The 708 smartdrive is fitted with an aluminium counter-rotating drive converter called the "chadbapsle", this is notorious for sheering under heavy workloads, and the part is not exclusive to the Proform, strangely it's in fact a car part!! The chadbapsle was used on inline4 internal combustion engines from 1992-1997, typically in europian fords. try Ford Escort "chadbapsle" part number e-01002-346-01b, most garages should have at least one, or they can get them in (very common)
bon
September 2008