Purpose and operating principle of the valve body
The hydraulic block, or hydraulic distributor, receiving signals from the electronic control unit, switches the channels in the control valve block and controls the clutch engagement pressure.
Depending on the signal, one or another solenoid is actuated, and the fluid, passing through the distributor channels, acts on the corresponding clutch mechanism.
We examined the removal of the hydraulic distributor in the article — “Dismantling the DPO (AL4) automatic gearbox”.
Composition of the hydraulic distributor
The hydraulic distributor (fig. 1) consists of the upper and lower solenoid valve housings, separator plates, gaskets, the pressure control solenoid valve, the torque converter lock-up solenoid valve and the sequential gearshift solenoid valves.
General repair instructions
The repair of the valve body consists in replacing worn valves, the seals on the solenoids and washing the valve body.
When working with the control valve housing, be especially careful, as it consists of a large number of precision parts.
When removing, arrange the parts in a certain order so as not to confuse them.
Clean the removed parts with solvent and dry them with compressed air. Blow through all the holes and channels with compressed air.
Dismantling the valve body
Removing the lower and upper covers
After removing the distribution block, we disconnect the wiring harness from the valves (fig. 2).
We unscrew the ten screws fastening the lower cover of the block (fig. 3) and remove it.
We extract the control rod (fig. 4).
We turn the valve body over, unscrew the seven screws of the upper cover of the block (fig. 5) and remove it.
Removing the valves and housings
We extract the pressure control solenoid valve 1 (fig. 6) and the torque converter lock-up solenoid valve 2.
We remove the upper housing of the control valves (fig. 7).
We remove the plate separator (fig. 8).
Removing the solenoids and rods
We unscrew the screws fastening the solenoids and extract the solenoids (fig. 9).
We extract the rods and springs (fig. 10).
Washing and assembly
After dismantling, the block and all parts of the hydraulic distributor are washed. The seals and defective parts are replaced.
We assemble the block in the reverse order.
Materials and tools used
- Solvent — for cleaning the removed parts of the valve body.
- Compressed air — for drying the parts and blowing through the holes and channels.
- Screwdriver set (including Phillips) — for unscrewing the screws of the lower and upper covers and the solenoid fastenings.
- Containers for laying out the parts — to maintain order during dismantling (precision and similar parts).
- New solenoid seals — mandatory replacement during repair.
- New valves (in case of wear) — replacement of worn valve body valves.
- Clean lint-free cloth or wipes — for wiping the parts (do not use fluffy materials so as not to block the channels).