I have a 1995 FJ80, mostly stock. 268K miles. When decelerating without using the brakes, basically using engine braking, at speeds over 50 mph the truck vibrates as if running over a rumble strip, until the speed drops below 50 mph. It only happens in Drive and Overdrive, and gets worse at higher speeds. It does not happen in second gear, or when I put the transmission in neutral. If I coast in neutral, with the engine rpm dropped to about 1000, it briefly vibrates when I put the transmission back in Drive and the rpm comes back up. It almost seems like the engine speed and wheel speed are mismatched. Has anyone experienced this?