Yeah, I didn't even see the post dates until after I sent my note. You are correct the rear end issues are terrible on the 420's. What I can't believe is from 2007 on and they are still making them the same way. Very disappointing!!!

 

The problem with the rear end wasn't the diff, it was the axle shaft, we sold dozens of 420s and every time I service one I check the hubs and that tube between the axle nuts and the diff, 9 times out of 10, one of them is loose. I've never had a diff problem except when the axle shaft has worn the crownwheel splines so bad we have had to fit a new crownwheel. Honda fitted a different rear axle to the new model that came out in 2013, but Honda dealers won't allow us to sell this model, so we haven't much experience of the new one. However the "new" axle looks a lot like the old 350 axle which did not give any trouble.

 

Help me understand how the loose axle nuts are allowing water & mud into the differential and taking the pinion bearings out?

 

Like I wrote above, I've never had problems with the 420 diff. The rear end is fairly similar to the old 300 and we have had diff problems with them, I assume because the left hand diff bearing doubles as the wheel bearing, once it gets a bit of play, water can get past the seal and starts to wreck the other bearings.

 

I'm beginning to think we are on different pages. We have lost (3) pinion bearings in the rear differentials of our 2011 & 12 Rancher 420's over the past couple of months. We have changed the rear diff oil after each ride but the mud & water getting past the pinion seal is destroying the pinion bearings. If anyone has any suggestions other than gun grease, I would greatly appreciate your suggestions.

 

Like all SRA they have no wheel bearings at the hub. The Bearing is in the diff #36 #37 are the wheel bearing and the seal #40 and #41 keeps the water out of the diff. The only other way for water to get in the diff is seal #39 through the drive shaft and the filler hole #3 #42.

 

Thank you so much for all your help and I will always make sure to check the tightness of the axle nuts. I can't help but think the water & mud is entering past seal #39 given we have lost (3) #48 pinion bearings. I turned the seal around on one of the machines and the oil is really clean, I am going to install a speed sleeve on the driveshaft end, turn the seal around and install a sealed bearing at #48. I will remove the seal from the inner side of this bearing to ensure it can lubricate. Please continue to share your knowledge & experience and I will do the same.

 

On the old 300 item 4 is enclosed in a tube that forms part of the swinging arm assy, this tube is sealed onto the back of the engine with a rubber boot, and we still get collapsed pinion bearings.

I've spent many an unhappy hour trying to poke item 13 out through the tiny hole in the casting, you then stand a chance of getting bearing 38 out with a slide hammer. Why do they fit that spring ring? The bearing can't go anywhere anyway.