How do I change the left rear seal and bearing on a 2004 Honda atv

SOURCE: rear seal and bearing leaking on passenger side.

Basic to get tire and hub off, remove rear diff cover remove bolt, remove clip, pull axle out, then heavy puller to pull bearing and seal. Ck axle for wear

SOURCE: 2004 Aveo roaring noise from front and rear wheels that

wheel bearing or cv joint . remove brake caleber remove spindel nut outer bearing comes out easy inter bearing is is a little harder

SOURCE: I purchased my 2003 Jeep Grand Cherokee new, at

I wouldn't call that "normal" but, not completely unusual either. Many units will run for 300k miles without ever needing service past routine lube changes. Others will have chronic problems. It follows no real pattern.
Many times it can be traced back to the first failure which caused some slight damage from loss of lubrication and generated a bit of metal debris which throughout the entire time was never thoroughly cleaned out, instead, causing subsequent problems with other seals and components. Sometimes it is just "bad luck" that more than one less than perfect part found it's way into one item such as your differential. At the point you are at now, all this is just supposition as any evidence of the original cause has long ago disappeared.

SOURCE: Need detailed manual or assistance in replacing

You'll need to remove the rear end cover, remove the pin in the center pumpkin, push axle toward the center of vehicle and remove the axle clip, pull out axle. You may need a bearing puller to remove bearing.

SOURCE: 96 chevy blazer rear axle bearing/seal r/r

No. Did you run some emery cloth along the race (bearing surface) to make sure it was smooth and clean? If you leave any part of the old seal or debris on the hub surface, damage the seal when installing it, not liberally packing the bearing with grease or the seal did not seat right you can have issues like yours. Make sure the seal is installed flush and if everything looked good as far as the axle and surfaces, pack more grease in the bearing. When you think there is enough grease in it, put more in. Put the grease in the palm of your hand and with the bearing held flat in the other hand repeatedly tap the bearing on your palm until grease comes out both sides. Then put more on it when you seat it.