Do you have the wooden slats adjusted to where the chain will not bounce up or down when under loadIJ When I tightened this chain on the 6620 and 7700, I tension the chain then match the wooden rails to be against it, but not holding the weight of the chain. Also make sure your upper and lower sprockets are in line, as this can cause the chain and sprockets to wear quickly. Also take into consideration what hrgd's post said. Any IJ's just reply to me, later 95man