I'm asking this for a friend who has a 2001 Raptor.
While changing tires from dirt to sand we noticed that the left rear hub was loose so we pulled the cotter pin and tightened the castle nut. We also checked the right rear and it was fine.
After several trips to Glamis it's time to put the knobbies back on and the left rear hub is loose again.

Anyone else have this problem and what was the fix?
Thanks for the help.

 

look at the spline where the hub connect to the axle. See if they are stripped or something is not right.
If not you need to torque it good and with lockthread to keep from backing out.

To me sound like the spline is stripped.

 

Nope.
The spline looks fine on the axle and the machining inside the hub looks OK as well.

 

I had the same problem with a lone star axle. my hubs got "egged" out by the axle spline and kept loosening until I got new hubbs and used a breaker bar and cranked the chit out of it!!!

 

I don't know whether there is a fool proof solution other than frequent inspection. Proper torqueing to spec (85 fp, I believe) may be helpful. I have had the same occurence with both my Warrior and now the Raptor I guess it is the large degree of torque applied to the axles on these and other performance or sport quads, assuming no defective splines are present.
Your friend would be well advised to invest in a good quality torque wrench for this and other situations to avoid replacing the axle or worse.

 

i too had the same problem with my lonestar axel,i had my 350 pound brother in law break a snap-on 1/2inch breaker bar and they still came loose.finally i got pissed and cleaned the hub and slpines wih brake clean then took my 1/2 inch ingersol rand impact too them,havent come loose since.

 

I also had the problem with my LoneStar axle. The splines on the LoneStar axle aren't as thick as the ones on the stock axle, so the hubs jiggle forward and backward under load and loosen up the castle nuts that are, of course, pressed tightly against them. When I complained about this to LoneStar, they told me I could send back the axle to them (at my expense for both send and return shipping = $50 or more) and they would build up the chrome on the splines for me for an additional fee. Or I could buy their hubs which supposedly would get rid of the problem. I was more than a little peeved that they didn't check for proper fit with the stock hubs before they shipped the axle out to be sold. Apparently I'm not the only one who has had this problem with a LoneStar axle. There is no way in the world that 80 or 90 ft lbs is going to hold those castle nuts on for more than a few rides. Believe me, I've tried it.

 

Its not just the Lonstar I have the same problems with my Dura Blue. I went to 140 ft/lbs and they still loosend up. Now I just tighten them when I start to ride.

 

This hub thing must be a raptor thing. I am constantly checking my rear hubs for loosening. I have the left rear(chain side) come loose every other ride until I went to Autozone and bought 14 mm shaft, 7/8 head lugnuts and washers to replace the stock cotter style nut. I used a butt load of blue locktite and torqued those puppies down hard. Seams to be working for at least the last four rides. Just wish the rear axle bearing held up after the last ride. Bummin

 

I have Durablue axle and not very often it start to come loose. I just slam the impact wrench and beat the heck out of it. I alway made sure it tight before racing or just playing ride.
just a habit I have to make sure nut and bolts are tight.