Cub Cadet 123 Vibration
 

Hello,

I just got my first Cub Cadet. It's a model 123 that is in pretty good shape for a working tractor. It has a 48" mowing deck and a 42" snow thrower for the winters. I have a question for the forum. I just recently got it running after cleaning the carburetor, replacing the air filter, installing a new starter/generator belt and adjusting the PTO clutch.

Just test driving it around the yard today I noticed a vibration that may or may not be normal. At about half throttle or better there is enough vibration to be felt quite noticeably through the seat and steering wheel. Also the hood eventually vibrates free from the rubber washers that secure it's aft edge. The amount of vibration increases with throttle and does not change when the PTO is engaged or disengaged.

It doesn't feel like it's going to shake apart but it is more than I have felt on newer garden tractors. I know the engine on the narrow frame tractors is hard mounted to the frame so perhaps it's normal. Thanks in advance for any advice.

Regards,
Mike

Welcome, Mike.

Some vibration is normal on the "Thumper" engines (single cylinder). If you have someone close by with a similar model, give their machine a quick test drive. I have a Quiet-Line model 800 with the rubber ISO mounts; not too much vibration until the mower kicks in.

The hard-mount styles do transmit more shakes to the frame, seat, etc. Check the motor mounts and be sure they are all snugged to spec. Most of the newer lawn/garden tractors are v-twins, and usually rubber-isolation mounted so those are normally smoother.

Again, welcome to Only Cub Cadets. Put on the coffee, pull up a chair and stay awhile.

I would make sure the engine mount bolts are tight and check the driveshaft/rag joints for any wobble.

Bill

I forgot to mention, ( however, Berwil did remember) that the driveshaft flexible couplers [A.K.A. 'Rag joints'] can be a cause of vibration....

Does it still shake with the clutch pressed down?

:bigthink: if not, the flexible couplers could be the issue.

Regards

Cubby Guy

Thanks for the advice. I will check the engine mounts to make sure they are snug and check the rag joint. Is there a torque spec for the mounting bolts or just make sure they are snug.

Regards,
Mike

Welcome to OCC!:beerchug:

Regarding the rag joint, on a hydrostatic does the driveshaft always turn even in neutral with the brake fully depressed?

Another issue I noticed is that the neutral return mechanism connected to the brake overshoots neutral a bit. With the brake locked down there is a slight grinding noise from the hydrostat when starting. If I release the brake enough to move the selector lever I can put it fully in neutral and there is no noise. I looked up the procedure in the service manual to adjust the linkage and it is on the to do list.

-Mike

Welcome to OCC! Enjoy your 123! :beerchug:

Yes, the driveshaft on a hydro is always spinning at the same speed as the engine, there is no disconnect or clutch.

The whine is a common problem when the neutral brake return is out of adjustment, sounds like your on the way to fixing that one. :beerchug:

Bill

Thanks for the help guys! Eventually I am going to to a tear down and restoration. Maybe in the fall when the grass stops growing.

-Mike

Yes, you should be able to adjust the location of neutral from the bracket on the transmission, it's not very hard to do.

My best guess regarding the vibration issue is, something in the drive shaft, it could be any of a number of things, as mentioned before, check the flex coupler, the drive hub that bolts to the engine and check the drive shaft to make sure it isn't bent.

I found the vibration problem. The driveshaft is either bent or off-center at the rag joint end. There is a driveline shop down the street from me that can probably straighten it. What is the best way to get the shaft out? Can it be done without splitting the tractor?

Thanks,
Mike

I have the same problem with my 123. What threw me off was that it just started after I rebuilt my 301 and put it back in. I thought that if the shaft lived for so long being in the motor one way and now it's 180 off, maybe that's doing it. But, I can see the shaft wobbling quite a bit so I must have tweaked it a little during r and r of the motor or something. Bums me out but good to see you found yours though. And yeah, unfortunately you're going to have to split it. Not a bad job to do, looks intimidating but just a few steps and it's done. Leave the rear tires on, disconnect a couple brake linkages and trans to frame bolts and roll it right out. Obviously use jack stands for safety

The rear drive shaft coupler is prolly worn.the driveshaft has a little tit on the end of it, it wears and so does the coupler.

Unbolt the engine, disconnect the pto rod and slide the engine forward. Probably have to unbolt the "tin" under the dash tower (the one the drive shaft goes through).

Be careful not to break your hydro fan when pulling the shaft.. They're not too terribly tough after being heat cycled for 40 years and are easy to break.

Also.. You may be better off to pull the rear out to pull the shaft since all of the linkage and stuff back there is usually worn, or out of adjustment, anyhow (and normally have hydro leaks-o-plenty). May as well kill a couple of birds with the same stone. Good chance for a nice frame wash too.

I found the problem. The flex coupler is oblong and had one hole ripped out. The tit on the end of the shaft was worn on one side from running offset for what looks like quite some time. The coupler has a matching wear spot. The driveshaft is straight though and the fan is not damaged. I am going to try a new flex disc and rotate the shaft so that the two worn spots don't line up anymore and see what that does. Splitting the tractor was pretty easy so if this doesn't work I will order a coupler and replace it too. I could probably have the tit on the shaft welded and ground to fill in the worn spot if I have to.

The tractor is back together and the vibration and driveline wobble is gone. I put in a new flex disc and used some JB weld to fill in the divot in the coupler and re form the tit at the end of the driveshaft where it was worn away. After it was cured I filed everything back to what it should have been pre-wear. I figured the JB fix would be worth a shot before I ordered a new coupler and driveshaft.

I make driveshafts
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post 9

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Jeff

Jeff I checked mine tonight and the coupler on the opposite side of the flex coupler is what is loose, roll pin hole is ovaled out bad and whole thing wobbles on input shaft of hydro. Do you make the other piece that I'm talking about? Same model as OP, 123.