I know this subject has been discussed a ton, and I have been researching for a week now but haven't found a solution yet.
I have a 2003 CTD with 48re tranny. Tranny shifts great 1-3, but most often it will not shift into 4th or 4th lock up. I have a bd torque lock and with the switch on, tranny will shift through all 4 gears and holds 4th lock up. I took truck to tranny shop where they did a flush, band adjustment, and installed a noise filter at the ECM. This did not fix the issue. Shop said tranny pan looked great and clean. It has a new Gov solenoid, and the other one was replaced as well (forgot name). I checked and cleaned all grounds and added BW grease. Cleaned and greased all ECM plugs. I have no clue where to look and what to try next. Also, not sure if this is related, but cruise control will not set. Cruise light comes on, but wont set. I just bought this truck and it has only 105K miles. Any thoughts?

 

lock up solenoid and transducer were replaced? I had this issue turned out to be the internal wiring harness! It would blow the transducer!

 

read from mopar man's website that a bad diode in your alternator can cause misc ac electric "noise" to screw with your lock up solonoid

 

Any codes? check here.
Mopar1973Man's Dodge Cummins Articles - 3rd Generation Common Rail

 

Ok, Kind of noticed something strange. Like I said, no engine codes, and it shifts fine and into lock up with BD Torque Lock engaged. I noticed that if I feather the throttle, like barely anything, It will shift through all 4 gears, and eventually hit lock up around 40 but shift back to 3rd around 50 MPH.. If I give it some good throttle, it will stay in 3rd clear up to 3,000 rpm and 70 MPH Never wanting to shift into 4th gear. Is this a APPS Issue or some sort of speed sensor issue? Also, I found an Edge Juice with attitude programmer with monitor locally for sale for $400. Would this programmer help shifting? Is this programmer any good to have?

 

I noticed this morning that as I light throttled the truck it did shift into 4th and lock up. I set cruise controll and everything worked until I turned cruise off. It then downshift ed into 3rd and never went back into 4th. This was on the freeway doing 65. Anyone have any pointers for me?

 

Dangerous 1965, if the transducer was blown, wouldn't that prevent all 4th gear shifts and lock up? I'm pretty stumped here... Anyone wanna chime in? It has to be an issue preventing 4th gear shift, lock up, and cruise controll function. Like I said, cruise worked this morning along with it shifting correct with a light pedal. When no 4th gear I also can't use cruise control. What tells both of these to work?

 

Ecm uses speed sensor and RPm's Maybe your speed sensor is bad?? It's cheap and on the tranny!

 

Total newbie to 24v's and only had mine a couple months.. But I had a problem with my old 91 not shifting into 4th or shifting into 4th just to go back into 3rd. My problem was a (TPS) Throttle Position Sensor. I don't even know if our trucks have a TPS haha but the story sounded similar to my problem so figured I'd give my 2cents. Hope ya get it taken care of.