To all the Ford Guys, I need help with a Speedometer problem.

Hey guys, I'm normally a Pontiac Grand Am Forum regular, however I'm trying to help out my neighbor, he is a Ford Man. The vehicle is a 2000 Ford Explorer XLT. The problem is this, he states that when the truck is cold the speedo is inoperative. After the truck warms up a bit the speedo pegs out at top speed, if he travels a few miles the speedo settles down and registers normal with the exception of the addition of an electrical system such as the turn signals the speedo will bounce with the flash if the dash board indicator, or if he applies the brakes the speedo will peg out to top speed. I do not know enough about the Ford technology to even venture a guess as to what the problen is. I'm trying to help him out, you see he's fighting lung cancer and he can't work on the truck himself, so I now get to learn about the Ford product when ever he has a problem. Chances are you'll see my name here in the future. I tried to post a thread in the Explorer Forum but did not get any replies after a few days. If anyone has any input I'll be more than happy to listen.

Thank you,
Hoags