Rotax C Gear Drive Box Parts Diagram, and Parts Number Listing
how to change the oil in a C gearbox
On top of the gearbox is a breather plug. Remove it.
On the bottom of the gearbox is a drain plug, remove that to drain oil.
When gearbox is empty, replace the drain plug.
On the side of the gearbox are two smaller hex head screws, one about 3-4" above the other.
Remove the BOTTOM screw.
Pour the new oil in the top breather hole until it begins to overflow out of the screw hole on the side of the gearbox.
Torque values are 24nm (212 in./lbs) for the drain plug. 6nm (53 in/lbs0 for the vent plug.
Use gear oil available at any auto parts store. You can use API-GL5, or GL6SAE140EP, or 85W-140EP.
If you have to replace the copper washer on the bottom drain plug, they are also available at the auto parts store.