What Does the Chaincase Do On A Snowmobile? [Diagram]


The chaincase is a part of the snowmobile’s secondary drive system, that houses the chain and the sprockets. Simply put, this feature is an intermediate gear reduction drive system, which transfers power from the transmission to the track. Also, these parts provide the necessary gear reduction between the track and the transmission (CVT).

If you want to learn more about a snowmobile’s chaincase and its maintenance, this post is for you!

What Does the Chaincase do on a Snowmobile?

First, let’s see in a nutshell what a chaincase does on a snowmobile:

Confused? Let’s see step-by-step how the power is transferred from the engine to the track!

Engine > Drive clutch > Belt > Driven clutch > Jackshaft > Chain drive gear > Chain > Chain driven gear > Drive shaft > Track drive > Track

You can see a simple sketch of a snowmobile drivetrain in this picture:

Snowmobile chaincase
Snowmobile chaincase

How Does a Snowmobile Chaincase Work?

Surprisingly, the snowmobile chaincase works in a very similar way as the chain and sprockets on motorcycles. Without the chaincase, a snowmobile’s track would spin as fast as the engine’s RPMs! That’s why the snowmobile chaincase houses a chain and two sprockets of different sizes. The transmission (CVT) drives the smaller sprocket, which drives the chain. Finally, this chain rotates a much larger sprocket with about twice as many teeth.

Snowmobile engines can reach 8000-9000 RPMs, which would be too fast for the track. That’s why the RPM need to be significantly reduced by the chaincase.

If you want to learn more about how a snowmobile chaincase works, don’t miss this informative video:

What is Chaincase Oil?

Chaincase oil is a lubricant that can be found in snowmobiles’ chaincase. As the chain and the sprockets in the chaincase rotate very fast, they need to be properly lubricated. Chaincase oil not only makes these parts “slippery” for easier rotation but reduces the wear on them as well. Are you wondering which snowmobile chaincase oils are the best on the market? Keep reading!

What Kind of Oil Goes in a Snowmobile Chaincase?

Snowmobile chaincase oils are special synthetic chaincase lubricants exclusively formulated for snowmobiles. That’s why it’s not recommended that you use other types of oils in your chaincase. Other oils don’t provide proper lubrication for the chain and the sprockets. Moreover, they are prone to expanding if you ride your sled at high speed. This can result in more wear and tear, or even damage!

Because of these risks, always only use OEM chaincase oil in your snowmobile. Chaincases contain a very small amount of oil, so it doesn’t make sense to use anything else!

Let’s check which brands are recommended OEM chaincase lubricants.

OEM Snowmobile Chaincase Oils by Brand

Polaris Chaincase Oil: SCL Synthetic Chaincase Lubricant

Arctic Cat Chaincase Oil: Arctic Cat Synthetic Chain Lube

Ski-Doo Chaincase Oil: BRP Ski-Doo XPS Synthetic Chaincase Oil

Yamaha Chaincase Oil: Yamalube Snowmobile Chain Case Lube

What weight is snowmobile Chaincase oil?

The weight of snowmobile chaincase oils are typically 75W-140 and 75W-90. But even if many aftermarket chaincase oils are available on the market, it’s recommended that you only use the oil described in your sled’s manual. It’s also important to not mix different types of oils!

How Much Oil Goes in a Snowmobile Chaincase?

The average oil capacity of snowmobile chaincases is about 8-11 ounces depending on the make and model. The required amount of oil also depends on the size of the chain and the sprockets. When you change the oil in the chaincase, you can usually take out about 8-9 ounces. If your sled’s chaincase features a dipstick, you can easily check the oil level with it. If not, you should add oil until it begins to overflow (“Fill to spill!”).

When Should I Change my Chaincase Oil?

According to major manufacturers, you should change the chaincase oil on your snowmobile once a year or after 2000 miles, whichever comes first. Best practice is to change the chaincase oil on your sled at the end of each season. Additionally, if you have a new sled, don’t forget that you have to inspect or even change the chaincase oil after the first 300-500 miles.

As the required maintenance and intervals may vary from one sled to the next, don’t forget to check your sled’s manual for further information.

There are three main reasons for periodically changing the chaincase oil:

  • Because of several heating and cooling cycles, the oil breaks down.
  • Oil may get contaminated by metal particles from the gears and the chain.
  • Water can get into the oil by adsorption. This can lead to corrosion during the off-season!

How do You Change the Oil on a Snowmobile Chaincase?

