I just put new gears in my 2002 150..I already had the 6 inch kit and 35's but now put 4:56 gears in it...does it need to be reprogrammed? What needs to be done..?

 

You need to get a programmer with either canned tunes or custom tunes (preferred) and adjust the tire size and gear ratio.

Check out the Chips, Tuners, and Programming forum (the first one on top) and pay particular attention to the sticky threads.