Hi all, 2003 3500 SRW 48re Quad cab Laramie 4x4, Same thing, 3 - 4 back and forth. I don't think mine will lock up.
I have changed tcc/lockup solenoids with harness, gov solenoid and transducer, 3-4 accumulator spring, speed sensor. After talking to the owner of DNJ Components, and doing 4th gear line pressure test, its not a transmission problem. Also I have drove with the scanner hooked up, Like Team Tailandscale said, the computer is commanding 4th and sometimes it will hold for a minute in 4th and lockup, them instantly both solenoids are shut off.
After reading the threads on here I started messing with alternator, I unhooked both wire from the back and the truck drove better, still not right. Next step for me is taking alternator in and testing the diodes. I want to also rebuild battery cables and grounds around truck.
Just wanted to chime in, a 3rd gen doing this. It is driving me crazy, Along with guys wanting 25k for these trucks with 200k miles on them. I have a 12valve with a 6speed and i love the cummins, but guys need to be realistic, they aren't made from unobtainium or anything.