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What exactly is a torque converter?

drumset5994

By drumset5994
in Ask A GM Technician

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drumset5994 Enthusiast

drumset5994

Posted
Posted

OK, i have been confused for years on this.

 

What exactly is the torque converter and what does it do?

 

I understand it comes into play with overdrive. I feel 4 gears, then around 45, my RPM's drop as i cruise into Overdrive. I can also feel it if i shift it in 3rd, then let it go through the gears, there's a slight RPM drop as i cruise above 50.

 

Is this the torque converter at work? Is basically it only work at highway speeds?

 

Also, what constitutes the torque converter "locking" ...is it where it softly downshifts without downshifting into 3rd? Usually i can feel it downshift going up a hill, but if i drop it from D to 3, it'll shift down harder.

HyperBuzzin Enthusiast

HyperBuzzin

Posted
Posted

Check out THIS page. That should answer your questions.

 

The torque converter is ALWAYS at work. From zero mph, to as fast as you can go.

That's what makes you go.

diehrd Enthusiast

diehrd

Posted
Posted

Easiest example of how a T/C works is this.

 

Take to house fans, point them at each other with one on and the other off, the flow of air represents the flow of fluid from the engine side of a T/C and the fan that is being moved by air flow represents the transmission side of the T/C.

 

It is pretty simple , and to obtain "Lock up" there is a clutch disk between the blades that is applied to make the engines rotations mechanically connected to the transmissions input shaft .

 

Stall speeds which T/C are rated with are determined by inner blade angles, to see this with the 2 fans take 1 fan and off set it's angle from the other one and you will notice the free wheeling fan will spin slower meaning it has a greater stall speed then when each fan sat directly in front of each other ..

pwall Senior Enthusiast

pwall

Posted
Posted

Good question Drumset5994.

I had an idea of what it did, now at least I know for sure.

drumset5994 Enthusiast

drumset5994

Posted
  • Author
Posted

Makes it very understandable..how i feel a sudden surge in downshifting without the clunk...the torque converter. Now i now how my S10's tranny was going...it would slip in highest gear till the torque converter would kick in. Sometimes slip very very bad. Makes me wonder if it was the torque converter not working right or the tranny slipping.

diehrd Enthusiast

diehrd

Posted
Posted
Makes it very understandable..how i feel a sudden surge in downshifting without the clunk...the torque converter. Now i now how my S10's tranny was going...it would slip in highest gear till the torque converter would kick in. Sometimes slip very very bad. Makes me wonder if it was the torque converter not working right or the tranny slipping.

 

 

The slipping you are talking about was the tranny, a T/C can not on it's own change its stall speed , the blade pitch in side is welded in position .

 

I can give ya all a simple transmission explanation like i did the T/C if you want to visualize how simply it also works ..

pwall Senior Enthusiast

pwall

Posted
Posted
Makes it very understandable..how i feel a sudden surge in downshifting without the clunk...the torque converter. Now i now how my S10's tranny was going...it would slip in highest gear till the torque converter would kick in. Sometimes slip very very bad. Makes me wonder if it was the torque converter not working right or the tranny slipping.

 

 

The slipping you are talking about was the tranny, a T/C can not on it's own change its stall speed , the blade pitch in side is welded in position .

 

I can give ya all a simple transmission explanation like i did the T/C if you want to visualize how simply it also works ..

 

That would be great....thanks!

GTO72HO New Member

GTO72HO

Posted
Posted
Makes it very understandable..how i feel a sudden surge in downshifting without the clunk...the torque converter. Now i now how my S10's tranny was going...it would slip in highest gear till the torque converter would kick in. Sometimes slip very very bad. Makes me wonder if it was the torque converter not working right or the tranny slipping.

 

 

The slipping you are talking about was the tranny, a T/C can not on it's own change its stall speed , the blade pitch in side is welded in position .

 

I can give ya all a simple transmission explanation like i did the T/C if you want to visualize how simply it also works ..

 

diehrd Enthusiast

diehrd

Posted
Posted

Well here goes , I have to guess but most if not all here understand how a break caliper works ? Very basic you apply a piston which pushes fluid down a line to a second piston which in turn pushes against the break pads .

 

A transmission works exactly like a hydraulic break system.

 

The pump which is driven by the torqe converter acts like your foot on the break pedal,,It produces the pressure the transmission needs to perform breaking actions.

 

When you place a transmission in a given gear all items not related to that gear are held in place by disk like clutches or bands which look like a belt you where around your waist.

 

The clutch pack , OR band is applied by a piston just like a caliper piston applies your breaks. When a gear change takes affect what you are feeling is the application of these pistons applying force to bring a moving part to a stop. When a transmission "Slips" what happens is these clutches or bands are not able to hold the rotating parts and as a result you will lose that gear. (This can happen as a result of a bad seal on the piston, a stuck valve or because teh friction material the bands and clutches are coated with has worn off.

 

It is a tad more complicated in its controls with in the valve body but simple as well in that the pumps pressure increases with speed and as it does springs are compressed moving a valve which "Reroutes" the oil to the next gear's piston. Modern Transmissions use electric sensors which trigger a electrically controlled valve to open or close,,same principle as spring pressure but technically more efficient .

 

Basically it is a gear set connected and controlled by a hydraulic breaking system ! !

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