[John]

For the SKF bearing series used on the Tremec Ford overdrive transmissions, you need a 6308 2RSNR bearing. This bearing has an inner and an outer rubber seal, thus the 2RS designation and the necessary snap ring, NR designation for retaining ring, on the outer race. You can remove the unnecessary inner seal if desired. A ZZ bearing has two metal shields, one on each side and may be more leak prone when used for the tailshaft bearing. You must use the bearing with the outer race retaining ring in the F150 OD transmission.