A piggyback pulley is not necessary on our Fox's. It's a term used usually when describing aftermarket pulleys for a '96-up 4.6L.
The “piggyback” refers to an additional pulley that bolts directly to the "Dampener" (not “Harmonic Balancer” like our 5.0L, as a 4.6L is internally balanced) instead of the pulley and dampener being of all one piece. Hence the term used “Piggyback”……One on top of the other. It's just a less expensive way of under driving the pulleys on the 4.6L versus buying a whole new dampener.
