Yamaha ATV/4 Wheeler Problem

I noticed that one rear wheel was wobbling on the axle of my 2005 Yamaha Big Bear 400 4 wheeler. I thought it would be a bad wheel bearing but after pulling the wheel and wheel hub, I discovered that is a splined assembly. There is no wheel bearings at the wheel hub.

The problem I have is apparently the axle shaft nut there did not have a cotter pin in it from the factory, the nut backed off a bit which allowed the wheel hub assembly to become loose on the splined axle shaft. No telling how long this has been loose but it has worn the splines in either one or both the wheel hub and/or the end of the axle shaft.

I cleaned it all up, brushed all of the rust and corrosion out of the splines, applied marine grade grease, reassembled all, tightened up well with new heavy duty cotter pin. After a test ride in the woods, I found the wheel hub has loosened up again and is wobbling on the axle splines. I think the splines in one or both are worn to the point they cannot prevent the hub from being a sloppy fit on the shaft and it will wobble around and continue to wear.

I am guessing I will have to replace one or both wheel hub and/or axle shaft. If the rear axle has to be replaced, that will be a major deal as the rear end will likely have to be disassembed.

Any experienced Yamaha ATV mechanics out there? I need some info.

Thanks, Dave

U can replace the axel with out rear end being tottally disassembled. But for a cheaper fix u can just weld the hub to the axel for now until u need to replace the brakes or bearings. Then replace the axle and hub or hubs.

you can also order new hubs or get them off ebay, i have had a lot of success with this. the axle is much harder than the hub, so the hub wears before the axle most times.

Suggestion- Wrap the axle spline with the smallest lead solder you can get, not too heavy of a wrap, than reinstall it all. This should compress into the void's and correct itself till all new parts can be assembled.
This is an old machinist trick to shim dies up till time to resharpen them.

I can clearly see the splines on my axle are worn down alot. The splines inside the hub are probably as badly worn, if not worse.

I found some very thin brass shim material and cut a strip exactly as wide as the splined section of the axle, wrapped the brass shim material around the axle, and cut it exactly the length of one full wrap.

Slowly worked the hub onto the axle splines over top of the shim material. It took a while, but I finally got the hub all the way onto the axle splines. Replaced castle nut, tightened as tight as I dare, replaced cotter pin. The wheel hub then felt pretty tight on the axle.

I have run the 4 wheeler several times since and am just now noticing that the hub is getting loose on the axle splines again. Not sure if I can repeat with a new and possibly thicker shim material or not.

The brass shim material I am using is just a few thousants of an inch thick. I doubt I can get the hub over anything thicker than that. The solder sounds like it would be much too thick and it would not be possible to get the hub on the axle.???

Anyone have an electronic copy of the repair manual for this ATV or can tell me the steps to remove and replace the axle?

Thanks, Dave

give this link a try, http://www.maxmekker.com/atv.asp


downloadable service manuals

I went to the maxmekker website, downloaded one of the manuals and it is a supplemental manual of some kind and not the real repair manual. I have found that same thing on several repair manual web sites. I don't know what the deal is on those manuals but they do not provide much mechanical information.

My 4 wheeler is a 2004 Yamaha Big Bear 400 4 wheel drive. Its model number is: YFM400FWS. I have tried, but am unable, to find an on line service/repair manual. Not sure if I am looking in the wrong places or not.

Dave

http://www.partforyamaha.com/pages/parts/viewbybrand/2/Yamaha.aspx


try this, go to rear wheel, schematic for axle removal

get a bar and tighten as tight as you can ,run it for awhile then retighten. do this a couple of times and it should help.

That was a good breakdown for parts, part numbers, prices, etc. I noticed the axle price there ($237) was much cheaper than what I had been quoted here locally ($378). Shipping would add to the cost though.

Not sure of the steps to actually remove old and install new axle. Shouldn't be too tough, but would like to know how it comes out, goes in, etc. A service/repair manual may list the axle replacement, steps, what order, etc.

I have tightened the nut as tight as I thought I could without stripping the threads.

Dave

You might want to try and swap the tires from side to side. If the one from the other side stays tight, then just buy a new hub and put it on. If it gets loose too, you'll need to replace the axle and hub assemblies.