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Torque convert operation explanation?


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Alright i've seen people speak of "locking up" and how when the torque convert is left unlocked it generates heat? can somebody explain to me how a torque converter works in laymens terms lol

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Explaining how a torque converter works is easy and hard, and best done if you work on them or have had one apart, they work on oil friction, or oil as a replacement of friction I guess. I never really understood them until I got to see one apart. I work on much larger fluid couplings than your average vehicle torque converter though.

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Alright i've seen people speak of "locking up" and how when the torque convert is left unlocked it generates heat? can somebody explain to me how a torque converter works in laymens terms lol

 

Ok, I'll take a stab at this too. In its simplest terms, picture two typical box fans that turned off and facing each other. If you turn one of them on, the air that is blown toward the other will turn the fan blades of the fan that is turned off. Now, replace that air with fluid and connect the the input or "turbine" shaft of the transmission to the second fan and we can start to get the idea.

 

We can use a larger Allison transmission as an example too. The torque converter assembly consists of some basic parts:

 

Cover

Stator

Lock-up dampener

Turbine

Pump

 

The cover will have the mechanism that attaches to the engine (flex plate) and turns at engine speed.

The TC pump is bolted directly to the cover and has the tangs that turn the charging pump. As such, it turns at engine speed too.

The turbine is sandwiched between the pump and the cover with a thrust bearing on both sides of it. It is splined to fit the turbine shaft (input shaft) of the transmission.

I can't comment on the stator (proprietary information)

The lockup dampener (clutch) lives in the cover and is splined to the turbine. When the the clutch is not applied, the dampener is in a constant state of slippage. When the clutch is engaged, it locks the turbine directly with the cover which is turning at engine speed and gives a direct connection to the turbine shaft. Since it is slippage that causes heat and inefficiency, it's good to get that lockup clutched engaged as soon as the vehicle speed is high enough and the engine is in its torque range.

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I'll add a bit more to the above description. The fan analogy is good, but I think of it as a fluid gear for simplicity. The greater the "slippage" between the engine output and transmission input shafts, the greater the torque amplification (like a gear), but more energy gets lost as heat in the fluid too. As speed increases, the input/output shafts come closer in rpm, and torque amplification & heat generation rolls off. Once the input and output shafts are turning at similar speeds, you gain efficiency by locking them into synchronous rotation. The TC clutch is engaged electronically by the TCM, and is only allowed below a specified throttle% vs speed for each gear.

 

A TC lockup clutch didn't exist in older auto transmissions, but were added later to increase efficiency. A major "driver" for developing newer 6-spd and 8-spd autos was to reduce the use of a TC (fluid) for generating torque. A steeper 1st uses the TC less to get going, and tighter gear steps benefits less from TC torque amplification. Multiple cruising gears help with hwy efficiency too. I haven't studied the 6L80 shift patterns, but I think they lock the TC from 4th through 6th (stock programming), whereas GM allows 3rd/4th to lock on the 4L60.

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i have no GM access for awhile or it would have been the real decript and operation for you my friend and Michell on demand sucks ass

 

so i googled it lol

 

 

Here, I had some extra punctuation marks on my desk, you're welcome to use them sometime!

[......,,,,,,......:;;:;!!!!!!?????????.......,,,,,]

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i have no GM access for awhile or it would have been the real decript and operation for you my friend and Michell on demand sucks ass

 

so i googled it lol

 

 

 

 

Here, I had some extra punctuation marks on my desk, you're welcome to use them sometime!

[......,,,,,,......:;;:;!!!!!!?????????.......,,,,,]

 

 

 

did i make a mistake or sumfin ?

 

i think i must have . sorry Mike.

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i have no GM access for awhile or it would have been the real decript and operation for you my friend and Michell on demand sucks ass

 

so i googled it lol

 

 

 

 

Here, I had some extra punctuation marks on my desk, you're welcome to use them sometime!

[......,,,,,,......:;;:;!!!!!!?????????.......,,,,,]

 

 

 

did i make a mistake or sumfin ?

 

i think i must have . sorry Mike.

 

 

No, just giving you a hard time.

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i have no GM access for awhile or it would have been the real decript and operation for you my friend and Michell on demand sucks ass

 

so i googled it lol

 

 

 

 

Here, I had some extra punctuation marks on my desk, you're welcome to use them sometime!

[......,,,,,,......:;;:;!!!!!!?????????.......,,,,,]

 

 

 

did i make a mistake or sumfin ?

 

i think i must have . sorry Mike.

 

 

No, just giving you a hard time.

 

 

oh,

 

haha

 

i get it ,,,

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To see how a torque converter works, take a look at this pdf...

 

http://www.autoshop101.com/forms/AT02.pdf

 

I think Chrysler was the first of the big three to have lock up TC's. They were hydraulically engaged, no electric solenoids. When the first cars came out with them (78 I believe) they had issues with the lockup. They had a spring holding the spool valve back. The first bunch had issues with the spool valve, and when the lockup occured, it would not supply enough pressure to apply the clutch completely. This would cause the complete dash assembly to bounce up and down while the converter would just chatter like a clutch that had oil on it. The dash would move 2 to 3 inches up and down.

 

For fun, I would play with the valve body to get the lockup happen in 1st or 2nd gear, and stay locked up through the shifts. Even a 6 cylinder Volare would bark the tires on the 1-2 shift.

 

I know this is getting off topic, but this thread brought back memories of the 904 and 727 transmissions

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Somebody told me that when towing you DON'T want the torque converter constantly locking/unlocking because THAT causes heat (the lock, unlock). You guy are saying that running with the TC unlocked can cause excess heat?

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Locking and unlocking the TC does not create any heat. Heat is generated whenever there is fluid slip in the TC which only occurs when the TC in unlocked.

 

DEWFPO

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