Can anyone help this guy?

Shaners · January 20, 2002

This new forum member has a '65 truck with a '97 drivetrain and he has problems with OD in his auto tranny. Please check out this thread,

thanks

OD problems

tfpary · January 20, 2002

??? I just quickly scanned through the thread. I think you might want to focus on what conditions the computer "normally" unlocks the torque convertor. Wait a minute - you said overdrive... do you mean 4th gear or convertor lock up. I guess I better reread the thread.. but my original idea still applies. Find out what causes the electronics to prevent the transmission or torque convertor from shifting or locking.... in other words, if the truck is running correctly, under what conditions would the transmission not shift to 4th? Temp? doubtful... Load? How does it determine load... Vacuum? engine speed versus road speed? If it seems like i am guessing I am. Just trying to give you some ideas.

tfpary · January 20, 2002

:stupid: I reread your original post... Now I see that it wont stay in 4th when throttle is applied correct? What conditions does the pcm see that forces it to downshift? throttle postion? throttle postion vs road speed? I dont know... Could be a sensor that the pcm uses to determine the shifting is on the way out. Another possibility is as the truck warms up it loses these types of inputs, as you mentioned the computer can't be accessed by a code reader, but I would think that the truck would be fully warmed up long before 40 minutes. If I were you, I would try to get a set of service manuals for the 97 model year. Try ebay for a cheap one, or your local library.

turbofrank · January 20, 2002

I would look at the vehicle speed sensor first, if there even is one. Also check and make sure the computer is seeing the proper temp. If it thinks the engine is too cold it won't shift into OD.