When servicing my sled for the season, I pulled the chaincase cover and discovered the chain had some plates that were broken. When I went to my dealer to order a new chain, he told me I’d be stupid to not replace the gears as well. I wonder of he’s just trying to get me to buy more parts that I don’t really need. What should I do?
Your dealer is being pretty straight with you. Just like the drive chain and sprockets on a motorcycle, you ideally should replace them all as a set. When put into service, the parts all mate and match to each other. Putting a new chain on old gears will wear out the chain far faster than it normally would.
Most importantly, everyone should be removing the chaincase cover, draining the old lube, inspecting the chain and gears for excessive wear and install fresh lube. Just like you were. In the shop at your convenience is far better than having a failure out in the middle of a great ride. Been there, done that. Getting towed in 60 miles in no fun.
And, just like a chain on a motorcycle, they will stretch and reach a service limit over time. So, even if the chain isn’t visibly damaged, as they get older you want to measure them and compare to the service limit as specified in the service manual. Usually, this is done with the chain installed and under tension, and will be a maximum spec for the distance between a certain number of pins.