Still working on my tranny swap and I've been examining components before I put them back in.

The throw out bearing on my OLD transmission spins freely for about 6-8 seconds, and the throw out bearing on the new (slightly used) transmission stops spinning as soon as I take my hand off it.

My question is, which behavior is normal...?

I might have gotten brake cleaner on the newer throw out bearing once upon a time when I was cleaning it out... which might be why its acting like this now. :S But I can't remember for sure.

put some pressure on it and spin it with your hand, if it feels rough when you move it toss it and get a new one.

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Its installed on both transmissions still (attached to the fork)... will this "test" still work, or will I have to pull it off and do it?

It's not that hard to pull it off the transmission and put it back on, it only clips onto the fork

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beauty - thanks. didn't want to attempt it and make more work for myself.

a new TO bearing is greased up and should stop spinning immeadiatly, a used one that grease has broken down and worn out so it spins more freely. that means the bearings inside it dont have as much protection and lubrication. you really should replace the TO bearing anytime you change the clutch. for 20-30 bucks its a safe thinig to do

Exactly as Smaay said.

New = Tight seal and lots of grease = resistance = stops spinning fast
Old = Worn seal and little to no grease = less resistance = spins longer
BAD = deal seal and no grease = Damaged bearing = no spinning