I've been educating myself this morning (for no particular reason) about torque converters and I've been reading the various posts about keeping it locked while towing.

BTW, Excellent newbie info at:
http://www.howstuffworks.com/torque-converter.htm

I think I understand lockup and why you want to make sure you're in it while towing heavy stuff (to avoid overheating). I'm not entirely sure how you tell when you are in it or when you've come out of it.

It sounds like you have to be going over 45mph (in 3rd or 4th gear) and then you basically keep an eye on the tach making sure that it increases and decreases steadily with speed and doesn't go nuts - and having overdrive turned off helps to keep it locked but doesn't guarantee it.

Is that pretty much it?