When towing I stay in OD until it hunts and shifts, then I go to OD off. I've read a couple of posts about towing in 2nd gear up steep hills and that the TC locks up in second. Please enlighten me! At what speed does the TC lock up in second? Thanks-Bill

 

I lockup in second sometimes when I need speed to clime a hill from a stop when my trailer is loaded
I have a torque converter lockup switch....as soon as I'm rolling good I flip on my switch and as soon as I hit second gear my torque converter will lock in and stay locked until I turn off my lockup switch
One thing to remember is my tranny has been modified with a valve body and a heavy duty billet torque converter to handle the extra horse power and loads I haul......I wouldn't do this with a stock tranny

 

I'm not sure about the 48RE, but the stock 47RE did not have 2nd gear lockup capability. As long as you don't have any starts on a hill like pappyman said you should be fine. The transmission easily finds 3rd gear lockup when the OD is locked out.

 

My '04 locks up at 25 mph in 2nd.