confused about situation
 

ok im kinda new here and to the duramax i have a 05 lly with airaid cold air edge with attitude 4 inch turbo back mbrp and egr blocker plate my truck has almost 200000 km on her now and had it almost a year i have a problem maybe someone can help me with here a few months ago i was going down the highway and everything is fine bring her home for the night and in the morning going to work i notice my truck has a strange vibrate to her about 95 to 145 km/h only when it defuels but underload its fine i changed u joints tires re balanced crawled under and check if anything was loose and i cant find nothing there is a very small if any vibrattion in the steering and a more noticeable vibration in the seat and a thunking in the floor boards did this ever happen to anyone im confused about this problem:argh::argh::scare2:

Jack up the ft end and check to see if the wheel bearings are loose. That will cause wierd vibrations.

X2 yeah I'd check them out.

i check her out and there is no play in the front end at all there is a tinny bit of play in the slip yoke only up and down i asked a few mechanics and said its normal