Principles of Valve Body Testing for Automatic Transmissions

Having an automatic transmission car is a great advantage because it offers many benefits.  To better understand how your car works, you should know the principles of valve body testing. OE manufacturers claim that automatic transmissions are controlled by the accurate flow or direction of oil over a car’s hydraulic distributor.

Replacing valves is not always financially viable especially if there are many valves to be changed. Rebuilders will know if there is a problem through valve body testing. Problems with the valve body can be addressed because reamers and aftermarket valves are widely available these days. You should only consider valve replacement if one or two has a problem.

In some situations, cleaning, reaming, and valve replacement is enough but the newer automatic transmissions are different. This is because the new generation cars tend to have problems with the solenoids and valve body. Electrolysis causes the wear and tear due to reverse polarity. Problems with the inductor bushings or bushes are also gaining much attention. Depending on the bushing material, problems may occur when the bushing becomes elasticized that leads to the slipping and dragging of the operating shaft. Oftentimes, this is mistaken as problems with the valve body. It’s a good thing that there are now replacement bushings that can solve the solenoid problem.

The Principles
Control is no longer focused on the shift solenoids because it is misleading and a bit confusing. Solenoids these days are similar to diverter valves that guide the flow of oil to the right circuit. This is also known as diverter strategy.

Valve body testing can also determine if there is a drop of release pressure. This has something to do with lockup circuits. Depending on the car model, there should be at least 4 psi difference between the apply pressure and release pressure. The variable current electro-hydraulic solenoid is now used and a closed-loop system monitors it. This will ensure that the solenoids are in the right positions. You can also check for operational integrity through the valve body machine.

Valid results from the valve body testing can be obtained when the solenoids are controlled. If the latter is not controlled, results of the test are rendered invalid. A prerequisite of valve body testing is a system that uses chopper circuit for proper control. A hydraulic operation data analysis is imperative as well to determine deficiencies.

Aside from looking for a tie up or flare in the gear shifts, there is also a need to monitor the pressure and each circuit’s charge time. There is still a need to dig deeper to see results in the valve body testing.

Valve body testing should be coupled with correct testing of other relevant issues. Those working in OE facilities usually make use of this approach. The machine used for valve body testing must be capable of providing sufficient volume and oil pressure, and operate over 100°C. Such temperature is necessary to spot faults since mostly are heat sensitive.

These are some of the things you should know about valve body testing.

Author Bio:
Blue Reach Automation is an international leader in automatic transmission shifter. The automatic transmission is controlled by an extremely accurate direction and flow of oil through the hydraulic distributor or valve body as it is often referred to by some OE manufacturers.  Correct testing of anything including valve body testing should force issues so that they are picked up during a test.