[josh]

ordered a new timer for model #mde8400ayw the new one has 1 more prong on it,is that a problem?

[PS Volunteer - Appguy]

Timer pins are numbered, if one left over it may for a function not used on you dryer.

[mitercut]

Model MDE8400AYW has many series numbers based on the first two numbers of your serial number. It cold be that you have the wrong timer for your serial number. If it is for a feature your dryer does not have, you may be ok, or it could be looking for a sensor you don't have in which case the timer may not function correctly. Check with a professional appliance shop as to the exact model of timer for your series.