This may sound stupid but:
Can someone explain to me what locking up the torque converter means?
I see them advertised to lockup at different RPMs and adding manual switches for them.
The 700R4 is not computer controlled, but when I had mine rebuilt they told me that the computer locked up the converter automatically.
What is the +/- of auto vs. manual lockup? What are the advantages of different RPMs?

Thanks

 

A locking torque converter contains a clutch mechanism (TCC) which when activated locks up the torque converter so that there is no slippage. The TCC is electrically activeted via a solenoid. In computer controlled cars it ususlly only works on the higher 2 gears. It comes on at cruising speed and, releases at idle, under acceleration, and when the brakes are used. The main purpose is increase fuel mileage. A manual switch can be used in cars that have a computer that does not support the TCC.