I just bought a 1999 ram 2500 5.9L v8, back in February of this year, it recently hit 200000 miles a month or so ago. Yesterday i was driving down a hill that I've travelled a few times before in this truck with no problems, but this time i hit a minor bump entering a small turn and the check gauges light came on then suddenly went off, it went on after hitting another bump then turned off again, the oil pressure seemed to be lower than normal so i figured it must be that I'm low on oil which i later found out was true, but then i got to the highway and everything seemed pretty normal until i hit 55mph and shifted in 5th gear/overdrive. There was no acceleration at all, every other gear was perfectly normal, i did hear something that sounded like a metal drill bit tapping or hitting against something else that's metal, I stopped and let my truck cool off for a little while visiting a friend, on my way home the oil pressure was just a tad below normal so i thought everything was ok, but when i accelerated it dropped down to where it had been before. I am taking it into the shop today but id like to know what the problem might be.

 

Possibly the oil pump pickup is getting clogged..... but, the oil pressure is going to be a separate issue from the acceleration problem.

 

I had the oil pressure dropping to zero issue on and off for years, each time it was the screen on the pickup tube getting clogged. Pain in the *** and labor intensive to drop the pan but every time for me, that was the issue. Happened more on the highway, I would have to pull over and let it sit for a few minutes then it would go away.