What's a torque converter?

I spent several hours last night on this forum reading about transmission cooling, and the torque converter was mentioned many times.

What is it? Where is it? What does it mean to have it locked? Is it directly controllable or does one guess what it's doing based on noises and such?

Sorry for the probably stupid question - kindly tolerate a new guy learning the basics

 

It's basically a fluid coupling between your engine and transmission. It is immediately behind the engine in the bell housing, so you can't see it just poking your head under the truck.

"lock-up" it is just a condition where the output speed of the engine matches the input speed of the transmission (over drive on). With over drive off, it allows the engine to turn faster than the transmission input.

There are some good illustrations online that illustrate how it works exactly. There's one that shows two household fans facing each other, one is plugged in, the other is not. Conceptually, I think that illustration is the best. Youtube has some great explanations and illustrations too. I'll find a good link and post it.

 

Very good explanation. And the fan analogy is great - I never thought about it that way.

 

https://youtu.be/bRcDvCj_JPs?si=cAX572U-Bo_q7BJo

 

Is that why when accelerating, your engine speed may go up to 4k RPM's while the transmission is still accelerating the drivetrain (with overdrive on)?

 

https://youtu.be/96wuBq9EatI?si=_pRYEXFb9InyV6P2

 

Overdrive is just a gear that makes the output shaft spin faster than the input shaft. Our 6 speeds have 3 underdrive gears, one that's 1:1, and two overdrive gears.

The engine speeds up to 4000 rpm and beyond when it is in a gear that lets it spin that fast vs the vehicle speed and the accelerator is pushed hard enough that the computer chooses the lower gear. More rpm, lower gear, more torque multiplication. Our torque converters will have a couple hundred rpm of slip when unlocked but not 4000 rpms worth.

 

Lock up is when the lock up clutch is applied in the converter which stops the fluid coupling and makes it a direct drive just like a clutch on a manual transmission.

 

Thanks for the videos guys! I feel I learned a lot.

 

So did I. Thanks for asking the question.

 

I, Spraynard, also learned muchly. Prior to this thread I thought a torque converter was the thing that forced 3rd gen engines to puke out their big end bearings. But it's so much more than that!

Today will be a good day, methinks.