changing rear axle bearings on a 9"

If you pull the axles, I would go ahead and change them. Unless you know how many miles are on them.

Trust me, it cost me a night in a hotel because I did not change them

If the bearing feel smooth, leave em be. Some of the newer bearings are crap. I've had as many new ones go bad as old ones. Clean the backing plates with carb cleaner and rags, then paint em.

Being that the rear end is as old as it is, you have no way of knowing how old the axle bearings are [could be original --who knows?], or truely what condition they are in.

I've changed plenty of axle bearings and never had any premature failures with Timken bearings.

If the axle bearing spins freely, it's bad. It should have enough resistance [drag] that it shouldn't make more than 1½ revolutions if you were to place your thumb against the side of it and give it a swift spinning motion.

Replacing the bearings and axle seals, while everything is already out, is cheap insurance for later down the road.

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