720 clutch...the soap opera continues

Howdy again,

Well, I spent part of the day messing with the old girl again to figure out this issue of coming out of gear while going downhill and then coming back in at the bottom. I tested one suggestion of putting the tractor in 6th and holding the brakes to see if the clutch slipped before it started lugging down. No slippage at all. I then hit the long hill down to the barn to run through all the gears. I thought I had done this already but had not so, sorry if I said I had earlier. 1st gear...started rolling, 2nd gear...started rolling, moved to 4th (on left side of shifter quadrant)...started rolling. I moved to the right side and tried 3rd...no roll. Wait a minute. I moved on to 5th...no roll. Did the same in 6th. On the way back up the hill I tried reverse and there was no roll there either. I thought it had to be in the shifting forks or rails or something so I took it to the shop and proceeded to pull the top cover and have a look. I couldn't see anything odd or seemingly wrong. I went to my shop manual to make some comparisons and do some tinkering. I discovered that my three gears that seem to let go are all tied to the others that don't. Hmmm. Also, two of my rolling gears (2nd and 4th) are positively locked. Meaning that the only way to pull them out of gear is with the shifter itself. I put them in gear and then tried to push them with a pry bar and could not until I unlocked the spring loaded part of the shifter. This throws a whole craftsman toolbox full of wrenches into this mess. Why would only 1st, 2nd, and 4th come out when all of those same shifters work on the other side of the quadrant? It can't be a clutch issue, otherwise all of my gears would do this but my gears can't just pop out either with the positive locking on the shifter rails. Any new ideas would be greatly appreciated. I will keep studying my shop manual to see what I am missing. Got to be something. Tractors can't be possessed....or can they?

Try jacking it up and turning the wheel with the clutch engaged and see what happens. Have you tried actually taking it out of gear while it is going down hill to see if it actually gains speed or stays the same? What happens when you pull the throttle lever way back when going down hill?

Study the over/ under drive shifter. I'd start there. If let's say a top shaft bearing or bearings were loose and the shift shaft loose in the housing (check that these are tight). The over/under drive shift shaft is stationary. If it moves side to side at all, you'll need to remove flywheel and left side cover to access the bolt and nut which hold that shaft in place and provide for adjustment.

If no side play on that shaft at all, then check to make sure the shifter locks in a positive manner both directions. From what I recall, this has a positive lock that will only release when the shifter pushes up on it when moving from high to low or low to high sides. I checked the parts book and if your 720 is sn/ 7202780 and up it has the lock. Under that SN it didn't leave the factory with the lock, but could have been converted.

Hope this helps.

My bet is on the over / under drive coming disengaged...it's still really strange that it kicks back in...but who knows.

Tyler in IL

Sure sounds like it is tied to the over/under drive which is actually a high /low shifter. It shifts when you go from one side to the other of the quadrant. Part of it has small teeth that engage. The other part meshes regular size gear teeth. Take the top off and look at this area. A loose shifting fork and bad bearings and bad adjustment all come to mind. There is not very much of the teeth that engage on one side of this.
Should not be tied to clutch repair unless you also had the first reduction cover off ? You could of lost a spacer washer or snap ring by the little bearing and that would control the position of the input shaft.