[Edahall]

The 700R4 is definitely very weak in overdrive and even more so behind a diesel engine that puts out lots of torque at low rpm's. It was never designed for heavy pulling in that gear. If the engine is racing in direct drive (3rd gear), it's better to select a different axle ratio that drops the rpm's to a respectable level than to tow in overdrive. My 1982 diesel Suburban with 3.08's is happy at 1900 rpm's in direct drive towing at 60 mph. On the hills, I simply downshift to 2nd gear. Overdrive is only used for solo driving and I can go as fast as I want in that gear.