My 2003 E-350 PSD 3.55 rear, owners manual says:
• Use when driving conditions cause excessive shifting from O/D to other gears. Examples: city traffic, hilly terrain, heavy loads, trailer towing and when engine braking is required.
Well, driving thru moderately hilly terrain (Traverse City) between 55-65 mph with OD "OFF" and 9000lb trailer in tow, I watched my trans temp crawl up to 215!
Switched OD back on, and it dropped back down to 185-190, and stayed there.
No difference at all in performance.
Good thing I installed the aftermarket trans temp gauge.
• Use when driving conditions cause excessive shifting from O/D to other gears. Examples: city traffic, hilly terrain, heavy loads, trailer towing and when engine braking is required.
Well, driving thru moderately hilly terrain (Traverse City) between 55-65 mph with OD "OFF" and 9000lb trailer in tow, I watched my trans temp crawl up to 215!
Switched OD back on, and it dropped back down to 185-190, and stayed there.
No difference at all in performance.
Good thing I installed the aftermarket trans temp gauge.