What does "lock up" mean with regard to a transmission?

I asked someone about safe transmission temperatures and he responded like this:

".....pulling up a hill when the converter is not locked up...."

and

"....enough power to pull in overdrive in lock up...."

What the heck does he mean.

 

Theres a clutch in the T.Q. and it is controled electricaly and that is overdrive when the T.Q. is looked up , some trucks have a botton on the dash that lets you have some control of the T.Q. and thats for some driving conditions , I like it best for if your rite at the speed that the tq con wants to go in and out [ 40-45] , thats hard on the trans. so I hit the button to keep it from looking up when your stuck behind trafic and can not go faster.

 

You can tell when the TC is locked up because you can feel it lock up (4 th gear shift) and when you step on the throttle the tach is slow to respond. The TC is locked up and not its direct drive, no slipping.

 

Thanks, guys. It wasn't as complicated as I thought. I appreciate the information.

 

No problem, ask away. If I don't know the answer I'll just BS until you believe me!