AT 6DCT450 solenoid repair

The operation of the AT valve body depends directly on the condition of the electromechanical valves - solenoids. Each valve body solenoid is responsible for performing a specific operation when selecting the automatic transmission mode.

The solenoids task is to open and close the hydraulic fluid circulation channels ATF. The ATF pressure is transmitted to the actuators, which results in gear changes, clutch operation, torque converter locking and park / reverse / drive switching.
The valve body failure causes such problems as thumps and jerks when shifting, slipping clutch, floating speed when the driving mode is constant (constant speed). Most often, the cause of the malfunction is the failed solenoids.

For a more accurate determination of the performance of each solenoid, a special diagnostic equipment is used, which makes it possible to carry out the test in conditions which repeat operating the automatic transmission in the working car, heating the oil to 100 degrees Celsius and setting the pressure in accordance with the automatic transmission model.

The quality of the solenoid is determined by the graphs. Below are examples of graphs obtained during testing of failed solenoids.

Saw-shaped and stepped sections of the graphs are the main signs of failure of the solenoid.

The main cause of f solenoids failure is contamination of hydraulic fluid. Micro-destruction takes place with time and work of the individual components of the automatic transmission, for example, friction clutches,  and the fragments enter the oil. Part of the fragments are caught by the oil filter, the rest are circulated throughout the body of the automatic transmission including getting into the valve body and solenoids. The mixture of oil and solid particles works as an abrasive for the solenoid parts, making the valve work more difficult and eventually leads to jamming. It is the violation of the normal displacement of the solenoid core that appears on the graph in the form of sawtooth and stepped sections. Usually, when a failed solenoid is detected, replacement is recommended, in most cases it is recommended to replace the kit.

The specialists of the Maktrans company  have developed their own method of restoring the efficiency of solenoids. The essence of the method is to replace parts with signs of abrasive damage.
First of all, the solenoid opens with a special tool. Then there is a complete disassembly and inspection of the parts of the solenoid. The solenoid consists of a body, an inductor, a cylinder, a core and a cover.

The greatest damage to parts in places of friction: a pair cylinder-core. As a result, the surface of the core is scratched.

The inner surface of the cylinder is also scratched. As a result of scratches on the surfaces, the sliding of the core inside the cylinder is difficult and eventually leads to wjamming.

To solve the problem, the damaged cylinder is replaced for a new one, and the surface of the core is polished. The cylinder can be made in two versions of the material.
In the first case, it is a metal alloy that repeats the characteristics of the original. In the second - caprolon with molybdenum oxide. Caprolon has an increased wear resistance and strength characteristics, which allows to increase the service life of the restored solenoid in comparison with the original one.

After replacing the parts, the solenoid closes and retests. After that it is installed in the valve body and further - testdrive in all modes of automatic transmission.

The cost of recovery competes profitably with the purchase of new solenoids, while maintaining the quality and reliability of the work.