Are sealed fittings on steering linkage less apt to fail?

When they first came out, that was how they were touted. By having nylon parts instead of rubber, and lithium grease instead of (what…lard?), they were supposed to enable long warranty times with no lube required.
But all repair shops ask if you want to swap them out for the old kind. Wouldn’t that just put you onto the old schedule of getting frequent lubes as the grease dried out?
What’s the SD?

To clarify the terminology a bit: steering linkage joints, such as tie rod ends, may or may not have grease fittings. The same is true of suspension joints such as ball joints.

Years ago, all these joints had grease fittings (little nipples to squirt grease into) to allow for periodic lubrication with fresh grease. As improvements were made in both the joints and grease, we starting seeing “lubed for life” joints without grease fittings. The idea was that the factory grease would hold up for a long time if the joint was sealed to prevent contamination.

Some of these lubed for life joints had plugs that could be removed in order to install grease fittings. Presumably, maximum life could be achieved by leaving them alone for a while (50,000 miles?), and then starting to grease them. Some lubed for life joints are totally sealed and have no provision for grease fittings. Neither design is perfect. The benefit of adding fresh grease is offset by the inevitability of some contaminants getting in through the grease fitting.

Nowadays, totally sealed joints are by far the most common. The overwhelming majority of Asian cars have had them for many years. I believe that’s true of European cars as well. Some American cars have a full set of greasable joints, some have a full set of totally sealed joints, and some have a mix of the two designs. It’s just one of the choices design engineers make.

So probably, if the joints have plugs and are up there in miles, you can prolong their life by installing grease fittings and lubing them. The concern isn’t the grease drying out so much as breaking down over time. Realistically, it would likely make some difference, but not a huge difference.

Thanks for the commentary, Gary T. My old truck had 395K miles when retired and excepting tie rod ends never needed any repairs, I believe owing in part to regular chassis lubrication. The replacement truck had plugs where I wanted fittings, so I’ve installed them, believing that a few minutes with a grease gun every few months is cheap insurance.