2001 F-350 w/automatic. 7.3L. 150+K miles. Have never done anything to maintain transmission. What do you suggest? What can I do in my driveway to maintain good performance? Have had little or no issues, just think something should be done without taking it to a tranny shop.

 

Changing ATF Fluid in a E4OD and 4R100 transmission - Ford Trucks

 

What Mark said. I'm just getting to this now while dealing with a leaky gasket in the rear.