I have a clunk in the floorboard when shifting under light acceleration in 1st through 3rd gears that only start after the car warms up. I have ruled out u joints, crossmember, and front suspension. Now im thinking it may be internal, either the bearing retainer ir clutch fork. However, it doesnt happen when first starting out, only after about 5 mins of driving. Could this be internal? If so, what could it be? Any opinions are appreciated