TASC Force Tips: Hydraulics Fundamentals: Check Valves
while check valves are fairly simple in design and function, they can cause various shift issues and clutch failures when not working correctly.
It’s Not in the Manual
A while back one of our members called the tech line about a 2002 Toyota Sequoia that required replacement of the valve body. After the valve body was installed the vehicle had no reverse, pulled forward in neutral but drove perfectly when the selector lever was in the overdrive position.
While doing research on the Aisin AW six-speeds, I found that the Ford/Mazda (TF81-SC) manual valve and the Volvo (TF80-SC) manual valve are almost identical. Both look the same at a glance, but up close there are critical differences. I also noticed that these two valves are just about the same as an AW55-50 manual valve. All three have the same outside diameter of 0.471 inch. Even the “Z” links look the same until you lay them side by side (do not interchange the valves or the “Z” links).