strange noise

[ddye40]

ok so not sure if this has anything to do with it. but the other day i put my truck in 4x4 (1993 3.0 auto trans) just to engage it and make sure it still worked. well the next day my speedometer needle starts going haywire and is bouncing around all the way past 85 while im only doing around 50. and a strange kinda hissing noise came from the dash whenever it would start doing that. then on top of that, as i was driving 2 days later, my truck is making a weird kinda clicking noise that i can hear from the inside of the caband it sounds like its right under where the bed and the cab meet. it also isnt idleing like normal, it has a more choppy idle and is clicking. sorry for all the bad info. but thats all i got considering i know nothing about cars. any help is highly appreciated!

 

[MountainMike]

I wonder if something happened to your speedo gear, jut a thought.