1999 Up-shift/down-shift problem
 

A 1999, Ram 2500, 5.9, 4x2, 4-speed auto. At a steady 45 mph, the transmission up-shifts and down-shifts changing the rpm’s about 300 rpm between shifts. What really makes the problem difficult to diagnose is that it is intermittent. It will exist for days at a time then disappear for weeks. Replaced the BWD speed sensor but that did not solve the problem. Any advice is appreciated!

Yep, this sounds like one of the most common issues with these VP trucks. Clean all of your battery terminals and the ground contact areas. Then also do an APPS reset. If the problem still continues, insulate (with tin foil) the ground wire that goes from the passenger side battery to the motor.

Thanks! Sounds a lot simpler and less expensive than the other possibilities I was imagining....

Most likely this is the converter clutch locking/unlocking. Electrical noise in the system.
As said, clean battery posts and check grounds.
I use the DTT noise filter.
After several years it returned and I tried everything. Then laying under it I found the passenger battery ground at the block was finger tight. Snugged it down and it is good again.

My truck did the same thing. There is a large wire connection under the fuel filter, took this apart and cleaned it with contact cleaner and this helped my problem. Also wrapped the ground wire with tinfoil. Trans shop found a wire broken in the trans wire bundle between the firewall and the tranny. After all this no more problems. Just some things to look at. LOL