Overdrive not working

[ferlar]

Hello everyone. My 1988 extended cab with a 2.9 engine and an automatic transmission is doing great. I use it everyday to go to work and continue to be very happy with it. BUT, I do have a problem; all gears shift fine except the overdrive. If anyone could suggest some steps I could take to diagnose the problem I will be very thankful.

 

[franklin2]

Your 3-4 shift solenoid is controlled by the engine computer. I would pull the codes and see if there is a problem there. I know some vehicles delay going into overdrive till they warm up and go into closed loop. If you have a problem and it's not going into closed loop, it may not let it shift into overdrive. A lot of these older vehicles will not set a check engine light if you have a code or codes.

 

[ferlar]

Thank you Franklin, I will check the codes. Over the weekend I checked the vacuum line to the transmission and replaced a broken hose but the problem remains .