MTD riding mower jerky drive

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Old 01-22-21, 08:00 AM
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MTD riding mower jerky drive

My MTD riding mower model #13AH660F352 while in gear and driving is constantly jerking. I changed both belts but that didn't change anything. It started to do it in the spring and continued to get worse throughout the summer. I'm thinking that it's something in the transmission but would like to get confirmation from you experts and also how to fix it.
Any help would be appreciated.
 
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Old 01-22-21, 08:29 AM
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Check the operation of bearing on any idler pullys with the belts off.
 
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Old 01-22-21, 08:41 AM
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Probably a long shot, but you might jack up the rear end and make sure the wheels are firmly attached to the axles and that neither has a broken key. A year or so ago a buddy asked me to look his relatively similar Cub that had come to a halt, and after the fact told me that it had been jerking for a while, but we jacked it up and pulled one of the rear wheels right off, hub and all.
 
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Old 01-22-21, 08:57 AM
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Excessive gear backlash? Excessive clearance between a shaft and its bearing? How old?
 
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Old 01-22-21, 10:17 AM
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Just guessing but it's about 20 years old.
 
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Old 01-22-21, 10:31 AM
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At 20 YO this sounds like a "normal wear-out failure" rather than caused by a factory defect.
It may be easier to find when it fails outright and from your description that won't be long.

Sounds like this is a repair/replace decision and the price of parts is sometimes such that you will be on the fence with this decision.
 
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Old 01-22-21, 10:53 AM
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I just tried jacking it up and checked the wheels and they both look good and are attached. I put it in gear to check if it was engaging and it is.
Have you ever tried taking the trans/gearbox apart? Can I get parts for it?
 
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Old 01-22-21, 10:59 AM
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All of the pulleys were good with no bearing problems when I changed the belts.
 
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Old 01-22-21, 01:38 PM
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You gear box my not have a differential. Check by jacking up rear wheels. If you can turn one wheel while holding the other, you have a differential. If not you have a solid axle. On a solid axle, the rear wheel on inside of a turn must rotate the same number of revolutions as the outside wheel, yet travel a shorter distance. The result is the inside wheel jerks to add the needed distance.
 
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Old 01-22-21, 05:15 PM
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With the engine off, can you move either back wheel back and forth through a small angle? This should give you a reading of total gear backlash all the way back to the engine output shaft.
 
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Old 01-22-21, 10:29 PM
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It probably makes a whirring or whining sound in the rear end too, right? This is a common failure for these transmissions.
 
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Old 01-23-21, 08:00 AM
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Unhappy

Sounds like replace or rebuild the tranny.
 
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Old 01-23-21, 01:18 PM
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I checked the rear wheels with it jacked up and in gear and they both won't turn so there must not be a differential. While in neutral I could turn the wheels independently. One wheel with turn about 4 inches while holding the other and vice versa. If I jack it up and put it in gear and run it the mower wheels run smooth with no jerking. When I put it on the ground that's when it will jerk. It doesn't matter if I'm turning or going straight it jerks. I didn't notice any whining while it was moving.
If the tranny is bad are they rebuildable? Can I get parts for it?
 
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Old 01-23-21, 01:36 PM
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I'd replace the unit as an assembly. I rebuilt some of those years back and for the cost, time involved, and case wear you will have, I don't think rebuilding them is a viable option anymore..We just replace them or junk the mower these days.
 
 

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