I have had my 99 xj for a few years now but had to do a motor swap last winter due to a broken piston skirt but the newer motor with less than half the miles mind you also knock and at first had plenty of power and now has none in higher gears also when accelerating has a grinding gear noise or even a buzzing noise coming from the transmission area i have already checked the bolts on the flex plate and they were all tight and no cracks that i could see. trans is original with 240k. i cant find any other threads to steer me in the right direction. halp.