Super M locking in !st and 3rd

I have a Super M that is seemingly locking in first and reverse. The first time it happened I was able to wiggle the shifter after I had shut it off, and free it up. This last time I haven't been able to. I was able to drive it in 3rd, 4th, or fifth, and thus was able to get it out of the woods. I have been reading old posts about pulling the shifter and realigning the forks. I intend to try this, but I'm wondering if the fact that I also have problems with the right brake locking up might be somehow related to this problem. Additionally, I get a clunking sound that sounds like it's in the right rear wheel, but there doesn't seem to be anything that could clunk.

There is a sloppy shifter kit on Ebay that is getting a lot of praise on here. The tip needs to be builtup as described in the archives. Jim

The clunking could be loose rim clamps. That is the clamps that clamp the rim to the hub. You are going to have to pull the shift lever out to fix your shifting problem. Buy the sloppy shifter kit that is sold on E bay. To get the shifter out, drill a hole in the plugs that cover the retainer pin that holds the shifter in the transmission top cover. Then drive out the pin and the shift lever will come right out. You can then line up the shifter rails so the transmission is in neutral. If the end of the shifter is worn, you may have to build up the end by welding to get things working again. I'm trying to figure out how it would work in 3rd 4th and 5th. When this happened to me, The only gear I had was reverse and it was stuck there. Any other gear and it was in two gears and would not move.

You would NOT have been able to drive the tractor home in 3rd/4th/5th if it were "locked" in 1st or reverse, unless you broke something.

The lock happens when one fork is still in gear and you select another gear at the same time. The transmission binds up, and you're done until you get it out of gear.

Not sure what's really going on in there.

The 1-R rail might be just out of place enough to block the tip, but not in gear. Jim

!st, thanks guys for responding to my post. This is my first time participating on a blog.
It was definitely locked. If I let the clutch out in 1st, reverse, or neutral, the engine stalled. But I was able to drive in all the other gears...I tried them all. I removed the shifter as advised, and the neutral slots (if that"s what they are called) were not perfectly aligned, but not really in any gear. I slid the rails back and forth just to see how far they moved because I"ve never been into any transmission before. Then I realigned them to neutral, put the shifter back in and it worked fine.
I did note that there was some wear on the center rail (2nd & 3rd?)
and also the end of the shifter has been previously built up with a pretty lousy weld, and is showing signs of wearing again. I have a welder and can do some build up, but how do you know how much to add, or grind back off?

On a side note, There was some discussion in older posts regarding the mounting of the shifter on the Super M. Someone suggested that there was a 3 bolt shift tower that was easier to remove than the pin and gave better access. Someone else said that the Super M"s didn"t have that 3 bolt tower,that it was cast in to the top plate. I don"t know what year my super M is (Serial# F-7725 GJ) but it has the removable tower.

Re: the wheel shucking being from loose clamps, wouldn"t there be scraping signs on the wheels by the clamps? I looked for that and do not see any.

The pic shows the sizes. from the views you show your slots might allow a slightly larger dimension on the .750 number, possibly .760" to .765" if put into the slots and can work through neutral, I would do it. I found the pic from Neblink, but I don't know who took it.
The trans looks a bit rusty. as such the detent balls and springs can rust, stick, or fail. Using a space heater to warm the trans for a day or two (safely!!!!!) might reduce the moisture, Changing the fluid might be a good idea as well. 85W140 gl4 or gl5 is fine. 85-90 is also good.
The loose rim on the clamps do not often reveal obvious problems. They also often need to be loosened, lubed, and retightened due to stuck threads. Jim