94 international 9400 rpm/acceleration issue.

I own a 94 international 9400 with a Cummins 350 n14. Just recently i started noticing that the rpm won't go any higher than 16 or 17 rpm. I can shift to a higher gear and truck will slowly pick up speed, but i can't get it to the higher 20 to 23 rpm. Any help with what might be going on will be helpful thank you

 

All the time. I started driving unloaded just pulling the trailer but decided not to continue anymore

 

It does have cruise control..o
I haven't needed it or tried it in a month or so. I just do local mountain driving

 

Yes All normal, temp, oil pressure and volts

 

Engine brake works....speedometer hasn't worked since I bought it