gsdog1

This is the first auto that I have ever owned. I understand the business of putting it in gear to go forward, backwards, and so on.

What I was interested in hearing about is how the different components interact together, and what each one does. Also, what happens in lock-up? The tow/haul feature is a little confusing, but hey, here to learn!

Thanks for any help, and pointers to good technical information are gratefully appreciated!

Matt

Raspy

The automatic trans can be directly compared to a manual in the fact that it has four forward gears and one reverse. However it is designed differently inside with planetary gears, clutches and bands that are actvated hydraulicly, so "shifting" is a matter of redirecting fluid under pressure.
The torque converter is the clutch. It allows the trans to be in gear, at a stop, with the engine running. Visualze two electric room fans pointing at each other. If you turn one on the other one spins too. The engine is connected to one and the trans to the other. When the engine revs up the second fan drives the truck through the trans. Both fans are in a casing filled with oil, the torque converter. This is greatly simplified but gives the idea.
"Lockup" means the two fans are connected together with a clutch, a "lockup clutch". This stops all slipping in the torque converter which means less heat and greater efficiency as well as, in effect, another gear ratio. It's that last little slowing of the engine you feel as the trans makes its final shift. Also, after it's locked, when you ask for more power the tack does not rise faster than the speedo. Without lockup, when you step on the throttle, you can see the tack jump up a few hundred RPM. The trans cannot be in lockup at a stop with the truck in gear, just as you cannot stop in a manual trans truck while it is in gear with the clutch engaged, without killing the engine.
The torque converter also has another purpose and that is torque multiplication. It helps starting out with heavy loads by multiplying the torque to the trans and acting as a lower gear.
All of this shifting is controlled electronicly based on engine speed, and load. And carried out through hydraulic pressure, routed in the tranny, by the valve body.
Tow/Haul is just different programming to, among other things, allow the tranny to lockup in lower gears and keep it out of overdrive for heavy pulling.

Wetspirit

sbutter

Take a look at this

There is also a link in that article for one about stall speeds. Also worth understanding.

-Sam