If your ball and thrust plate are not showing any wear, I would leave well enough alone. If your ball or thrust plate are showing wear, I would change BOTH the ball and the thrust plate. It is a relatively easy DIY job.
On a VPI, you'll need a pencil torch to carefully heat the ball near the ball/shaft-assembly interface (best to remove the shaft-assembly from the TT). After about a minute, once the glue holding the ball in the shaft-assembly breaks down, the ball will simply fall out. You may need to tap the
shaft-assembly
for it to fall out. Replace with a
ceramic ball type or your choice (grade 3 or 5, though grade 5 is very hard to find given its tighter specs). They are not too expensive.
If your thrust plate can be screwed out, great. If not (like the one in the Classic platter on my VPI Prime), you can just put the new sapphire thrust plate
(actually called a sapphire watch crystal or sapphire window)
on top of the old thrust plate. Will have the adjust the arm height accordingly, of course. The sapphire crystal/window should be a few mm less than the diameter of the old thrust plate for ease of servicing if needed.
The sapphire crystal/window are not too expensive unless you get one spec-ed to a higher lambda "flatness". Also, some may just use synthetic grease to get the sapphire window to "stick" to the old thrust plate for easier maintenance. I tried that on my VPI Prime, but using a very very small dab of super glue to bond the new thrust plate to the old one provided better W&F measurements on AnalogMagik and Fieckert Adjust+. Even with super glue, you should be able to remove the sapphire thrust plate if needed in the future. Main thing is to not get the super glue on anything when you install the thrust plate deep in the platter.
Whether you will get lower rumble will depend on how worn your old ball/thrust plate was, though it is measurable. At the very least, the platter will take a lot longer to spin down than before (presumably due to lower friction). I have noticed that the Phoenix Engineering Eagle/RR and SOTA Condor/RR need less voltage to maintain the VPI Prime at 33/45/78 RPM.
Whether it sounds better will depend on your ceramic bearing type and your ears.
