Are you sure the guy didn't look up the seals for the wheel bearings? That has a inner and outer seal. The tranny case seals should just have 1 part # for either the driver or passenger side. At least on my 1991 SE-R this is the case. As far as replacing the axles, if it's because they're worn, do both. If it is because one had a torn boot and is now thrashed, if the other is fine just do one axle. Dave