Greasable or non-greasable, that is the question...

if there is any movement at all.
replace.
i had a tiny amount in one and replaced it today.
better safe than sorry.

 

greasable all the way. Anything that moves should be greased. Guess I get that from machinery.

 

Permanently sealed systems, like a non-greasable u-joint will not lose any grease and will not take on water or contaminants. Install them, leave them alone, use them and forget about it.

 

Correct, if you blow a seal it doesn't matter if it has a grease fitting, it will take on moisture and fail anyway. The chances of ruining a seal are way greater if you force grease into the joint.

 

Years ago when Warn was testing axle shaft strength they also tested a bunch of different U-joints to know what to recommend for use with their chrome moly shafts. The Spicer non-greaseables tested the strongest of all the stock style, parts house U-joints. The Spicer greaseables were either 2nd or 3rd on the list. That of course does not include the superstrength joints like CTM's, OX, etc.
I don't remember the actual numbers but I do remember which was #1 fwiw.
I use greaseables in my drive shafts and non's in my front axle because the front axle needs the strength and the drive shafts turn way too fast and generate too much heat to use non greaseables imho.