Just a word of advice, learned the hard way by more than a few hapless mechanics - when you replace that u-joint (and yes, it's available separately), be sure to lock the steering wheel in the centered position, ie take the key out of ignition, and ensure the wheels stay lined up straight when the joint is replaced. If you fail to do this, or if you happen to spin the steering wheel with the linkage disconnected, you will almost certainly destroy the airbag clockspring behind the steering wheel. This spring only turns a certain amount in each direction and if overextended will break, rendering the SRS system inoperable. Otherwise, a pretty straightforward job, but I've found it helps to remove the bolts on both u-joints to allow enough movement and slack to get the job done easily and without the use of Neanderthal-grade prybars.

I also have an 89 740. I'm currently having some issues with my steering. Would you mind taking a look at my post 'steering inconsistencies' from two days ago and let me know if these symptoms are similar to what you were seeing which led you to believe that the steering U-joint needed to be replaced. Thanks

The dealer told me I may soon need a new steering column lower u-joint ($128 part only) during an inspection (1990 740 wagon). I lubricated it and so far have no signs of it binding up, but if it does I will replace it. The mechanic told me "just bang it off".
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Keith in Maine 1990 740GL Wagon 245k AW70L B230F Red Block 8 Valve Non-Turbo Rex/Regina Non-EGR R-12 A/C

Why? This hardly ever fails. Have you tried lubricating it?