Farmall Super M wont go into 4th and 5th Gear

Last Fall I posted on here that my Farmall Super M tractor would not move after a cold spell. Thanks to the help on here, I found it was full of ice mixed with the oil in the tranny/rear end. After melting the ice, I drained it, cleaned it, and replaced the oil. That solved that problem.

However, just prior to that cold spell, I was driving down the road and was using 5th gear. I had to downshift for a hill. After that, I could not get it back into 4th or 5th gear. When I got home, I removed the shift lever and found the three slide rails were aligned as they should be. (Note: Earlier on the year I had the tip of the shift lever built up at a machine shop, because it was worn and occasionally would cause the slide rails to become misaligned).

After changing that fluid, I found it still would not go into 4 th + 5th gear, but it was too cold to mess with it. Now that the weather has warmed up, and the fluid level is up to snuff, I took it for a drive, got it nice and warm, and still it would not go into those gears. It works fine in Rev 1 2 and 3.

The shifter does go into the knotch, but I can not move the shifter back or forth. I tried to push and pull really hard, and even tapped (lightly) on the shift lever with a hammer. I wont go into those upper gears at all.

Anyone know what could be wrong?

PS. I made a boot out of an old tractor inner tube and a hose clamp and put it around the shift lever to prevent water from entering the gear lube again!

Thanks for all help in advance...

* Farmall Red *

The rails can become rusted tight. Forcing them is usually going to bend a component. If the tip of the shifter is too thick Left and right, it could be hanging up on the 2-3 rail. to check this see if it can be shifted into gear with the lever out, and using a little pry bar. (clutch blocked down is helpful) If it does move, thinning the tip might be in order. Jim

I had to weld up my shift lever too,i just took a hand file and trimmed it up, 2nd time it worked good. But i think like Jim said u have a rust problem, Unless you have a cherry picker, its best if you have one extra hand there to help lift the top cover off!

(quoted from post at 23:30:03 03/13/15) The rails can become rusted tight. Forcing them is usually going to bend a component. If the tip of the shifter is too thick Left and right, it could be hanging up on the 2-3 rail. to check this see if it can be shifted into gear with the lever out, and using a little pry bar. (clutch blocked down is helpful) If it does move, thinning the tip might be in order. Jim

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Thanks for the advice. However, I can not understand how the rails could suddenly "rust tight". As I said, I was using 4th and 5th gears. I had driven 2 or 3 miles using them. Suddenly they stopped working. I downshifted for a hill, and when I was past that hill, I could no longer get the shifter into 4th or 5th.

I will try to shift it with the lever out. That maks sense!

I agree, sudden rust-seizure is unlikely.

What is more likely is that when you downshifted for the hill, you bent the 4-5 shift rail.

Unfortunately you are going to have to lift off the transmission cover and investigate the problem. This is not something you can "adjust away" or fix with some "magic potion.'

Could try removing the belt pulley gear box or hole opening cover to look first. You can see the 4th and 5th sliding gear and the end of the shift rail. Gear should wiggle just a little on the shaft if free and the shift rail should wiggle a little side to side if free. If the shift rail is stuck in the neutral position but gear is free you could try knocking of pushing the forward rail end back. Or maybe locate the problem before removing the complete top.

Yes, the top cover is a pain to get off. But it's better than having to split the tractor.

If the rails are still in alignment then the detent ball and spring could be inverted, or if the wrong size ball is used sometimes they won't shift. To big it will not set in gear and to small they keep it from shifting. If you used a bolt for the lever with a head on it that can keep it from moving enough to get the side rails.

On second reading, I agree No rust issue (or only a rusty broken detent spring that broke and jammed the rail) If it does move into position with the lever out, using a pry bar, It is likely the shifter, or as Identified by Caterpillar Guy, the pivot pin at the top of the tower limiting travel into the 4-5 notch. Jim