I was driving back from california.When i turned the cruise on after i let off the set button the truck started to accelerate slowly.When i pushed the resume button to bring the speed down the truck started to accelerate really fast.And when i tried to bring the speed back down again with the resume button it wouldn't slow down.I had to hit the brake pedal to get the speed to a safe mph.This happed on me twice,it never happened before.

 

I would say it probably has to do with your cruise control servo. Either that our im pretty sure the cruise on 12 valves work off of vacuum. So you might have a leak somewhere. My cruise on my 12 valve hasnt worked from day one and im still trying to figure it out.

 

Thanks for the ideas.I'll check the servo out and for any leaks.