Put the bike up on stands so all wheels are off the ground. loosen the boot between teh engine and the rear swing arm. Turn the rear wheels by hand, if the shaft isnt turning its an issue at the rear diff.

Next, take off the oil fill cap on the rear diff, start the bike and place in first gear which would normally turn the wheels. With no strain they may turn, but if you apply the rear brakes It will stop, but look in through the oil fill cap to see if teh large ring gear is turning.

If it is, this means that teh rear drive shaft is probably OK, and the problem is in the coupler where the drive shaft slides through the differential.

 

To avoid this happening - keep the seals good, avoid too strong power washers, a hose is better, and every couple years actually drain the diffs and replace the gear oil.

 

First-thanks to Zitaron - excellent tip about power washing the seals out - I hadn't real give it much thought -but I now surely can see that 2500 psi could and would reak havoc on oil seals. Beauty (and clean) are only skin deep but grit and grind goes to the core (splines and all).

GREASYGAS : I have the same exact problem with my (actually my father's - 450ES 1999) I came upon this forum while looking for ring gear. Had already bought axle/ seals etc and thought the inside splines were ok in r gear. Viewing the 'axle-hole' in the gear (still in case) the spline appeared usable. But later when rg removed and cleaned for re-assembly -I re-examined closer and those splines also were extremely worn where contact was made with axle splines (what appeared the first time was the very edge(or end) of the splines which for about a 1/16 th inch lengthways were ok -but not the rest - almost worn flat Actually i can hardly believe the rear wheels were pulling long before they stopped. Like others have said - no noise, except one last little pop I did not realize the rear driving was gone at first. I suspect you have same. It was caused by lack of flushing and changing gear oil and determining seals were infact -intact. We made mistake of depending on the seal job by Honda to keep the grit out and just did not realize this particular 4 wheeler had ever had the axles submerged. ( Dad is 71 - hmm, i susupect my little brother...) The drive shaft/ pinion end was perfectly clean and lubed - (its in a better position to resist infiltration of outside abrasives) My bearings seem ok although I'm replacing. Bearings just have weight and rotation forces as opposed to the engine driving force on the ring gear and axle's splines - Anyway i will continue on another post ...

 

Greasygas.. I don't want to ramble on - "action450s" sounds very knowledgable and excellent advice - i would like to add that the wheels turning / ring gear not - thing may not be as cut and dry - i had the confusing issue of having the worn-out ring gear splines and axle splines re-engaging after I got the wheels off ( I had a stubborn wheel nut and put opposite wheel nut back on axle or something) - don't exactly remember, but what happened the axle simple shifted slightly to the "passenger-side" and allowed those bits of unworn splines (referred to in last post) to re-engage with r gear and really confused me during my 'diagnostic phase'. I am much the amatuer if you haven't already noticed. Anyway, the contact point where engine revolution turns to wheel rotation {ie ring gear splines to axle splines} was bathed in greasy sand so it didn't hold out. I bought shop manual etc. and it warns about cost of special tools needed etc. and particularly if shaft and pinion need removing, but I bet you same problem - and just as I - its nothing time and a certain sum of money can't fix. By the way - i did not have to "heat the gear case in an oven to exactly 140 degrees for 30 minutes to remove the ring gear.." That's some of the stuff in the "factory - how to / shop manual"
If you decide to "go-in the rear-end" and rebuild I will glady share what little bit of info i can - just reply back on this thread and I will check in in a day or so - Good Luck

 

Hi guys Im new to the system but i seem to have the same problem as tommycat. I recently was pulling my small boat with my wheeler when i got hung up in the mud, once that happend i gave a little more gas and she popped. Anyone know what that noise could have been and also does anyone have any videos on how to replace the axle myself. Thanks and HAve a Great DAy.