Just picked up a 96 3500 Dually with a V10 automatic. The transmission shifts good but won't go into overdrive. The previous owner said he thought it was the speed sensor. I changed the sensor right behind the pan on the lower side of the transmission but it still doesn't work. Any ideas?

Hasn't there been a number of posts about the solenoids attached to the valve body causing this kind of thing?

Have you had the computer error codes down loaded at looked at yet? If not start their

OBDII codes ran. Only O2 code.

Do you mind sharing the O2 code? I'm curious if its the rearmost (aftercat) sensor

Thanks

It is always possible that the OD has been switched off with the button on the end of the shifter and the light on the dash is burned out and not displaying the condition....but what do I know, I am just an old man living in Graham, WA and pounding away on a keyboard on New Year's Eve. BTW Happy New Year....

Happy New Year to you too!

If I am remembering correctly there are several things that have to happen before the computer will allow an OD signal to be sent. Engine up to temp is one. Temp sensor and wiring ok? TPS in correct range. Speed sensor in range.

Does it feel like the torque convert is locking up at the right time? If the TC is not locking/unlocking (given that you have a lock up trans) there might be bigger issues.

Or the button is pushed to keep the OD off as was suggested earlier.

Code is P0152 2/1 is the only code that shows up. The OD switch on the dash is off and when I push the button the light comes on but the OD does not work. Feels like the converter is locking up. When it shifts into 3rd and I maintain a speed in the 50-60 mph range I can see a slight drop in RPM which I believe is the converter locking up.

Dropped the pan and changed the fluid. I took the pressure solenoid out to check the o-rings and make sure it is not restricted. I also adjusted the rear band. When I went to adjust the front band I noticed the spring on the lever to the throttle was broken. I adjusted the band and replaced the spring. Took it for a test drive and the transmission shifts good but I still have no overdrive. I checked the codes and there is no code for the transmission. If the solenoid is bad won't it throw a code? Is there any symptom of a worn overdrive clutch? Still trying to figure this out.

Overdrive and lockup solenoids rarely fail. You will need to put a pressure gauge in the OD check port at the rear of the case to verify pressure. A scan tool will also be needed to verify that the PCM is commanding OD. Without doing this you are just guessing. If it is commanding OD and you have no pressure you most likely have a bad OD piston lip seal or missing check ball in the rear support/OD piston retainer. You can drop the valve body and air check the OD piston operation. You will need to make some sort of plate to cover the rectangular supply hole on the VB side of the case with a small hole in it to apply shop air. If you look closely you can see the operation of the OD piston through the case where the park rod goes into the OD housing. If there is a problem with the OD piston seal, it can be repaired with the trans in the truck and removing just the OD housing.

Thanks for the input. I will continue to work through this as time permits.

When I went through this it turned out to be the OD piston seal. I didn't know whether it was the OD or Lockup that wasn't engaging so I installed a pair of LED's on the dash to show what the computer was telling the transmission to do. They're still there to this day. Changing that seal is pretty easy.

On the 2500/3500 Rams in 1995 (edit wrongly said 1996) here is a thermistor temperature sensor in the trans cooler line going up to the radiator. If the ATF is not up to a specified temp (147?) the pcm will not let it shift into OD.

The 1500 Rams do not have this ATF temperature sensor, although there is a plug in the wiring harness near the trans.

Looks like the cooler lines have been spliced. The upper line on the radiator looks original and goes to the cooler on the driver side of the radiator. The lower line on the radiator goes to the transmission and has been spliced in two places and the one from the cooler connection to the transmission has also been spliced. I don't see a temp sensor on either line. What line is it on and where in the line is it located? I see I can get Dorman replacement lines and one of them has a sensor on it but I would like to see if there is a sensor plug somewhere. I see a harness on the driver side of the transmission and it looks like there are 3 plugs on it. Looks like two of them are capped and a 3rd plugs into a connector but I can't tell where it goes. The speed sensors and the neutral switch have their own harness and they are all plugged in.

95 and down 47rh trans equipped trucks have the trans temp sensor mounted in the trans cooler pressure line. The 47RE trans have a governor pressure transducer/ temp sensor mounted internally to monitor trans temp.

So my 96 3500 would have the temp sensor located internally and the cooler line would not have the external sensor? I did notice that Dorman lists the inlet cooler line with or without sensor. So that being said this may not be my issue. I did not see an open connector in the area to plug the sensor into.

As suggested by "71yelladustr" its best to scan it and drive it with the scanner as you can have someone go and watch all the inputs and outputs to see just what is going on. Even better if you can data record it. I used to data record all the sensors when I had driveability type problems as it lets you look at them when you get back in the shop and dont have to try and diagnose it while driving the truck. And you can take your time to watch and see if the PCM demands OD and if the PCM tries to ground the OD solenoid. That way you can see if the PCM is asking for OD and if the PCM is grounding the OD solenoid. It will also help you tell if its an electrical or mechanical problem. Also you may want to clear that code and drive it as I got fooled once when there was an emission code in the PCM and it would not let the overdrive work until I cleared the code. Sometimes when the PCM has a certain emission code it can keep other circuits turned off if it thinks it will effect emissions. That code should not but as I said I thought the same before and found out the PCM would not ground the OD solenoid to work with certain codes. Good luck with it. Ron

All "RE" transmissions have the temp sensor (thermistor) in the wiring for the OD and LU solenoid - its inside the trans where it see trans fluid temperature. The earlier OD units had the external sensor in the front cooler line - OD is disabled when the fluid temp gets around 250-265 F. The O2 splice can cause this issue as it cause noise in the circuit. In order to get OD you have to be in 3rd gear (except 48RE); have to have a stable TPS voltage at less than WOT; warmed up but not at the disable temperature noted above; neutral safety switch has to report NO Park or Neutral position; ambient air temp above some number I cannot remember anymore (-5?); speed sensor reporting higher than 35 ( I think), and I may have forgotten some others. Try setting cruise control - if it doesn't work then look at the neutral safety switch, TPS, clock spring in the steering wheel (rarely an issue but has been a cause). To check the TPS the best way is an analog voltmeter - the swing of the needle must be smooth from closed to WOT - if the needle bounces around you will have an issue. This is reallly common on the diesels - they kill the factory TPS.

Finally got around to working on the truck. I wanted to change the fluid and filter and since I had the pan off I dropped the valve body to check things out. I took a fender washer with a vacuum hose that fit snug in the hole. I attached a blow gun on the other side of the hose. I held it tight on the OD port on the rear of the case and the OD piston did not move but I heard a gush of air in the housing. I assume the OD piston seal is bad.