I hope to the Snow Gods that there is a better way now, but this is how I've been changing my chain case oil for years.
First, what a cover from an '86 Trail looks like. The one on the 400 is the exact same thing.

Note that there are two circled spots. One is the filler, and the other a drain check.
Slowly remove the cover for the oil to spill out everywhere. Eventually it will look like this:

From here bolt the cover back to the chaincase mechinism (sp). While leaving the botton screw out(half assed circled) pour chain lube in to the filler hole...

"HUH? You Want ME to do WHAT???"
Oh, it helps if you have a clever home made funnel. Like this one:
and this.....

Put the home made funnel in the filler hole and pour chain lube in the funnel slowly. Fill until oil starts to come out of the lower hole.

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One thing to help the mess is, drill a hole in your belly pan and then put a drain pan underneath the sled and let the oil drain out that hole.

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Why dont you just drill and tap a hole in your chain case and install a drain plug. Ive done it on several sleds and its faster and less of a mess.

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Hmmmm, I never thought of that. I wonder why the engineers at Polaris Industries didn't come up with that idea before I bought these two machines.

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^^^less trips to the dealers for work means less money for them, we cant have that now, lol...

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