I like to swap out some parts based on the amount of time they have been there, and or miles, even if they don't show sign of wear. U-joints are a good example for me, especially since most are no longer are serviceable. No grease zerts. Does anybody remember or could check the next time you are under your Jeep to see if the stock joints on the rear drive shaft have zerts. Mine does not.Looking on-line, some replacement joints have zerts,others not. I like to use joints with zerts so I can grease them at every oil change. So i can't tell from just looking at these if they are stock. The snap rings are a little tweaked, not entirely in the groves. That happens sometimes when the joints are replaced and not done correctly. This suggests they may have already been replaced at some point. Our Jeep has 140,000 miles on it. I think they are due, but not if they have already been done. I have only owned the car a year so don't know if they have been.

 

Okay. here's the thing. Original u-joints don't have fittings and replacement may or may not, depending on what you buy. The major problem with having fittings is, most of the time, there isn't room for the standard grease gun coupling to snap on to it. They DO make slim couplings, but they don't last. They tend to blow apart or pop off easily. What I've always done with mine on all my vehicles is pump them full when I changed them BEFORE putting the driveshaft back into the car. You have to put a c-clamp on the rear one to hold the caps on when you do this, but it works. I've seen some u-joints with fittings on one cap, but they are hard to find and are mostly used on heavy trucks.

My method seems to make them last a lot longer than going with just the pre-packaged lube. You can also pack the caps with more grease before assembly, but that gets messy.

 

I have had that problem as well. But sometimes I can get a grease gun in there and on the fitting, sometimes not. I think it's vehicle specific. Right now, on my Chevy, I can get the gun on the rear zert but not the front. I have to dismantle the front yoke, drop it down. Hold the two cups together, fill it with grease and then reassemble. PITA.
I have used a needle fitting as well on the gun.

 

I'm an old Chevy truck guy, and you don't have to take the front joint apart, but you do have to pull the rear joint and swing the driveshaft to one side to access the front zerk.