I recently purchased a 1997 F150 with a 4.6V8 and 4 spd auto. The torque converter will not lock up until the truck is fully warmed up. Sometimes this takes 10 miles or more. Is this normal? (I should note that it is below freezing here.) Once it warms up, everything works okay. Also, I noticed when cold the fluid level barely registers on the end of the dipstick. When warm it is in the middle of the cross hatched area. Should I add more fluid? Lastly, is it normal for the converter to unlock when I let off the gas and then rev up and relock when I give it more? Other than this driving me crazy, I love the truck! Just wish it would find a gear and stay in it.

 

Everything you're describing is normal.

-The TC will not lock until the engine and transmission fluid reach a certain temperature.

-The fluid should only be checked when warm. Ford issued a TSB a few years ago about this because dealers were checking the fluid on newly delivered vehicles, noticing just as you did that it seems low when cold, and adding more. When warm, it should be within the cross marks.

-The TC will unlock when you let your foot off the gas. This allows for engine braking in 4th gear. It won't lock again until you apply gas.

 

Creepy but true. You can do some OD tweeks with a chip or tuner.