2001 ram 4x4 down shift issue

Helping a neighbor out here, he has a 2001 dodge ram. While driving with the cruise at about 60 miles per hour and pulling a moderate hill it down shifted out of o/d into 3rd then quickly down to 2nd and would not up shift again until engine was restarted. a few days later it would not shift from 2nd to 3rd unless engine was restarted. No check engine light, nor any codes with code reader. any ideals would be appreciated. :confused:

This is gonna sound odd but I've read of stray voltages from bad alternators messing with the transmission signals.
Set your digital volt/ohm meter to read AC millivolts then with the engine running, probe the battery terminals. If you don't have one, check with the local chain type auto parts store for one to borrow.
Acceptable AC volts are .2 to .3.