I have a problem with my overdrive on my dually. The tranny has been rebuilt a while back and I have had no problems for a long time with it. But now just recently it wont go into overdrive after I have driven it around for a while. I put the DNR potentiometer on it thinking that would fix it and it didnt. Example: I drove into town just a bit ago, its 10 miles to town, it shifted fine, even the potentiometer worked great. Parked at the store for about 30 mins or so. Started driving back home and when I got up to the OD speed, it never shifted. Nothing I did with the potentiometer would make it shift either. Its done this several times now and it always seems to happen after the transmission is warmed up.

Any ideas? Can the detent cable keep it from shifting into OD? Or anything else I can check?

 

since it seems to be heat related you could check your od connection on the drivers side of the trans, you could also check the solenoid for continuity when the problem occurs .

 

Its pretty greasy and dirty. But it seems to be plugged in good. Is the solenoid inside i guess? Just remove it and check it out that way?

 

How is your speedo working these days?

 

It seems to work fine so far. The other night I drove it and the OD worked fine in it, but I was babying it and not accelerating hard or passing anyone.

 

you have to drop the trans pan to get at the solenoid. to check the continuityall you would have to do is remove the plug and check from one pin to the other with your tester. if im wrong im sure somebody will say so.

 

unplug the sensor in the hott line coming out of the trans. Make a little jumper wire and plug a wire into each end of the plug. This will fool the computer into the thinking the trans temp switch is open. Another test would be, actually grounding out the O.d Solinoid manually. this can be done by grounding out the wire that is in front of the blue wire poking out of the trans at ur feet if you were sitting in the truck. The blue wire is hott when the key is on, the other wire controls O.d. if ur O.d doesn't work when the wire is grounded, most likely the o.d solinoid is bad. Good luck