Hear a grinding noise around the differential area when accelerating while going straight or right. Noise is less when not accelerating and at speeds at or greater than 50MPH. Almost no noise at the higher speed even when turning right. No noise during the following conditions, when turning left, in neutral, clutch pushed in, when front end of car jacked up and shifting through all gears and turning right/left at different speeds.. Car is Geo metro 3 cylinder, 5 speed, 221,000 miles. No noise or problems when shifting gears (runs like new). Noise began after replacing drive axles and transmission fluid (used Synchromesh manual transmission fluid recommended in service manual), Replaced drive axles, right wheel bearing, tie rod ends, clutch, flywheel, pilot bearing, throwback release bearing, right and left drive axle seals. My car has 221000 miles. My car has a 5 speed manual transmission.
After reviewing your case I have concluded the left wheel bearing should have been replaced as well. In most cases when you can make the noise change by turning or swerving then a hub bearing is worn. I see you have replaced the right wheel bearing already. I would look to the left wheel bearing to be in need of replacement.
I checked the left wheel bearing by raising car, spinning wheel manually as well as accelerating 1-4 gears. I do not hear any grinding noise in the left wheel or right bearings under these conditions. I also tried wiggling the left wheel (hands at 12 & 6) while raised, but virtually no play in the wheel. As stated above, it makes grinding noise when accelerating going straight, but noise it greater during accelerating if I turn right even slightly (4-5 inch turn). Also, if the left wheel bearing was bad I would think it would make noise when turning left versus when turning right.
It is about the side pressure on the bearing along with the weight of the car. This is why it is difficult to diagnose on jack stands.