When repairing a transmission valve body, it's not always necessary. Disassembly and repair are only considered when the automatic transmission's shifting pattern is abnormal, the friction plates are severely burned, or there is a large amount of friction powder inside the valve plate.

For example, in the Lexus LS400 A341E and A342E automatic transmissions, when inspecting valve plate parts, clean the upper and lower valve plates and all control valve parts with clean kerosene or gasoline.

When inspecting the surface of the control valve core, minor scratches can be polished with metallographic sandpaper. If the control valve is stuck in the valve hole, the entire valve plate assembly should be replaced. Replace the paper gasket on the partition and all plastic valve balls. There are many precautions when repairing the valve plate, such as preventing valve cores and other parts from falling during disassembly, and avoiding inserting hard objects like wires or screwdrivers into the valve holes to prevent damage.

After cleaning, dry the parts with compressed air; do not wipe them with a cotton cloth. When assembling the valve plate, check that each control valve core moves freely. Any stuck valve cores must be removed, cleaned, and reinstalled. Do not use sealant or adhesive on the valve plate gaskets or control valve parts. When replacing the baffle gasket, ensure it is correct; if a new gasket is unavailable, a homemade one can be made using cleaning paper.

When disassembling and assembling the valve plate, detailed technical documentation is essential. If unavailable, draw a diagram and record it. Before disassembling the valve body, handle the external solenoid valve's flat wire carefully; use a homemade tool to disconnect the connector. After soaking the valve body in kerosene, remove it and place it on a workbench. Remove the connecting screws, hold the baffle plate firmly, flip it over, and copy the oil circuit baffle diagram, labeling the parts.

Clean the valve body with kerosene and carburetor cleaner, using a brush to remove grease. Inspect the valve body for cracks and deformation; the plunger should operate freely and be free of cracks. Sticky plungers can be sanded with sandpaper or toothpaste. Repair one set of plungers at a time and assemble one set at a time.

Check that the free length and diameter of the spring meet the standards. Ensure the one-way ball valve is not missing and the throttle valve damper is not installed incorrectly. Replace the seals and inspect components such as the accumulator piston. Clean and dry the partition, checking for deformation and light leakage. After soaking the gasket in ATF oil, assemble the valve body according to the steps, tightening the connecting screws in a crisscross pattern, paying attention to the screw length and tightening torque.

Additionally, regularly changing the transmission fluid can reduce valve body failures. Automatic transmission fluid should be changed every three years or 60,000 kilometers, and manual transmission fluid every 100,000 kilometers. Adjust the specific intervals based on driving conditions. In short, transmission valve body repairs require careful operation to ensure each step is performed correctly.