To lube or not to lube

So the only remaining question is - do I use permanently sealed u-joints or re lubable u-joints (assuming there is a choice in the size/series you are using)

This is not so simple to answer, and has long been the topic of many fierce debates. It may well come down to personal preference, but there are some points to consider.

Most importantly - relubable u-joints MUST BE re lubed. It sounds obvious, but the one thing you do not want to do, is to kid yourself that you will do regular routine maintenance on your driveshaft and u-joints, and the not. And yet, this is exactly what a HUGE number of people do. Avoid it. Be honest with yourself. If you aren;t going to re lube them - use the "permanently" sealed kind, if not, you will experience premature failure.

So, we have to be brutally honest with ourselves, fine. But what if we are the kind that actually would re lube the joints EACH and EVERY time they require it, properly, completely (see Part 3), and without fail (am I making a point here? There aren;t many people who fit into this category). Is there then any reason to prefer on kind over the other? You have to decide for yourself, but some advantages and disadvantages to consider are:

Re-lubable

* (-) They have to be religiously re-lubed, a PITA
* (-) They generally are not as strong, due to the grease channels in the cross
* (-) If you lose or break a grease zerk (not uncommon) the joint is useless (you could just replace it, but it it's been out for a while, way more contaminant will have ingressed into the joint than can even be flushed out by proper lubrication
* (-) Slightly more of a pin to install, as you have to get the grease zerks in the right place and all lined up
* (+) They are generally cheaper
* (+) Depending on environment, they may last longer (if conditions are wet and muddy, the ability to purge the joint and relubricate it, may well extend the life of the joint beyond that of a joint that cannot be relubricated. However, in dry condition, this will likely be much less of a factor.

Sealed

* (-) Depending on environment, may have a reduced service life than a relubable, since nothing is ever really 100% sealed, so that if contaminants do get in, there is no way to flush them out
* (-) More expensive
* (-) A bit more of a PITA to install, as you have to make sure you have sufficient lubricant in the caps before you install the joint, since you cannot add any afterwards.
* (+) Stronger, due to absence of through-cross grease channels
* (+) Less to worry about - don't require any maintenance.

Stupid question, but how easy is it to replace these things?

I would not want the strongest joints available. It just means something more expensive will break.

Have you experienced something else breaking with strong U Joints?

With all of the Engineering tools available Drive Shafts should only have their components like U Joints fail when they have been abused, used a lot, or neglected.
If some Dumb stupid puts a 1,000 HP engine into a Liberty and goes through the roughest off road coarse and breaks a drive line component, the debate should be weather he/she is having extreme fun or a candidate for the Darwin Awards.
I want reliability for my rig.

Takes some skill, you don't want to drop the needle bearings or have one slip into the cup.
The best way to tell if a U Joint is bad is to take the clamps off the yoke that attaches it to the axle or transfer case and move it by hand with out letting the cups fall off into the dirt. If it is not smooth, it is junk.
A second best way is to jack up the rear wheels, block the front wheels, put the transfer case in neutral and turn the drive shaft, slop or crunching is not acceptable.
I am leaning toward Precision Super Strong Regreasable from NAPA, the zerk is not in the cross to weaken it.
O'Reiley only sells the super strong in non regreasable.

Have you experienced something else breaking with strong U Joints?

With all of the Engineering tools available Drive Shafts should only have their components like U Joints fail when they have been abused, used a lot, or neglected.
If some Dumb stupid puts a 1,000 HP engine into a Liberty and goes through the roughest off road coarse and breaks a drive line component, the debate should be weather he/she is having extreme fun or a candidate for the Darwin Awards.
I want reliability for my rig.