Wont shift

What led you to the throttle position sensor for a transmission problem? It's time for a diagnosis from a transmission specialty shop. If you have the computer-controlled transmission, they will start by reading any stored diagnostic fault codes. If you have the older hydraulically-controlled transmission, they may need to perform a series of pressure tests to determine why it isn't shifting.

The inability to increase engine speed over 1500 rpm should not be related to transmission problems. There might be something in common you're not seeing such as a plugged catalytic converter or dragging brakes.

Hmmm. It's true, the throttle position sensor can affect shifting, but mainly on the diesel engines with electronic throttle controls. On gas engines he actually has very little say in how much fuel enters the engine. Is it possible the transmission is not up-shifting in response to your having to push the gas pedal further than normal, and the real problem is just lack of acceleration?

Throttle body assemblies on Chrysler products hardly ever go bad. Your friend is going to have to be more specific than just "junk". Tell him that doesn't mean much. The only problem I've ever seen is worn throttle shaft bushings that allow air to sneak in past them. That will cause an increase in idle speed and possible surging.

Given your description, I think I would suspect a plugged catalytic converter first. There is a gauge mechanics use to measure the back pressure in the exhaust system. What you can check on your own is a plugged converter usually causes the engine to idle uncommonly smoothly and you will hear more of a hiss from the tail pipe instead of the normal "putt putt". It will sound similar to when you hold the bottom of your shoe over the end of the tail pipe.

Holler back after you try the throttle body. If that solves it I'd sure like to know what was wrong with it.