well i was riding the atv today and got in a hole that i shouldnt have been in but i locked it in 4wd and gave her hell it came out of the hole but then i backed into another hole to "test the waters" i wanted to be sure i could get out of it before i went "all-in" when i tried to go forward the back tires started to spin so i stopped put it in 4wd again and gassed on it. I WAS STUCK BIG TIME i got pulled out and then i noticed that i only had the front tires pulling UH-OH now i hear the rear diff making all kinds of racket so i cut it off. i finally went home and started jacking it up and found out that when i rotate one of the tires the other tire turns with it so i am thinking ok cool i at least i didnt break the diff so the rear diff seems fine but i can hear a bad clanking noise. the question i have is could i have stripped the splines on the shaft going into the rear diff or what could be going on and how do i fix it (pics and text preferred) i need a picture diagram to show me what to expect when i start what to check what to replace and instructions as this is going to be a first time tearing into anything like this but i am very able to do the work just need to know how to do this. also how do you remove the rear diff and the whole axle.

 

Usually the coupler on the rear prop shaft strips out. Mainly because a lot of people don't grease the zerk fitting or don't even know it's there. Has a hole cut out in the box frame to access the fitting. If the rear wheels turn in neutral,but the prop shaft doesn't or grinds,sounds like the problem. I had to replace quite a few on the 325,330 and 500 Magnums. Swing arm has to be removed or the rear diff to replace the coupler. Not a fun job for a $30 part. Item #17. Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse
Don't have 99 500 manual,but this 2003 330 Magnum manual has the same rear drive system and will help on repair. http://gh-ftp.com/ORV%20Manuals/Pola...3%20Magnum.pdf

 

old polaris tech you have helped me a lot and i am so glad that you do this because people like me cant seem to catch a break so you are like a beacon of light decending from the clouds of the big polaris heaven in the sky. btw i turned the yoke and if i turn it slow the axles turn but if i rotate it fast then the axles stop turning and that is when i hear a clanking/ grinding noise but when you turn the axle itself both of the axles turn as fast as you want to turn them by hand of course lol but the yoke will almost stop spinning and you can hear the grinding. oh and how do you feel about welding the yoke to the shaft on the diff somebody told me to do that and i was like uh no i will not but after thinking on it i was like i see how it could work but its not really my way of fixing something i prefer to fix it right but the welding wouldnt cost me anything and since i dont have a job now that seems to be the better option just wanted your opinion of maybe some of the pros and cons of it

 

old polaris tech you were right i pulled the whole axle out and the coupler and the teeth are wore out on that coupler and the pinion so my question is where can i buy a new pinion i dont want to have to rebuild the whole axle with a new ring and pinion but i have to replace the pinion and the coupler for sure. do you have any idea where to get the pinion at.

 

Usually the pinion shaft doesn't wear down as the coupler is made from softer metal and it takes the brunt of the punishment,but if the pinion splines are stripped also,not much choice other than a new one or finding a rear end that's parted out on ebay,etc. Spot welding would be the last thing I'd do as it just complicates things if you ever have to do any work later on. About $180 new plus the price of a coupler.Dirt Cheap Yamaha, Honda, Arctic Cat & Polaris OEM Parts & Accessories – Cycle Parts Warehouse

 

well i can reverse the coupler around and there is no play in the coupler but if i look at the pinion shaft itself the splines are kinda like a skillsaw blade shape they arent real bad but it is still that the fact that they are like a skillsaw blade shape that has me worrying about putting a new coupler on it to have it just strip the new coupler because of the pinion shaft. idk not too sure what i need to do but i am glad that you have helped me as much as you have.

 

To be honest with you I've installed new couplers on ones that had to be pushed in, would just grind,couplers were completely destroyed and they still had fairly decent enough splines on the pinion shaft and prop shaft to work.That's why they make the couplers out of softer metal so it can take the brunt of the force.Worth a shot at 30 bucks for the coupler even though it ain't the best job in the world to work on a rear diff and swing arm on a Magnum.If it solves your problem just keep it greased!

 

Hi OPT,
Which side/location is the cut out for the grease fitting on. Want to make sure I have not missed it. I ended up getting the specific model service manual as well as the 1999 manual and all it says it locate grease fitting and grease.

 

Just follow the prop shaft as it goes through the rear swing arm. Last cut out hole on the right as you are facing the rear of the machine. You have to roll the atv until the zerk fitting is straight enough to get a grease gun on it. Flexible grease hose works best on all the grease fittings.

 

old polaris tech what about if i put a new coupler on it will i still be able to do the hard riding that i usually do or is it going to be something that i am now going to have to take it easy on it and never play with the bike anymore. if i have to take it easy on it from now on then i might as well just buy the new pinion gear and be done with it and know that i can go play in the mud and climb hills again.