Engine/Transmission (1998.5 - 2002) Overdrive not working ??

[Turbo Terry]

!999 120 k use overdrive a lot. I have a BD exhaust brake . Bulb ok and switch OK. Will not shift down into overdrive. Is there a fuse or sensor bad someplace that I need to check?? Thanks

 

[JLandry]

Terry,



When you say the transmission won't "shift down" into overdrive, do you mean it shifts normally in 1st through 3rd gears, but won't shift UP into 4th (overdrive)?



If so, then the 3rd to 4th gear shift solenoid may have failed. This is not uncommon.



If you decide to have it replaced, it's also a good idea to also replace the governor pressure sensor and governor pressure solenoid at the same time because they occasionally fail too. I had to replace mine at about the same mileage.



Good luck,



John L.

 

[Turbo Terry]

Sorry shifts fine normal-will not shift into 3rd gear when I push the button on the shifter wand. To keep it in 3rd gear.

 

[JLandry]

Sorry shifts fine normal-will not shift into 3rd gear when I push the button on the shifter wand. To keep it in 3rd gear.

In that case, it's probably an electrical fault somewhere.



One possibility is the OD switch on the shift lever simply may have failed. If you care to test the switch yourself, you can carefully pop it straight out from the end of the shift lever using a plastic trim tool. See the attached wiring schematic from the factory service manual.



Best regards,



John L.

 

[Turbo Terry]

I will check it later today-it seems like I should have some voltage to one side of the switch as it just shunts it to ground to make it work ??? Is this a FUSED item?? From where ? everything else works ? Is there a relay or sensor somewhere that has gone bad OR is there a problem in the transmission. It shifts fine NORMAL etc. No issues. Thanks for any help.

 

[JLandry]

I will check it later today-it seems like I should have some voltage to one side of the switch as it just shunts it to ground to make it work ???

Terry,



You are correct. With the ignition switch in the RUN position, I believe you should have ~5 volts between socket 1 at the OD switch connector and vehicle ground. Socket 2 of the connector should have continuity to vehicle ground at all times.



You can also verify the OD switch itself is working by measuring the resistance between pins 1 and 2 while you push the switch.

Is this a FUSED item?? From where ?

No and no.



It's a low voltage control circuit from the PCM (Powertrain Control Module).

Is there a relay or sensor somewhere that has gone bad OR is there a problem in the transmission. It shifts fine NORMAL etc. No issues.

There is a transmission control relay in the PDC (Power Distribution Center) which is the black plastic box under the hood on the driver's fender. However, the fact that the transmission shifts normally indicates there's nothing wrong with it. You wouldn't get overdrive in the first place if it were bad.



Logic suggests this has to be a problem with the OD switch circuit. It's either the switch, the wiring, or the PCM at fault.



See what you find at the back of the OD switch and we'll take it from there.



Regards,



John L.

 

[Turbo Terry]

Well long story short. I had bought a new switch yesterday and put it in last night in my garage-opening the door and starting it up-pushing the button on the shifter wand to get a OD light on the dash. NO GO but today while driving I tried it and it works fine BUT the light bulb is toast. It was the $20 switch. But in the process the bulb quit . I use OD a lot with my exhaust brake. Now to find that little bulb and good for another 120 k. Amazing Dodge dealer had the switch. He walked around the corner and was back in a flash. For a 13 year old truck. Thanks for all your help !!

 

[JLandry]

Glad you figured it out!



John L.