To change the oil on a snowmobile chaincase you will need about 10 ounces of fresh chaincase oil. Drain the used oil from the sled though the drill hole or the fill hole with a manual oil extractor. Pour fresh oil into the fill hole until it starts to overflow. If your sled’s chaincase features a dipstick, don’t forget to check it also. Finally, replace the fill plug and clean everything up.

You can change the oil on a snowmobile chaincase using these simple steps:

  1. Ensure the sled is on a flat surface.
  2. Set the parking brake.
  3. If your chaincase features a drain plug, remove it and wait until all of the oil comes out.
  4. Replace and tighten the drain plug.
  5. If there is no drain plug on your chaincase, you should remove the fill plug.
  6. Grab a manual oil extractor and insert its tube into the fill hole. Push it toward the bottom of the chaincase, but try to avoid the chain and the gears.
  7. Extract as much oil as you can.
  8. Pour the fresh chaincase oil into the fill hole with a funnel. Place a small rag under the funnel and the hole to catch the drippings and overflow.
  9. You can check the oil level with the dipstick. If your chaincase doesn’t have one, you have to fill the oil up until it starts to run out of the fill hole.
  10. Clean the area with a rag or a shop towel.
  11. Clean and replace the fill plug.

If you want to inspect the chain and the gears, you can do it before you pour the fresh oil into the chaincase. To do this, just remove the chaincase cover once you’ve drained the used oil.

FAQs About Snowmobile Chaincases

How much oil goes in a Ski-Doo Chaincase?

The oil capacity of Ski-Doo chaincases are around 8-10 ounces. That’s why the OEM Ski-Doo chaincase oil (XPS Synthetic Chaincase Oil) comes in a 12-ounce bottle. This quantity is plenty for any Ski-Doo’s chaincase.

How do you change the oil on a Polaris chaincase?

To change the oil on a Polaris chaincase, you will need a manual oil extractor. As Polaris snowmobiles usually don’t feature drain plugs, you have to siphon the used oil with this pump. Another trick is to loosen the bolts on the chaincase cover and let the used oil flow out, as you can see on this video:

Chaincase oil vs. gear oil – what is the difference?

The chaincase oil vs. gear oil debate is a well-known argument among sledders. Some say that gear oils can be used in the chaincase, while others claim that the best practice is to stick to special chaincase oils. What is the truth?

It’s a fact that gear oils are generally too thick for chain drives, especially in cold weather. This may end in improper lubrication, or even damage to the chain or the gears. Therefore, best practice is to only use OEM chaincase oils every time!

How tight should a snowmobile chain be?

According to some sleds’ service manuals, the sag of the snowmobile chains should be around 1/8″. If you want to know how tight the chain should be on your snowmobile, you can find it in your sled’s service manual. Additionally, don’t miss this informative tutorial video on how to tighten the chain on your sled:

How do you remove the chain from a snowmobile?

You can remove the chain from your sled if you follow these 6 simple steps:

  1. Install the parking brake
  2. Drain the oil from the chaincase
  3. Remove the chaincase cover
  4. Remove the bolts from the gears
  5. Loosen and remove the chain tensioner
  6. You can remove the chain and the gears together

You can see the whole process on this video:

Conclusion

A snowmobile chaincase accommodates two gears and a chain. These parts are designed to reduce the engine RPM.

To lubricate the chain and the gears, the chaincase is filled with 8-10 ounces of synthetic chaincase oil.

Just like engine oil, chaincase oil also has to be changed every year. Best practice is to change it immediately after the season.

Manufacturers recommend only using OEM oils for your sled. Aftermarket chaincase oils, gear oils, engine oils, or any other lubricants are not recommended.

Changing the oil in a chaincase is very easy, as there is a drill hole on the bottom of most sleds to drain the used oil out. If your sled doesn’t have one, don’t worry. You can siphon the oil out with a manual oil extractor, or you can loosen the bolts on the cover to let the oil flow out.

Finally, pour the right amount of fresh oil into the fill hole.

This is our short snowmobile chaincase oil change guide. We hope you find it useful!

Disclaimer: The post is just for informational purposes. Always read your sled’s manual carefully before any maintenance!

References:

https://www.henkel-adhesives.com/us/en/insights/all-insights/blog/change-snowmobile-chain-case-oil.html

https://www.ski-doo.com/community/ontrack/mid-season-maintenance.html

https://snowmobiles.polaris.com/en-us/self-help/article/KA-02117/

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