The chaincase is an integral part of a snowmobile’s drive system and houses a chain and two sprockets that transfer power from the transmission to the track. Its secondary function is as a gear reduction system, allowing the track to spin at a lower speed than the engine. The snowmobile’s transmission connects to a smaller gear in the chaincase connected by chain to a larger gear within the case that turns the track and propels the sled.
A chaincase serves a similar function to other chain drive systems, like those found on many motorcycles and ATV/UTVs, however a snowmobile chaincase contains the chain drive components in a sealed and removable case. To protect the track’s critical drive components from moisture, corrosion and wear, the chaincase is a closed lubrication system that requires regular oil changes to function correctly.
Chaincase oil breaks down primarily from pressure, heat, contamination by metal shavings from the internal gears and chain, and water from the environment. Snowmobile manufacturers recommend changing chaincase oil annually or every 2,000 miles. It is considered best practice to change the chaincase oil after the riding season is over, to prevent moisture from sitting in the chaincase all summer. The typical snowmobile chaincase requires about eight to 11 ounces to refill and is complete when “filled to spill” or overflowing from the fill hole.
Changing Chaincase Oil
Gather the following tools:
- Oil-drain pan
- Ratchet and correct-sized socket
- Funnel (if necessary)
- Chaincase oil
- Drain the chaincase oil
Locate and remove the drain plug. Examine the oil as it drains. If you notice a silver color, it means the chain and gears have produced metallic particles. This is normal. A chain and gears will generate some metal. However, failure to change the oil yearly allows metal particles to circulate and lead to accelerated wear. That’s why it’s vital to change chaincase oil yearly.
- Replace the drain plug
Once the oil has drained completely, ensure the gasket on the drain plug is undamaged and replace the plug. Check your owner’s manual for torque specifications. If there are none, tighten snugly and avoid over-tightening.
- Add new chaincase oil
Now it’s time to install the new chaincase oil. Remove the fill plug. The location of the fill plug varies depending on your snowmobile. Check your owner’s manual for the location. Position a rag beneath the fill hole to avoid spills. Fill the chaincase. Use a funnel if necessary.
With the sled used in the video demonstration below, the chaincase reservoir is full when oil runs out of the fill hole. Some snowmobile manufacturers specify the amount of oil to install, so check your owner’s manual for the proper quantity. Replace the fill plug and wipe down the area.
That’s all there is to changing snowmobile chaincase oil. It’s an easy maintenance practice that will help you get the most years and best performance from your sled.
Is Chaincase Oil Specific?
Modern snowmobiles and ATVs require extreme-pressure lubricants engineered to meet the high-temperature and high-load demands. Some users believe they can substitute alternate oils in their chaincase to reduce costs.
However, automatic transmission fluid does not contain the extreme-pressure additives needed for enhanced wear protection, leaving gears and chains vulnerable. Likewise, automotive gear lube is too thick for proper chain and gear lubrication in powersports applications, impairing circulation and leading to increased wear and decreased efficiency. Finally, unlike thinner motor oils, snowmobile chaincase oils are typically SAE 75W.
AMSOIL Synthetic Chaincase & Gear Oil is a 100% synthetic formulation that resists shear and chemical breakdown better than conventional fluids, providing superior protection and performance for enclosed chains and gears found in snowmobiles, ATVs and other similar equipment.
It is formulated with extreme-pressure additives for increased wear protection that helps extend chain and gear life and it repels water to inhibit rust and oxidation. Its low pour point ensures superior low-temperature starting and reduces drag to deliver maximum power through the frigid depths of winter. It is engineered for use in all snowmobile chaincases and costs less than most original equipment manufacturer (OEM) recommended chaincase oils.
AMSOIL Technical Writer and 20-year veteran of the motorcycle industry. Enjoys tearing things apart to figure out how they work. If it can’t be repaired, it’s not worth owning.