My trans won't lock the converter until 70 mph with the throttle floored, and won't shift into OD until 75 or sometimes 80. Sometimes if I let out of the throttle as soon as the converter locks, it will shift into OD. OD button will immediately take it out of OD, but won't go into OD again until above procedure is repeated. As for downshifting, will only downshift out of OD with the aforementioned button, or by pressing the throttle to the floor. If I coast to a stop, converter will not unlock, and trans will not downshift. If driving in 3rd with converter locked, the only way to unlock it is to shut off the truck and restart. I have done extensive searching on the subject, and am leaning towards the governor pressure solenoid, transducer, or both. Truck has 225 K, but the trans has about 90K. Completely stock trans, no boxes or other gadgetry (?sp.) Fluid level fine, all fluids changed on a regular basis.

 

have you checked for codes?

 

no codes found...also an update...unhooked my trailer to head home, won't lock or shift into 4th at all now, not willing to do 85 to try either