My van will not go faster than 30mph, why? on 1996 Dodge Ram Van 2500

I was driving and the van wanted to up-shift (like it was going up hill). Now I can't get it to go any faster than 30mph, it will shift fine. When you start it, it sounds fine, but when you step on the gas pedal, it sounds horrible. What's going on?

Asked by for the 1996 Dodge Ram Van 2500
seek a free diag at aamco the shop pricing
1 more answer
it could be a number of things such as a plugged fuel filter or catalytic converter or a bad tranny