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I would say the chip is the culprit, based on your description. As far as risk is concerned, I'll give an opinion. IMO, the chips likely occur when the gears are still turning while they are being engaged. It could be from something else, but once engaged, they don't normally chip like that. I would be willing to put up with the vibration, if not excessive, until a convenient time to split the tractor presented itself. Just take it easy on 1st gear, and make sure you don't have one where it is impossible to go into first without a little grind, due to a faulty pilot bushing or clutch adjustment. The risk is that further chips, or breakage of that gear, could take out several other gears before you get the transmission stopped.
Others may not agree with this, and may even have different experiences.
'52 Cub ("Great Personality") 148xxx
'48 Cub with FH ("Gunny Cub") 38xxx
'57 Lambretta (a slow work in progress)
'74 Triumph TR6 (Mama's toy)
In addition to what you have already done, get an inspection mirror so you can see in the valleys between the teeth and also look at the gear driving that gear. You are checking to see if there is a small piece of metal wedged between the teeth. It will be hard to see, may just look like a slightly shallower groove. I have never experienced your problem myself, but personally I would not expect that small a chip to cause as much of a vibration problem as you have described. also the mirror will make it possible to see the back side of the teeth.
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government lest it come to dominate our lives and interests." Patrick Henry
I agree with John. Something else is going on. Reverse idler bearings perhaps but it doesn't seem to have a vibration in reverse. Maybe the idler is quieted when torque is applied in reverse and rattles/vibrates while in first?? Just a SWAG. Another thought is the first gear (being taller) is picking up trash from the bottom of the case, causing the chips and vibrations. The chip I see in the picture doesn't look bad enough to cause vibrations by itself, IMHO.
Update: I jacked up the rear (blocked the front) and rotated the wheels in 1st so the 39-tooth gear would rotate. I used a mechanics mirror to look at the teeth at both sides. All clear except for the previously mentioned chips. I used a dental pick to scrape at each tooth "valley" and felt it catch on a few occasions. Perhaps some debris...not sure. But with a few flicks I couldn't get the pick to catch anymore. Flushed the fluid and put in new fluid. I put the shift cover back on, dropped her down, fired her up and took a spin around the yard. The vibration appears to be less than it was. Or maybe it's just wishful thinking. But I think everyone is right that I probably won't do any damage with old Betty as she is. If it gets really bad I'll park it and do a tear down.
On another note, I adjusted the clutch fingers by tightening the set screw in the center of each bolt 1/2 turn clockwise hoping I could reduce the flywheel speed faster as I'm pretty sure the pucks weren't making contact at all before. No difference. But I can say that the clutch pedal was all messed up so I had to realign it after doing the adjustments. I'll do 1/4 turns this weekend to see if it makes any difference. I've only had the tractor for two weeks but I know the grinding-into-gear noise well so I always let the flywheel stop before moving into gear. Might have to replace the pucks but I'm probably going to wait for Cecil's to have the pros give me their thoughts.
I feel progress was made and I couldn't have gotten this far without you guys. So, thank you.
PS-New tires on the back! Nice and smooooooth ride now!
She thinks my tractor's sexy...
The first/Reverse slider gear will most likely have bad teeth on it too
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8th Va fest link viewtopic.php?f=8&t=81392&p=657790#p657790
There is a specific adjustment for the clutch - the finger height should be 1 1/4.
Here is a link to the clutch adjustment procedure and specifications http://farmallcub.com/phpBB2/viewtopic.php?t=6994
Eddie - a 1959 International Lo-Boy named after my father in law, who who bought her new.
If you go transmission diving, put in the 1-R slider gear new as well. It's really your problem, not the driven gear. 13 tooth gear loses all battles of strength with 39 tooth gears.
You will get that kind of gear wear in cubs that have been worked hard in low gear.
Just pulled down a M5R2 transmission from an F150 that pushes snow in the winter and pulls trailer in the summer - 2 adjacent broken teeth on the Rev input gear and one really close to failure idler. Idler in fully reversed bending at about 40 teeth outlived the 15 tooth input gear. Previous builder didn't know what impending gear failure looked like.
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