Engine/Transmission (1994 - 1998) Newbie Question

[CorneliusJ]

What does it mean to "lock" the torque converter and can the truck operate (drive) locked or unlocked?



I know this is a dumb question, but I'm new to diesels and torque converter "locking" issues.



Thanks,



Jim

 

[AAllen]

I have a lock- up switch in my 04. 5 and when the swiitch is in the off position the trans shifts normally, but when I turn it on usally only on the dragstrip,it makes it so the transmission shifts up but will not let it downshift and the truck feels like it has dierect drive because the tc will not slip due to the clutchs being lockedup. I was consistently running 15. 0 1/4 mile time before the transmission upgrade and dropped . 6 secs off my time with the upgrade

 

[PSchwering]

The torque converter has a clutch inside that, when applied, "Locks" the torque converter. When the torque converter is Locked, The Transmission input shaft is locked to the TC housing. This gives better economy, and Makes less heat in the transmission fluid. The downside, is if you stop your vehicle with the TC locked, it will stall the engine as well(if your brakes are good enough to do it. ) The trucks computer generally will take care of this lockup function for you, but some folks want more control over thier truck's operation, Thus the "Mystery switch" . It can be used to lock up the TC when the Computer says it should not be(I. E. in second gear, When engine braking) a switch can also be devised to prevent lockup. Also, several vendors offer "Boxes" that allow you to program when you want Lockup to happen. These cost considerably more than the Switch, but are pretty handy If you don't want to flip a switch everytime you want to stop or take off.



I hope this helps your understanding, P.

 

[CorneliusJ]

Thanks form the response.

Yes, both responses helped me to understand locking.



Thanks,



Jim

 

[RCrocker]

Fuel Milage

Does your fuel milage increase by positive lock-up with a switch ??

Doesn't seem to me as though it would make a dif as the converter is alrready locked on the highway.



Thanks

Raz

-- email address removed --

 

[PSchwering]

Rcrocker,

it makes theoretical sense that it would increase economy, but I installed a switch, & ran a tank with the TC locked as much as possible, & I did not see a Measureable increase. P.