I hear about people wanting to lock up the torque converter. What exactly does this do and why do they do it?

 

Because an un-locked converter slips. Thats one of its functions. Did you ever notice that your car does not stall when you come to a stop when its still in drive, yet when you give it gas, it goes? Thats half of what the torque converter does. The other half is to provide torque multiplication, but I won't go into that.

However, a slipping TC can effect gas mileage and cause excessive heat in the transmission, so when the slipping is not needed (Highway Driving) there is a clutch inside that will "lock" the converter so it does not slip. Most people don't even realize when the converter is locked and unlocked. Its only a few hundred RPM difference, depending on the stall speed and the load put on the converter.

 

hmmm...I wonder if thats one of the reasons why my trans burnt out so fast. I mean I pounded that trans to hell which probably mostly caused it to fry. But I did alot of freeway driving and open road driving adn what not. And because my VSS is broken it doesnt lock up the convertor....I wonder if that could have caused alot of damage.

 

i suspect it was the poundingthe trans to hell part that killed it. As long as the cooling system is still good the trans probably wont overheat. After all, lots of older transmissions made out fine w/o a tcc. Eliminating unnecessary heat always helps, though. Hehe... my all torque and no power engine completly roasted my tcc. Slips real bad now... guess ill be on tc #3 soon.

 

Without converter lock the box will run hotter and fail prematurely. Your VSS also controls EGR operation, you really ought to fix it.

 

So the torque converter does lock up automatically? When do you need to manually lock it up?

 

Torque conv lock is performed by a solenoid in the transmission which is controlled by the ECM. Lock occurs when the vehicle is in closed loop generally at speeds over 35 mph. Thats why the VSS is needed. Normally a bad VSS will also throw an SES light after about 15 min of driving. People sometimes want manual control of the TCC for various reasons, I would just fix your problem and leave it alone.

 

how do i know if i have lockup or not? i dont know alot about trannys. i have a TH-400, i think from 73, thats what the guy told me, but he has a history of lieing. the convertor is stock and i need to get a new one with a higher stall but am a little confused about the whole thing. any one that knows them well who would be will ing to help me out?? it would be greatly appreciated.

 

TH 400's were three speed boxes without OD and WITHOUT a locking TC.