2001 Expy XLT 5.4L 110K This just started happening, as you run through the gears when it comes time to shift into overdrive there a very slight vibration that lasts maybe 2 seconds or so coming from the back of the truck, maybe the rear end?. Never happened before, I've never had any tranny trouble in the past, it's not slipping or hesitating or losing power there's just the annoying vibration. Can anyone provide any insight into this? Thanks... 
