Hello and thank you for any insight I may gain.  Yesterday while pulling my spring tooth transmission started to make ugly noises under extreme load. It has always had problems staying in 2nd gear without a wooden shim wedged in shift gate but no other problems, limped it back to shop to discover it will not  stay in reverse enough to back up. I discover tranny is full of water. Drain was going to wash with diesel while cleaning out bung area with my fingers I find this spanner type nut in the bottom of  pan see photos. Anyone know what this is and where it came from, and of course what next, Thank You I am a little confused about posting pictures but here it goes

If your shift lever boot is bad, rain can seep in there.

     

That is required to hold the main input shaft and parts together, kind of serious that it came off (a little important), part number should be 2B 3560 should have a ring to help hold it in place from coming loose, guessing your clip would be close to where you found the nut or rusted to pieces if filled with water.

to get any kind of access to this problem i will have to take tranny cover off?

I believe so,

buy paying the membership fee will i have access to exploded photos of this transmission

Yes you will, and it's probably the cheapest form of manual access you'll find, short of already having them in your possession. Next steps, remove the fuel tank/seat, remove the transmission top cover, drain the transmission and flush it down and inspect. I would suspect you might be up for a set of bearings which are very cheap compared to broken gears, shafts, etc. Recommend that you take this opportunity to refurbish the transmission thoroughly with bearings, seals, locking washers, gaskets. With your serial number, this is a relatively straightforward task

There should be a parts listing in the technical library for members. We would really like to have you as a member so in the meantime here is a scan from my parts book for 7u-1 and up.

That is part # 2B3559 - nut. There is a ring, part # 2B3560 that acts as a lock for the nut.

The top cover has to come off and you will have to remove the entire clutch pack. There is a special socket that will engage that nut, but you may be able to tighten it by other methods.

The lock ring needs to be exactly lined up to engage the shaft. If there is other damage, the pinion shaft will have to come out - from the top front. The lower shaft will not come out from the front but must be removed from the rear. If you have a Hyster winch on the tractor, that will need to come off before the lower shaft can be pulled.

This is a big job

      O K today got seat fenders linkages removed soaking in diesel will pressure wash tomorrow and try to remove cover.
is it possible to take out clutch assembly without pulling engine ?
while flushing i discover a thick washer 1/4" thick wth a tapper on one edge layin in pan .
here are sum photos maybe