Double Cardan Joint

I removed my front d-shaft on my 91 xj trying to isolate my driveline vibrations. To my surprise it was the front shaft that was vibrating. The double cardan joint is jerky. The u-joints seem fine but the little assy in the center of the joint is stiff. How do you grease it? Do i have remove the 1st u-joint?
Thanks, Brad tel

If its jerky...its too late. time to get it rebuilt. find a driveshaft shop in your area.

If there are any, the zerks will require a needle fitting for a grease gun to lube it.

Look at the thread I started a couple of days ago titled "Centering Ball Replacement: Front Driveshaft". It notes what I had to do to get one of these, with part numbers.

If it's the stock unit, there is no grease fitting. If it's an aftermarket, it may have 1 or 2 needle fittings in it.

You can get a kit to replace the ball assembly, which will require special tools, for ~$30, or you can get the whole thing (with a grease fitting!) for ~$65.

Interesting though, you say it's stiff? Even when clean? Mine had just a touch of noticable play in the ball socket. The new one has no play, it's stiff sort of like a new ball joint for the front end is (should be, it's made the same way).

Update: I disassembled the whole shebang and fond that there was some old grease in the u joints and they have no play but now that I have it apart I might as well just replace the u-joints and centering ball assy. Anyone know off hand what the part #'s are for some nice new Spicer u-joints that willl last another 220K miles? It's a stock 91 drive shaft driven by a 242 case.
I had a YJ several years ago that ate $20 u-joints for lunch. Then I got some Spicers from a tranny shop for $8 ea and never replaced another one. Cool huh.
Thanks