What is a Jackshaft on a Snowmobile? [+Greasing Guide]


The jackshaft on a snowmobile is the shaft that connects the driven clutch with the chain drive gear. The driven clutch drives the jackshaft while the jackshaft drives the gear in the chaincase.

If you want to learn more about a snowmobile’s jackshaft, you are in the right place.

We’ve compiled the most important info on this key part and its maintenance under one roof.

From jackshaft lubrication to bearing replacement, we have it all covered!

What is a Jackshaft on a Snowmobile?

Simply put, a snowmobile’s jackshaft is a long metal shaft that runs across the sled. It transfers the power from the clutch to the chaincase. Let’s take a closer look at where the jackshaft is located in a snowmobile’s drive train:

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

Let’s take a brief look at what the jackshaft looks like (from the chaincase side):

Snowmobile Jackshaft vs. Driveshaft: What is the Difference?

Are you wondering what the difference is between a snowmobile jackshaft and the driveshaft?

The jackshaft takes the power from the snowmobile’s secondary clutch to the chaincase, while the driveshaft transfers the power to the track from the chaincase. This means that if you remove the chaincase cover you can see both of these shafts. The upper shaft with the smaller gear on it is the jackshaft, while the lower one with the larger gear is the driveshaft.

Confused?

For a better understanding, please take a look at this basic picture of a snowmobile drivetrain:

Snowmobile drivetrain

How do you Grease a Snowmobile Jackshaft?

Snowmobile jackshaft lubrication is the type of maintenance that is often overlooked, which can result in faster wear and tear. Keep in mind that it’s much cheaper and easier to periodically grease the bearings than to replace them! Moreover, improper lubrication can lead to lots of other damage as well.

Thus, you may want to know how to lubricate a snowmobile jackshaft.

To grease snowmobile jackshaft bearings, you have to remove the secondary clutch, the chaincase cover, and the gear from the jackshaft as well. This is because there are bearings on both ends of the jackshaft! Before removing the chaincase cover, make sure you first drain the chaincase oil! Grease the bearings with proper lubricant, reinstall every part, and finally fill the chaincase up with fresh oil.

There is an easier way to grease the bearings without removing them. The drawback of this solution is that you can’t grease the other side of the bearings.

Snowmobiles usually feature sealed jackshaft bearings, which are harder to grease. This is because you first have to remove the plastic seal to grease them properly.

But don’t worry, as it’s not rocket science:

If you want to know how to remove snowmobile jackshaft bearings, keep reading!

How to Remove the Jackshaft from a Snowmobile

Removing the jackshaft bearings usually means you have to remove the whole jackshaft.

To remove a snowmobile jackshaft, you have to first remove everything on the chaincase side: cover, gear, snap rings, and washers. Then, remove the secondary clutch and the snap ring on this side as well. Applying some heat on the bearing seat can help you remove the shaft more easily. Finally, grab the end of the jackshaft and pull it out by hand. If it’s stuck, you can carefully help it out with a rubber mallet.

You can see the process in this tutorial video:

Beware that the way to remove the jackshaft from a sled may vary from one model to the next. Always refer to your sled’s service manual before you start to remove the jackshaft.

How do You Replace Jackshaft Bearings on a Snowmobile?

Many say that once you’ve pulled the jackshaft out, it makes sense to replace the stock bearings with higher quality aftermarket ones.

To replace the jackshaft bearings on your snowmobile, you have to first purchase the replacement parts. They typically come in a kit that contains the jackshaft bearings (chaincase and outer bearing), O-rings, seals, and any other components that may be required. Remove the jackshaft as described above, then reassemble with the new parts.

Place the bearings into the freezer for a while. Then, you should again apply some heat on the bearing seat. Before you install them, make sure that the bearings face the right way!

To replace them, you can use a short aluminum pipe with a diameter of about 2” and a hammer. The bearings should go into place after some gentle taps:

Conclusion

The jackshaft is a key part of every snowmobile, as this transfers the power from the clutch to the chaincase.

Be careful not to confuse the jackshaft with the driveshaft. If you remove the chaincase cover, the jackshaft is the upper one with the smaller gear on it, while the larger gear is found on the driveshaft.

Snowmobile jackshaft lubrication is a very important type of maintenance, so don’t overlook it!

The jackshaft turns nearly as fast as the engine RPM (or even around the same RPM at full speed), so a lack of lubrication can lead to many issues.

Paying attention to your snowmobile’s jackshaft and bearings is like cheap insurance!

To grease the jackshaft bearings, you have to remove the chaincase and the secondary clutch as well. That’s why it’s recommended that you handle this maintenance task when you change the oil in the chaincase.

This is because you have to remove the chaincase cover to access the jackshaft bearing, which is not possible without first draining the chaincase oil.

Disclaimer: This post is for informational purposes only! For exact maintenance steps always refer to your sled’s service manual, or ask your dealer for further advice!

References:

https://totallyamaha.com/snowmobiles/aaTECH/Jackshaftreplace/Jackshaftchange.htm

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