HELP!! I just got a 2003 dodge neon sxt with 153,000 miles on it. I've been driving it only a month and i have noticed when i drive uphill or when it gets to 40 mph it starts slipping or a pulling feeling like it doesnt have the power unless you give it more gas. And it the same goes for when i stop at a stop light or stop sign etc. when i change the gears from drive, park, neutral, reverse, it makes a thud sound too. it hasnt done this before so i am unsure of whats going on since this is my first car =/

 

have you checked the tranny fluid? see if its full or needs a fill and check the color and texture and smell it, does it smell burnt, does it look creamy or sludgish? another thing to remember not saying you dont know this but check the tranny when its running, im guessing you have a automatic cause you said you can put it in park, i've never owned a neon with a auto but i have a few friends that have, and one of them his tranny went out around 150k miles and the other had antifreeze get into "somthing broke or blew and aloud anti-freeze to seep into the tranny"