If you've been hearing a nasty clicking sound while turning or noticed a grease-covered mess under your quad, your 1999 polaris sportsman 500 rear axle is likely waving a white flag. These old Sportsmans are absolute tanks—there's a reason so many of them are still tearing up trails decades later—but the CV joints and axles aren't invincible. Eventually, years of mud, water, and heavy loads take their toll, and you're left with a decision: fix it now or wait for it to snap when you're five miles from the truck.
Honestly, the 1999 Sportsman 500 was a bit of a game-changer back in the day with its independent rear suspension (IRS). While it makes for a smooth ride, it also means you've got two CV axles in the back instead of one solid shaft. When those rubber boots tear, it's only a matter of time before dirt gets in and grinds those bearings into metal shavings. If you're at that point, don't sweat it too much. Swapping out an axle isn't exactly a fun afternoon, but it's totally doable in a home garage with some basic tools and a bit of patience.
Knowing When Your Axle Is Shot
Before you go out and drop money on a new 1999 polaris sportsman 500 rear axle, you want to be sure that's actually the problem. The most common "tell" is a rhythmic clicking or popping sound when you're moving, especially if it gets louder when you're turning or the suspension is compressed.
Take a look under the back of the machine. Are the rubber boots intact? If you see a tear or if the boot is missing entirely, that's your smoking gun. Once the grease leaks out and the trail grit leaks in, the CV joint is toast. You might also feel a weird vibration through the seat or floorboards when you're hitting higher speeds. If you can grab the axle bar and wiggle it significantly back and forth (or up and down) at the joints, the internal tolerances are gone. It's time to replace the whole unit.
The Struggle of Removing an Old Axle
I'll be real with you: getting the old 1999 polaris sportsman 500 rear axle out of the rear differential is usually the hardest part of the job. Because these machines are over twenty years old, rust and "character" tend to fuse things together.
You'll start by getting the wheel off and removing the hub nut. Usually, that's a 1-1/16" or a 27mm, depending on what's in your toolbox. Once the hub is out of the way, you've got to disconnect the upper or lower control arm to give the axle room to swing out.
Now comes the "fun" part. The inner CV joint is held into the differential by a small metal circlip. In a perfect world, a sharp tug on the axle would pop it right out. In the real world—the one where we ride through swamps—that clip might be stuck. Sometimes you have to get creative with a pry bar or a brass drift and a hammer to persuade it to let go. Just be careful not to damage the differential housing. You want to apply steady, even pressure or a quick, sharp "pop."
Picking the Right Replacement
When you start looking for a 1999 polaris sportsman 500 rear axle, you're going to see a massive price range. You can go the OEM route, which is usually high quality but will make your wallet cry. Then there are the "budget" axles you find on the big online marketplaces for fifty bucks.
My advice? Find a middle ground. There are plenty of heavy-duty aftermarket brands that offer reinforced boots and better-than-stock internals without the dealership markup. Since the 1999 model isn't exactly a high-horsepower racing machine, you don't necessarily need "pro-level" racing axles, but you do want something that can handle a thick mud hole. Also, double-check your fitment. Polaris changed things up occasionally, so make sure the spline count on the inner and outer ends matches your specific year and model.
Putting Everything Back Together
Once you've got your new 1999 polaris sportsman 500 rear axle in hand, the installation is mostly the reverse of the teardown, but with a few extra steps to make your life easier next time. First, clean out the splines inside the differential and the hub. If there's old grit or rust in there, the new axle won't seat right.
Apply a healthy amount of anti-seize or waterproof grease to the splines. This is a huge favor to "Future You" for when you eventually have to do this again in five or ten years. When you're sliding the new axle into the diff, you'll feel it hit that circlip. Give it a firm push (or a light tap with a rubber mallet on the outer end) until you hear or feel that "click." Give it a little tug to make sure it's locked in place. If it slides right back out, it's not seated, and it will fall out on the trail.
Don't Forget the Maintenance
It's easy to just slap the wheel back on and call it a day, but while you're under there, take a look at your wheel bearings and bushings. If the 1999 polaris sportsman 500 rear axle was bad, there's a good chance the bearings have been taking some extra abuse too. If there's play in the hub after you've tightened everything down, you might be looking at a bearing job next.
Also, keep an eye on those CV boots every time you wash your quad. A tiny hole can be patched or the boot can be replaced for ten dollars if you catch it early. If you ignore a torn boot, you're looking at another hundred-dollar axle replacement. It's all about staying ahead of the wear and tear.
Why This Specific Model Matters
The 1999 Sportsman 500 is a bit of a legend. It was the "Big Dog" of the utility ATV world for a long time. Because it was so popular, parts for the 1999 polaris sportsman 500 rear axle are everywhere. You aren't hunting for some obscure component that hasn't been made since the Reagan administration.
The simplicity of this machine is its best feature. There's no complex electronics or sensors on the drivetrain to worry about. It's just mechanical parts doing mechanical things. As long as you keep the fluids fresh and the axles greased, these things will honestly outlive most of us.
Final Thoughts on the Job
Replacing a 1999 polaris sportsman 500 rear axle might seem intimidating if you've never pulled a suspension apart, but it's one of those "rite of passage" repairs for ATV owners. It saves you a ton of money over taking it to a shop where they'll charge you eighty bucks an hour just to look at it.
Once you get that new axle in, the difference is night and day. No more clicking, no more vibration, and no more worrying if you're going to snap a shaft when you're climbing a rocky hill. Just get it done, get the grease off your hands, and get back out there. These old Polaris machines were built to be used, not to sit in the garage waiting for parts. Keep it maintained, and that Sportsman will keep hauling wood, deer, or just yourself through the woods for plenty of seasons to come.