Somebody in another thread (wish I could remember which one) gave me the idea to poke a hole in the rubber boot behind the center bearing and pump the boot area full of grease with the grease gun. I just tried this a few days ago and it seemed to work well. I don't know how long this will last, but it was way too easy to do and it definitely helped!

Here's what I did:
- Used a pointy O-ring pick (sold in a set of 4 with different angles, look like dentist's picks somewhat) to stab a hole into the rubber boot (located on the rear side of the center bearing). I poked the hole in the flat section of the boot right next to the molding seam in the boot so I could find it again next time. Hint: clean this up so you don't pump dirt inside the boot.
- grabbed the old grease gun and fitted it with the nice, pointy hi-pressure grease tip.
- poked the HP tip into the hole in the boot and pumped away until grease came out around the front and rear of the boot.

As a side note, if/when I ever replace the center bearing, I'm going to pump in grease on the new one too. The boot doesn't fit tightly and I can see water working its way in.