http://www.searspartsdirect.com/partsdirect/getSubComp.pd?modelNumber=917273404&productCategoryId=1509200&brandId=0247&brandDescription=CRAFTSMAN&modelName=LAWN-TRACTOR&diagramPageId=00001&componentDescription=PEERLESS%20TRANSAXLE%20-%202000-006A&documentId=P0107012&blt=06 If that picture comes up, you'll see the gears in your transmission. You'll see that some of the gears meet at a 90 degree angle. That's probably where your problem is; they are no longer meeting. You can probably repair these yourself, but it's time consuming.

there is no need to remove the transmission just remove the gears that engage the gear in the wheel.

You probably have nothing to lose if you clean it up and open to have a look. Normally Honda doesn't service internal trans parts, but maybe you will luck out.

I have an MTD rear tine roto-tiller and had an issue with my tines disengaging with the slightest bit of resistance. I pulled the transmission gear box assembly apart and found that one gear, shown in the attached photo, and indicated with an arrow had a key slot that was badly worn. This was allowing the tines to disengage. I took it apart and flipped the gear over as the other side of the gear keyway was fine. I put everything back together as shown in the photo and it runs fine now. I