Lately whan I give my F-250 4x4 gas to pass or get a little heavy in the pedal. I see the rpm's stay at about 2500 but it feels like the truck isn't getting any power. I've done some heavy towing in the past but nothing in the last few months. Am I looking at a trans rebuild, or is there somthing I can look at first. The truck has about 130000 miles. I bought it used about 35000 miles ago. I have done nothing but oil changes, brakes,and a new water pump in this time... Thanks in advance

 

Check fluid level and if it is ok, drop pan and see if there is debris in it.