Hi im pretty new to all this and hoping someone can help I have a 2007 5.9 cummins it has about 140,000 miles on it anda few days ago I went to pass someone on the road and I gave it some throttle the rpm were at about 3000 and they just dropped to about 2000 and hung there and wouldn't do anything until I let off of it so now any time I give it excessive throttle for more than a few seconds it dose the same thing rpms go up it will start to accelerate then it'll drop back down to about 2000 and hang until I let out of it
I'm thinking it has to do with the transmission for the last few weeks while going through town sometimes it will shift to 3rd then drop back down to 2ed then back to 3rd real quick

If anyone has any ideas please let me know thanks