The isn't an advantage that I know of turning off overdrive when towing. It will burn more fuel.

Overdrive and the torque converter are two different things. The converter will lock and unlock regardless of overdrive.

Overdrive is fourth gear. It is like any other gear in the transmission except that it's ratio is greater than 1:1. It isn't some magical thing, it's just another gear ratio.

The torque converter has a clutch inside that when locked makes a mechanical coupling between the engine and transmission. When it is unlocked there is a fluid coupling between the engine and transmission.

There is a lot more about how transmissions work at HowStuffWorks "How Automatic Transmissions Work"

 

OK now i sorta "get it" on torque converters and how they work.

actually the "how things work" video is sorta lame. I found a couple that make more sense. here is a good one.


It seems the lockup is controlled by the computer by reducing the pressure of fluid going into the converter allowing the lock up clutch to engage the face?of the converter.

SO, i have read where some programs you can get, will if equipped with exhaust brake, cause the TC to lock up during the exhaust braking to help slow the vehicle down so when going down hill with a load.

I also see where the more expensive TC has 2, 3 or sometime 5 clutches in them. I guess a standard f-250 from factory has 1 or maybe 2 clutches in the TC and when pulling a load you can get more slippage creating heat and wear.

What is a good HD type TC to get that will get along good with the 4R100 trans in stock form or should you be looking to upgrade trans (BT) and TC at same time.

thanks for your time.