Exploring Automatic Transmission Valve Bodies: The Heart of Gear Shifting

Greg Vaughn

Publisher's Note: Welcome to our 18th edition of Tech Tips Tuesday on "Exploring Automatic Transmission Valve Bodies: The Heart of Gear Shifting".  We'll be re-publishing an edition of AMSOIL Tech Tips for you every Tuesday.  Click on the Blog Category "AMSOIL" to see everything published to-date.

Exploring Automatic Transmission Valve Bodies: The Heart of Gear Shifting

John Gardner: Transmissions have evolved from the two-speed Powerglide to the 8-speed to 10-speed automatic transmissions today.

Welcome to this AMSOIL Tech Tip. Well, how did that all happen? It's all about the valve bodies, my friends. It causes the shifts. What is it, and how does it work? Well, you can see it right here. It actually has a bunch of valves located in there: shift valves, modulator valves, reverse valves, manual valves, everything that's directing that fluid to different chambers to make it happen.

Here's one right here, and you can see all these passages right here, all these nooks and crannies, cause that fluid to run around and go into the transmission at different points to achieve the different shifts. We're talking about shift solenoids right here; those cause different shifts 1, 2, 3, 4. This is a pressure control solenoid. Now, all these solenoids and valves, they make the shift happen.

Now, Len, could you tell us, explain how this chart works?

Len Groom: This is how it actually happens. I think if you can understand that, you can land on the moon.

John Gardner: Absolutely, it's a complex machine, but it all starts here at the pump, and then it goes through all those passages to make the shift happen.

That's good enough, Len. But a little bit earlier, I actually measured this. This is a manual valve, and your shift's connected to it. You move it back and forth. I measured it with this Vernier caliper here, from the inside and the outline, and I have a little bit of thousand, not too much play in there. And fluid has to make those valves move. How does that happen?

Len Groom: That space that you're talking about, I mean, that's less than a sheet of paper, so there's not a lot of room for anything but the fluid. So, the fluid has to remain fluid. Um, so we're talking about detergency. We don't want to have buildup. We don't want to have varnish or any type of depositing in there, or it could create sticking.

John Gardner: Now, I see that a lot. These things get varnished up. The fluids in there too long. You might have shift problems. It may be just as simple as changing your fluid or maintaining your fluid.

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Greg Vaughn
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Vaughn Enterprises, Inc.
AMSOIL Direct Jobber
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About the Author
Greg Vaughn

Family Dealership established 1974
Vietnam War Veteran
Helicopter Mechanic, Military & Civilian
Civil Service, 1982- 2003

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