what does a motor mount sound like when its going bad but not yet bad? i have the wierd sound that i can only explain by calling it a rattle but its more of a thudding. when the truck idles and lopes kinda hard i can hear it and feel it. its not real loud but its there. sounds more on the driver side.

 

Get your wife to sit in the tahoe with it in drive and foot on the brake, give it some gas. If it does this
VIDEO0042.mp4 video by 1slow01z71 - Photobucket
You've got a bad motor mount.

 

I had the same movement it was motor mount . and another time was un torqued mount bolts