I have a 2005 Dodge Neon SXT. 3 days after I purchased it (used) the the transmission went out and ever since then it seems to have had nothing but problems.
More recently I've noticed that the air conditioning is screwy. Screwy in the terms of no matter which air flow setting I put it on; face, feet, etc., it only comes out of the top vent towards the windsheild. Now, the air is cold and the speed that the air comes out at works fine it's mainly where it's coming out. When you also switch for the air to circulate inside of the car you only hear a hissing sound. I've thought that it's a punctured line somewhere but I would like to know what I'm in for before I take this to the shop.

 

Ok, the hissing sound is a vacuum leak for the vent selection, easy fix just follow the hiss and plug it back in.. as for the tranny, are you trying to describe limp mode, which is when the car has only 2nd gear no matter where you place the shifter. If so it is a speed sensor there are 2 input and output, very easy to replace as well..

 

"Limp-in" mode engages for A LOT more than a bad speed sensor.