my dodge ram cummins powered truck stays in 3rd gear will shift to 4th normally. if i put in neutral and back to 1st i can shift manually and it seems to work fine that way but when i slow down to a stop i can feel it down shift back to 1st like it should but as soon i come to a complete stop it pops itself back to 3rd. has any body experienced this any info would be greatly appreciated.

 

i dont have the CTD but im just thinking out loud here... try resetting your PCM by either pulling the fuse for it or pulling off your negative battery cable for about 2 mins... somtimes the PCM learns the way you drive and adjust and readies the truck accordingly. there is a step by step write up on how to go about doing this if you just search in the thread search tool.

Also, do any codes or the check engine light come on when you turn the key to just before it starts? if so, write those down and ask on here or go to your local autozone and have them read the codes and it will give you a jumping off point to start the repair

Most importantly, Welcome to the site! you will find lots of useful information here!
oh, and as soon s you get the chance, take some pictures of the rig and introduce yourself!