On my 02 2500 I had to replace my overdrive unit. It's all back together now, change tranny filter and fluid. Now driving down the road the truck stays and I'm guessing 1st gear. Check the connectors they are good. Tried disconnecting relay and fuse doing manual shifting nothing. Checked the output shaft sensor that is good 1200 ohms. Put up on jack stands and ran still do not want to shift also checked kickdown cable and spring looks good. As I had the truck up there I ran it and if I shifted from 2nd gear down to First I would feel a change like it was dropping on the 1st but I'm not sure if it actually was. I don't know if you guys think it might be the pressure solenoid or sensor, I also adjust the Bands while I was in the pan. Just trying to get your guys opinions please help

 

I just had an issue not shifting into 4th with my 48re- I hope you have better luck than me- recommended to do the pressure solenoid and transducer for ANY gears since that is where the cycle/shifting starts. I would use a clean bucket and save what fluid is in there to re-add. Depending on miles on your trans the new ATF will break down gunk and clog the solenoid/transducer. I would pull output sensor and wipe it clean real quick to cover your bases or buy a new one for $20. Easy install on all parts. I got my parts at a local transstar for about $100 here in TX (Borg Warner gov pressure solenoid, transducer, output shaft sensor)

 

Yeah I had one trans shop tell me it's junk. The fluid was flushed 6months prior to this happening. Shifted fine after. I did check the outside band which was loose and I got a 1-2 shift. Took to another shop and he said do the governor and sensors which I will do. I will be upgrading the transducer also