Let’s talk about your Polaris RZR’s transmission, or Pandora’s Box as I’m sure some of you call it. Your transmission is the big control box that takes the power from your engine and uses it to make your wheels turn the direction you want them to with the right amount of power. It’s very important to say the least.
One of the most important parts of your transmission is the pinion and front output shaft. The pinion shaft uses a spiral bevel gear (also called a snorkel gear in this application) to turn the front output shaft. This turns your prop shaft which delivers power to your front differential, thus making four-wheel drive possible. If you want four-wheel drive, then you want your spiral bevel gear to keep doing what it’s doing.
The problem is that the gear meshing between the pinion shaft and the front output shaft is one of the biggest weak spots in your transmission, and we often see transmission failures in this spot. But what causes those failures and why? Let’s take a close look at this costly break and see what exactly you can do to beef it up to save a few bucks.
First, let’s take a look at the spiral bevel gear itself. “Spiral bevel gear” sounds like a complex industry term on its face, but it’s quite simple when you break it down. “Spiral” means that the gear teeth are in a spiral pattern instead of being straight. “Bevel” means that it’s slanted instead of straight. The result is a gear in the shape of a cone with teeth spiraling around it like it’s trying to hypnotize you.
Polaris uses spiral bevel gears because they are very strong… when you’re driving froward. When your RZR is moving forward, the shape of the gears actually pulls them closer together and gives them better meshing for smoother, stronger gear mating and less heat buildup. The problems start when you throw the machine in reverse.
The spiral bevel gears on your RZR most often break when the machine is in reverse. That’s because they tend to want to pull apart when they run in reverse. There are a complex set of forces involved to make them pull apart that we won’t get into, but when they pull apart even a little bit, the meshing can be bad enough to do damage.
That’s because bad meshing puts extra leverage and stress on the gear teeth. You want the whole tooth of one gear to push on the whole gear of the other gear. If you have meshing where the tip of one tooth is pushing on the tip of another tooth, it’s going to break.
The transmission case and the pinion bearing retainer ring are designed to stop those gears from pulling apart, but your transmission case and your bearing retainer ring are probably a little hotter and softer than they should be if you’ve been riding all day. The case and the retainer can flex and allow the gears to come apart for a split second. Unfortunately, that’s all it takes for you to chip a tooth and lose both gears, your case, and the rest of your trip.
Apart from never driving in reverse again, what can you do to make sure the spiral bevel gears on your pinion shaft and front output shaft don’t explode? In order to save your transmission, you need to upgrade. Upgrading your gears, your case, and your snorkel bearing retainer ring are surefire ways to make sure your transmission can handle the kind of riding you like to do.
SuperATV has an upgraded transmission case built with more material around your spiral bevel gears to keep them from pulling apart. The transmission case has extra ribbing throughout that makes it stronger and acts as a heat sink to keep it cooler. It’s a straightforward and effective way to reduce failures.
To really make your transmission bulletproof you’ll want SuperATV’s heavy-duty pinion shaft and snorkel gear kit which includes a heavy-duty pinion bearing retainer ring.
SuperATV has gone to great lengths to make sure their snorkel gear kit is a perfect fit, runs smoothly, and is made stronger. First, we use 9310 steel—which is a high-strength gear alloy—to make our gears. It’s the same gear material used in NASCAR vehicles. There’s nothing better out there, and it’s a major upgrade from OEM.
The smoothness of two mating gears has to do with meshing, primarily. When two gears mesh well, they are positioned perfectly. Perfect positioning allows the teeth on each gear to roll over each other smoothly and make contact over a large portion of each tooth. Good meshing requires the teeth of each gear to have the right amount of spiral and perfect angles on each tooth. If the gears mesh just right, you’ll hardly be able to tell that there are gears rubbing together at all.
It’s not easy making making a high-quality pair of gears. They’re perfectly designed using cutting-edge CAD software and then meticulously machined. Before they’re finished, we use a process called lapping to run two mating gears together until they’re broken in. That means the gears we send in each of our kits have even better meshing than OEM gears.
After all that, we stick them on our testing machine and see how well they mesh. This process involves slathering the gears in yellow grease, then running them together until a mesh pattern appears. Basically, the more grease gets cleaned off the tooth, the better the mesh. We tested out several configurations during R&D and you can clearly see the difference between a good mesh and a bad mesh.
Investing in your transmission is just that: an investment. Getting better parts now will save you time and money down the road. But when it comes to getting something better, make sure you actually know what makes it good before risking your ride on it. At SuperATV, we don’t guess and we’ve got an unbeatable snorkel gear and pinion shaft kit to prove it.