I picked up a new (-ish; 2008 420FM Rancher). Runs fine, doesn’t have 4th gear. First through third seem fine, but fourth is nonexistent (sorry, didn’t check what happens at fifth.) Before you lecture me on the wisdom of this purchase, don’t. Deal’s done, and nothing you can say now will resound any louder than the experience I will derive from the situation I have just put myself in. I think it will work out just fine, but check with me in a year to be sure.

Anyway, my thought is: I need to buy a new transmission. More specifically, I plan to search on ebay for a "Honda Rancher 420 transmission" that fits an 07 or 08 Rancher, then buy the cheapest one that comes up and put it in.

Are there any flaws in this reasoning? Is there a chance transmission is not the issue? Do I need to run any more tests?