Explain torque converter please

[Newton.R]

Just bought new 2007 SLT3500 Quad Cab with 4 speed automatic. I'm not new to the Cummins group, but not a good mechanic. I've never really understood this torque converter thing. Please explain. For example: I read in the manual that going up a steep hill select a lower gear, but try and keep the torque converter locked. How the heck can I tell if it is locked or unlocked. And what is the advantage/purpose of these conditions?

 

[CDyksman]

Just bought new 2007 SLT3500 Quad Cab with 4 speed automatic. I'm not new to the Cummins group, but not a good mechanic. I've never really understood this torque converter thing. Please explain. For example: I read in the manual that going up a steep hill select a lower gear, but try and keep the torque converter locked. How the heck can I tell if it is locked or unlocked. And what is the advantage/purpose of these conditions?

Can't tell you everything you want to know, but if you go to "Howstuffworks.com", it can tell you exactly what a torque converter is, and how it works.

 

[raksasa]

Just bought new 2007 SLT3500 Quad Cab with 4 speed automatic. I'm not new to the Cummins group, but not a good mechanic. I've never really understood this torque converter thing. Please explain. For example: I read in the manual that going up a steep hill select a lower gear, but try and keep the torque converter locked. How the heck can I tell if it is locked or unlocked. And what is the advantage/purpose of these conditions?

Try this... even has a movie.





http://auto.howstuffworks.com/torque-converter.htm

 

[ScottLewis]

Good suggestion. You can also do a search of the forums on "torque converter" and get lots of info.



In simple terms, the T/C serves as kind of a fluid clutch that allows the transmission to idle in gear and transition smoothly during gear changes, accelerating and stopping. It's like 2 fans facing each other, submerged in fluid. One attached to the engine and the other to the input shaft of the transmission. As the engine fan turns it causes the fluid to turn which in turn causes the transmission fan to turn. With locking T/Cs (not all trannys have locking T/Cs) there is a clutch between them which freewheels when unlocked and forms a solid connection when locked. When the T/C is unlocked and using the fluid as the connection, heat is generated because of what is called fluid shear. That's what causes overheating of the trans. fluid under certain conditions like pulling a steep hill. If the T/C is locked, there is no shear (slipping) thus little heat developed.



I'm far from an expert on this so if I'm wrong someone can, and will, correct me.



Dan

 

[Newton.R]

Thank You. One more question please.

Thanks for the information and references. I do understand it better now. So it's best to have the converter locked when climbing a hill with a load to keep temperatures in the transmission cooler. I'm still not sure how to tell from the drivers seat if it is locked or not. Would putting it out of overdrive and keeping it in a low gear do that? My impression is that as long as it is not trying to shift gears it will be locked. Is that correct?

 

[JApol]

The easiest way to see if your T/C is locked is to let off the skinny pedal. If your RPM's drop to idle the T/C is not locked. If it stays at about the same rpm as before then your T/C is locked.

 

[Newton.R]

The easiest way to see if your T/C is locked is to let off the skinny pedal. If your RPM's drop to idle the T/C is not locked. If it stays at about the same rpm as before then your T/C is locked.

Thanks Bubba.