Ii have a 1990 F-350 box truck with 7.3 diesel and automatic trans. Fluid level is normal. When the trans is cool it will go into reverse only if I rev the engine, and does so with a jolt. Then reverse seems normal with full power. Trouble is, once warmed up it won't engage reverse even if I rev it for an extended period. The problem has just gotten worse, with great reluctance to jerk into reverse even when cool. Truck pretty much useless.
Anybody know what is occurring here? Is it easy to fix? Would dropping the valve body and cleaning it up solve the problem? Any ideas would be welcome. Thank you.