission after covering 60-80 thousand kilometers, depending on the driving style aggressiveness and transmission wear-out. The fluid level usually causes no problems, it is changed by means of partial change in several stages or complete change. The operation with insignificant fluid underfilling is also allowed, but the fluid overflow may be harmful for this transmission.

Typical problems with 4HP20:

The torque converter of the 4HP20 unit is the first component that cannot endure intensive exploitation. Initial vibrations caused by unevenly worn-out lock-up clutch lead to vibrations on the pump shaft and leakages through the seal. The next component to get out of order is the assembled oil pump. The bushing in the pump fails, forcing car owners to pay for replacement of the whole pump unit as neither bushings nor covers are supplied separately. The seal replacement without repair of the torque converter cannot solve the problem, but only buy some time.

Typical problems in electrical components of this transmission occur early and frequently. The valve body gets clogged with dirt, shavings and wear debris of friction components. In the course of the valve body repair it is quite common that some problems may occur with solenoids which exhausted their resource.

The next parts to be replaced in the 4HP20 unit are:

- Rubber-covered pistons in package F

- Piston of package D – wears out because of overheating

- Piston of package C – overheating

- Seals and piston cups of the pump and half-axle

The torque converter may have some problems when it stays neglected: wear-out of the lock-up mechanism, intended for blocking the clutch starting from the second gear. The torque converter quickly overheats and stops operating properly because of the worn-out lock-up clutch. The abovementioned factor leads to increase in fuel consumption, oil heating and pump operation, deterioration of acceleration characteristics, rapid wear-out of seals and bushings.The torque converter repair of the 4HP20 unit is more common in repair services than regularly repaired JF506, RE5R05, AXOD-E etc. But in general, this transmission is quite reliable, and when adhering to operational rules this transmission won't cause much trouble.