One more vote - replace it. As the others say, once it starts squeaking it is already chewed up. I had a Lous Europa and the rear u-joints set the camber on the rear wheels. Since the joints were seriously side-loaded they didn't last long and I replaced them literally dozens of times. When I heard the squeaks I got another set of joints and replaced them... the noisy one was obvious by the flat spots on the needle bearings.

If it is squeaking, then I would say you have a failing seal and the grease is gone. Sooner or later the U-joint will fail, you may as well replace it before it causes any damage due to a future failure. And I have not heard that non-greasable joints are stronger, but they could be as they have no hole drolled on an inside corner to tap in a zerk fitting.

There is not . outside , to a u joint. all the moving parts are on the inside. if the bearings inside are dry and squeaking , The joint can still not feel loose. it wont feel loose until some of bearings begin to disintegrate.

Just plan on replacing it before that happens.

HUH?? I suggest you take it to the dealership. Never have I seen spraying WD-40 on a sealed U-Joint on the outside make it stop making noises. And no, you cannot grease a sealed u-joint, once they go bad. You replace them

you can repack the u joints or replace them with a serviceable type.

If it is making a noise then it has already started to fail and it is too late to save it. Just replace it because it will get worse rapidly.

I'd say replace. Their not that expensive and to me if you can grease it, it's always better.

My U joint started squeaking recently. I got some grease and went to grease it only to find out it is non-greasable.

The U joint seems fine. There is absolutely no play in the drive shaft. There's just that annoying squeak. The source seems to be on the outside because I sprayed WD-40 on it and it stopped until it rained today.

Should I or should I not replace it? I also heard non greasable u joints are stronger.