need help with Cockshutt 30 transmission assembly

When I restored my Cockshutt 30 last year I screwed up. I split the creeper gear case from the transmission in order to install the live power take off shaft into the creeper gear box. (I converted a standard pto tractor to live power take off). Those parts went in fine. I bolted the creeper case back to the transmission and started and drove the tractor a bit.
Yesterday the tractor jammed in reverse. I could not get the tractor to move. So I pulled the gear shift cover off the tranny and saw the problem. The shaft on which the reverse gear slides had moved backwards and allowed the gear to almost fall off. I carefully removed the reverse gear and went to my parts book to see what is missing to prevent the shaft from moving forward again. The parts diagram shows a "woodruff key" that goes on the front of the shaft. So I searched thru my spare parts box and lo and behold I found what I call a half moon key with a note I put on it, "fell out from between creeper case and transmission".
So, Q1/---how does that key fit on the end of the shaft to secure it?
Q2--- do I have to separate the creeper gear case from the transmission case to put that key in place somehow? (I am hoping there is an easier way that splitting the tractor again).
I attach a pic of the shaft with the notch in it, I presume for the half moon shaped key.

Here is a pic of the key that I think goes on the end of the shaft somehow.

That half-moon is a woodruff key. It looks like there is a slot barely visible in the small end of the shaft for the key but it has to engage the case wall. Take the cover off the creeper case under the battery box. You may see where it goes but I think the key may be sandwiched between the two case walls. Could have fallen out when you split it and you missed putting it back in.

I did the same thing. Instead of splitting the tractor I just put a flat on the pin and drilled/taped the casting for a bolt to hold it in.

Mike, I did remove the creeper case cover to look inside. The creeper case has a hump where the end of the shaft is, basically it covers the end so you can"t get at it. Looks like the key is sandwiched between the two cases and to do it like they wanted at the factory, I"d have to split the cases apart.

However, I like the first idea of drilling and tapping the transmission case for a bolt that goes down into the reverse gear shaft. But I guess I"d have to drain the oil as there will be shavings getting pulled out of the hole as I drill. Don"t see any other downsides to that fix, unless drilling a hole weakens the case there. Thanks for the advice guys.

I'm going to remember that key when I get to doing mine over.

You can also put grease in the flutes of the drill and the shavings will tend to stick in the grease.

If you decide to drill that boss for a screw I would locktite it or wire it to be sure it wouldn't work loose. You could form up a small pan from aluminum foil under the boss to catch the chips and keep them off the gears and shaft.

I"ll complete this thread by describing my ultimate repair.
I decided to split the tractor instead of drilling and taping as I am not that good at it.
You don"t have to separate the tractor that much. I took the lock nuts off the studs in the trans and put the nuts back on the first couple threads to prevent the tractor from splitting apart more than about an inch. With a floor jack under the drawbar front pin, and a bottle jack under the center of the tractor, I gave a good pull and she separated to where the nuts prevented it from coming apart further.
Push the reverse gear shaft forward until you can see the slot. Turn slot facing up. Put grease on the woodruff key, all sides, and with a pencil magnet drop it into the slot. Then carefully turn the shaft clockwise so the key is on the RH side (without grease it would fall to the floor). Then push the shaft forward and the key will fit into a round depression in the creeper case. Hold shaft in that position and bolt the tractor back together.
Not really that bad a job. Only have the drain the back half of creeper case. No need to drain transmission. Tiny bit of oil leaks out during the repair, but not much.
One final note. I found a service manual printed in the mid 50"s. It said the CK 30 prior to serial 25555 used a woodruff key to hold that shaft, but after 25555 they drilled that boss in the trans, installed a bolt, and wired it in place.
Thanks for all the advice guys. Got her done and I"m happy.