My E825 has 4500+ on the odometer and makes some noises. I though I had a bad bearing in the diff. When I took it out I think my issues is the splines being worn out. The symptoms are the grinding noise whenever not fully on or off the pedal. I replaced the rubber with the one from Polaris, not a long duration fix. Question is which side is softer the motor side or diff side? I’m thinking about a motor upgrade but think I will need to fix the diff at the same time.
Do the newer diffs fix in the older E825? If so, I have a donor I can use.
That input shaft is really easy to replace and relatively inexpensive, you just pull the c-clip and the shaft will pull right out. The large bearing isn’t made anymore though, so you have to change things a bit. The bearing issue you are experiencing could be one of the bearings on that shaft.
Get in touch with Rodney @Old_Houseboater. He usually has replacement differential input shaft kits with upgraded oil seals.
Remember to use a new bumper.
I swapped out shaft with one purchased from Rodney. It was easy to put in. It got rid of a lot of the noice but I still have some other warn parts in there that are worki g good enough for now. If I turn the radio up I can’t hear it 
I put spline grease on mine and it seems to help . will defininently help with wearing .