Bought my first lx470. Love the vehicle and I bought it site un seen. 2006, 96k miles, great condition. However, every now and then when accelerating from a stop, there's a thump, bump, bang...whatever you want to call it from the rear end or the tranny. Just trying to figure out if this is a normal thing in a LX or should I get it looked at? I have only enjoyed GM vehicles until now. TIA.