Trans knock downhill

Recently got 2 farmall sc from my grandfather. Both run but seem to have there own personalities. As i am new to these but enjoy working on old cars/equiptment i have many questions. One tractor makes a light knocking you can hear and feel only when on a downhill. Dont want to do any damage to a pretty good tractor. Any ideas what it might be or where to check. I assume something in trans.

The noise reminds me of the sound the oil slinger makes wjhen it about to trash itself. It could be a chipped gear on the coast side, that happens as well. The oilslinger is aluminum, and is used to lube the trans when using the tractor stationary, as the top shaft needs to be oiled when the bottom (lay) shaft rear section is not moving, as PTO or Belt work. Jim

Thanks for the help. How should i check guessing the only way is to open up the trans. or hopefully something not so major. Any tips. Please bear with me this is all new.

There is also a chance there is a tranny bearing going out. I had one let a shaft wobble when unloaded like that. Made a knocking sound. Either way, gotta pull the top.

pulling the top off is not too tough. it is all visible from their. Jim

Either way you look at this you are headed for a split. May as well get in there and start looking around, you'll find what's knocking. Once it is split in half, you can try putting in Neutral and spin what will spin but your probably gonna need to Jack up one or both back tires and spin them with the transmission in gear and look and listen for your clunk. Probably gonna find it'll be a bearing or chipped tooth. Look around good, I had both in one tractor. The roller Bearing cage failed, one of the rollers fell out, got kicked over to a $600.00 gear and chipped the tooth. Funny how a $20.00 part can run up a tab! Well not real funny.
Best way I found to crack most any Farmall is to support the front half at the rear portion of it, so you can just push it to the other end of the garage when its unbolted so its out of your way. Block up the front of the rear half and get to work.
A few tips also is keep things covered so no dirt gets inside your reservoir. Not real sure about your tractor but if it has a seal between the two halves to seal the fluid suction line, REPLACE IT, trust me. Other than that, its really not a bad job to do, once your done you'll realize it wasn't so bad.
Good luck,
Tod Michigan

Well hope it doesnt come to breakin it allthough it would make for a good winter project. we'll see Thanks all