Farmall Cub

Me again. Problem #178. Changed tranny fluid from the iced coffee goo to clean 80 weight. Did the same for the onyx-black schmutz in the final drives. Still experiencing unusual vibration through the tranny under, and through, the seat while in 1st gear, mid throttle through full, while under load. No grinding or anything. 2nd and 3rd gears are super smooth. Just straight cut gear "side effects?" Or perhaps it's this morning's caffeine that's giving me the shakes and not the actual tractor!

Does it do something similar in reverse? If not, I would suspect the 39 tooth 1st gear. Is so, then the 1st/reverse gear splines that slide on the main (drive)shaft are worn badly or the shaft itself. In any event (gears, bearings, shafts) sounds like a teardown is in order.

Smokeycub wrote:Does it do something similar in reverse? If not, I would suspect the 39 tooth 1st gear. Is so, then the 1st/reverse gear splines that slide on the main (drive)shaft are worn badly or the shaft itself. In any event (gears, bearings, shafts) sounds like a teardown is in order.

Reverse is different. I don't get the same vibration at all, but the low whine of the straight gears is prevalent in both 1st and reverse; though that seems common with these machines.

I'm going to have to see about getting Betty to a cubfest for evaluation here soon. It's not easy to describe noises and vibrations and grunts etc etc via text!

Am I doing harm by driving the tractor? If the splines get worn enough, will I break something which will then break something else costing me even more? Should I just avoid using 1st gear?

Probably won't hurt it any more than it already is. If the vibration is really bad I wouldn't put it off for long, I might even park it until I could check it out with a tear down. You could pull off the shifter cover and see if the 39 tooth first gear has a lot of rotational slop or unusual play on the input (drive) shaft.

Ooo there's a good idea. I didn't know I could do that. I like to visualize and tinker and was upset when I learned that Superman was only a single individual and I couldn't see through steel to figure out what was going on inside!

Smokeycub wrote:You could pull off the shifter cover and see if the 39 tooth first gear has a lot of rotational slop or unusual play on the input (drive) shaft.

That's also a good opportunity to drain and flush the transmission, if you haven't already done so. Refill with 3.5 PINTS of gear oil.

I did a full fluid change in the last week or so. All nice and fresh! But yes if I hadn't it would have been a perfect opportunity!

OK - so what do I look for with the shifter cover off? Nothing seems visually out of the ordinary...but what do I know?

So if I'm correct, while standing on the left side of the tractor looking under the shift level I believe the gears go 3rd, 2nd, 1st and reverse from left to right. Regardless, each gear can be moved approximately .5mm by hand. The spline itself also has the same movement. No heavy wear on the teeth. When rotating the hand crank and turning each gear I see no obvious damage. No foreign objects. No aliens chipping away at Betty's tranny with tiny fenazatron beams either (which I half expected). (Sorry, I couldn't help myself)

Is this movement normal?

On a separate note, I find the design of these tractors fascinating. I think of what was required of the manufacturer to make these things so robust. Here we are, 60 years later, and Betty still runs like a top. I can't help but imagine all of the Americans working in the American factories to build these from scratch...it's almost emotional. What can I say...I'm American and proud! Which is why i'm not telling ANYONE that I'm putting in Chinese LEDs! Shhhh.

while you have the cover off, block the clutch down and with it in 1st gear (left shifter centered, right one forward) jack up a rear wheel and spin it by hand. Listen for unusual noise and watch for movement.

Hmmm. Every rotation and only for a split second the regular "gear noise" changes. It's as if somewhere there is just the slightest oddity. I don't see anything visually however. Interesting enough I also feel this same oddity with vibration through the seat post. I'll just stay out of 1st until I see the boys at Cecil's in October. Something's obviously (in the words of my 6 year old niece) "kaflooey."

If anyone has any thoughts as to what to check specifically I'd be up for more exploration! Thanks Don and Smokey!

Question.

Connecticut Calvin wrote:Every rotation and only for a split second the regular "gear noise" changes.

Each rotation of the rear tractor tire?

Following John' guidance. Mark the elevated rear tire at the top. Slowly rotate the tire. Count the number of times the gear noise changes in one complete revolution. Then do the same thing with tractor out of gear.

Then, same procedure on the opposite tire. Report results.

As instructed I blocked the clutch in place and put the tractor in 1st with the left wheel off the ground. I removed the shifter plate and turned the left wheel in both directions. It's actually every gear rotation, not tire. I'll do the same with the other wheel and also in neutral. I can tell you that I don't hear the "oddity" in 2nd or 3rd whole doing the same thing as above.

Sounds suspiciously like one bad tooth; either chipped or some irregular wear pattern.....look them over carefully with a light, and look especially at the corners of the teeth.

Do you see any wear on the side of the gear teeth on any of the gears? Not in the teeth where you'd expect to see wear but on the side of the teeth.

Brilliant! Gentlemen I think you nailed it. The lower 39-tooth 1st gear that has been mentioned has not one but three chipped teeth that can only be seen in the right light. Counting the largest chip as tooth 1, there are also chips on teeth 16 and 27. Of course I can only see one side of each tooth from under the shift lever plate. I was able to get a shot of the largest chip:


I cannot identify any chips on any other gear. So, does this appear to be the cuplrit? If so, how risky is it to run the tractor with this "damage?"

PS-My tranny fluid must have mixed a bit with remnants of the old "iced coffee" fluid...I'll change it again in coming weeks and flush appropriately.