Just curious. Do you drop out of O/D when you drop rpm? When your EGT's get to a certain point? When you hit a certain speed? I usually drop when I hit 1500rpm(50 mph) with little load, or when my EGT's go above 1200* @ moderate loads (60-65 mph). Above 2000rpm I'll usually not drop into drive unless I'm way past 1/2 throttle, & it won't accelerate with a heavy load (above 75 mph).
What's your shift point?

 

Speed. My truck with the 48RE and 4.10 rear end will NOT down shift to drive unless I am under 58mph. It doesn't matter how much I push the pedal or how big my load is. Tow/Haul on or not. 58mph is the magic number.