It would be very difficult to provide much advice by just reading your summary of the problem. I can let you know that 3rd gear was always a problem on our 50. We made a small wooden wedge and inserted in the shifting grid to hold the shifter from slipping out of gear. Still today, 66 years later, without the wedge it will periodically slip out of gear.

Freeway said:

So my dad (82 years old) borrowed his JD 50 to a neighbor/friend who wanted to cultivate a small field. Apparently, it kept popping out of 3rd gear, so the neighbor put a crescent wrench in place to keep it from popping out of gear. My dad can't explain to me what actually happened, but now you can put the tractor into any gear on the left side of the shift pattern, but the tractor will not move. If you try to put it into gear on the right side pattern, it will not go into any gear.

I am going home for a visit on Easter and my brother and I will likely at least see if we can figure out what the problem may be.

Any suggestions on where to start/look? My brother and I are both aircraft mechanics, so have mechanical backgrounds, but not familiar with tractor drive trains. Specific locations of panels to take off/investigate would be very helpful and much appreciated.

Thank you! Kevin

Click to expand...

My experience is with a late JD "B" tranny which is very similar to the model 50. One of the possibilities for jumping out of gear is the detent spring on that shift rail is weak or broken. Or the notch in the rail is damaged. Could be several other things, I'm sure, but this may be the most common.
Maybe the ball on the end of the shift lever has broken off. I believe it would be possible to position it in any of the 3-5-6 notches, but would not actually move any shift forks to move a gear. Trying to move to the 1-2-4-R side involves the shift lever end moving the low/high range fork. If it doesn't move it won't allow the shift lever to lock into any of the "lower range" positions. These are just my best guesses as to what may be wrong. The problem I was working on with the B, was rusted shift forks/rails, and rusted sliding gears and shafts. Couldn't shift anything. Had to disassemble the tranny to do this, plus replace some parts and all bearings. Not fun, but challenging. lol

A side note for those who have one jumping out of gear: for safety purposes, it might be better to put a wedge into the gear quadrant slot to keep anyone from using that gear. It can be dangerous if they jump out of gear, to the transmission, as well as the operator, until it can be repaired completely.

It will be very beneficial to get a Service Repair Manual for the 50 before starting the repair, as you don't at this point know how far you might have to tear it down. The B is somewhat different than a 50 in the dash and steering rod support, but you need to start there to remove the shift quadrant, shift lever, etc. If the ball end of the shift lever is broken off, be sure you find all the pieces. If it is broken, it was probably caused by the gear trying to jump with only the lever holding it. The shift lever pretty much just moves stuff around, but not the intended locking device. Replacing detent springs or buttons requires removal of the clutch, first reduction gear cover, flywheel, and 4-6 shifter cover, to name a few. A 50 has some additional parts due to the wonderful live PTO that a B only wishes it had.
Keep us posted on the progress!

tommyhawk

Here's a pic of what you will probably see when you get the tranny shifter cover off. This is a 1950 B. I suspect the model 50 will look very nearly the same.


The upper fork is the hi/low shifter. It is almost aligned to the hi side (3-5-6) fork openings. Notice the forks that have a button sticking up. The spring is inside the fork holding the button in the notch in the shaft (rail) to keep it engaged. The rod for the bottom fork has a much different button with the spring at the top and the button in the case. The spring is just visible in the left side of the pic. The cover plate compresses that spring.
When you reattach the shifter, the manual will recommend how to position the forks and the lever. This one was about to be assembled, with all shifted to neutral.
Hope I'm getting all this right. It has been several years since the hands on with this tractor. Looking at the picture and thinking how the bottom of the shift lever is in relation to the top part where you move it is a little tricky. Kinda upside down and backwards? Much easier to understand when you can touch the parts and watch what they do.

tommyhawk

thanks for your reply, seems this may have been a common problem. Enjoyed reading the story : )

Trebor said:

It would be very difficult to provide much advice by just reading your summary of the problem. I can let you know that 3rd gear was always a problem on our 50. We made a small wooden wedge and inserted in the shifting grid to hold the shifter from slipping out of gear. Still today, 66 years later, without the wedge it will periodically slip out of gear.

Click to expand...

Thanks for the very detailed information and the picture, gives me an idea of what to expect when I get it opened up. Will likely be searching for a manual and will post what I find if I get it opened up this weekend. Thanks for taking the time out of your day to answer my post! Kevin

tommyhawk said:

Here's a pic of what you will probably see when you get the tranny shifter cover off. This is a 1950 B. I suspect the model 50 will look very nearly the same.

View attachment 780868
The upper fork is the hi/low shifter. It is almost aligned to the hi side (3-5-6) fork openings. Notice the forks that have a button sticking up. The spring is inside the fork holding the button in the notch in the shaft (rail) to keep it engaged. The rod for the bottom fork has a much different button with the spring at the top and the button in the case. The spring is just visible in the left side of the pic. The cover plate compresses that spring.
When you reattach the shifter, the manual will recommend how to position the forks and the lever. This one was about to be assembled, with all shifted to neutral.
Hope I'm getting all this right. It has been several years since the hands on with this tractor. Looking at the picture and thinking how the bottom of the shift lever is in relation to the top part where you move it is a little tricky. Kinda upside down and backwards? Much easier to understand when you can touch the parts and watch what they do.

tommyhawk

Click to expand...