When I am going over 40 mph and I just let off the gas, no brakes, the trucks seems to vibrate. It is very noticable and happens all the time when slowing, and usually happens around 40-45 mph. It only lasts a few seconds, until the speed drops under 40mph. I thought I remembered hearing about a motor mount problem, but I'm not 100% sure. I'll have it in for service next week so i wanted to get everything done at once and before the 36k warranty runs out.