Dear wise-folk, turntable motor grinding after oiling?

This is a 40 year old turntable, a high quality belt drive Pioneer PL-41. After dropping a couple drops of 3in1 oil into the motor lubrication point (the manual says to lube it regularly), the motor developed a quiet grinding sound.  It took five hours of play over a month before I noticed it with my ear next to the platter.

Did I stir up some gunk in the motor?  Thanks in advance for any suggestions!  You are so helpful!

PS This sounds like a pinch of sand is in the motor, but the grinding/crunching sound is quiet.
Did you also lubricate the shaft? If not give that a try!
Sadly it sounds like the bearing is going bad these things do wear out especially if it runs dry. Or improper maintenance over the years has left it in this condition. By oiling it you have no doubt loosened things up. If you grab the motor spindle can you move it up/down/ back/fore?? If you CAN that would surely indicate a bad bearing.

Matt M
I would take it apart again and clean both the male and female parts of the bearing, as best you can using lens paper and maybe some pure alcohol. (I prefer photo lens paper, because it does not fragment and leave scraps buried in the bearing well.)  Then use a thicker oil; if memory serves, 3 in 1 is very thin machine oil and may not be sufficient viscosity for your aged bearing.  I use RedBall 0W20 synthetic motor oil in 3 of my vintage turntables, and I am very pleased with the results.  Of course, a dozen other people will give you a dozen other recommendations for what oil to use.  

While you've got the bearing apart, look for wear on the thrust pad and on the ball itself.  But scraping sound suggests that the spindle may be wobbling in the shaft, up higher above the bearing per se.  As someone else suggested this is detectable by wiggling the spindle.