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Lawn Boy walk-behind lost 3rd gear

Posted by steve71 Philly area (My Page) on
Sun, Feb 20, 11 at 9:02

My 1993 walk-behind started slipping/chattering in 3rd gear recently. All the transmission gears look perfect and I changed the grease, but the problem is still there. The handle vibrates and it feels like the gears are trying to mesh. The belt is fine and so are 1st and 2nd. Has anyone experienced this problem? The shifter cable does not appear to be adjustable, else I would try to lengthen it a tad. I am thinking that the transmission lever may not be moving far enough for 3rd gear to engage. The only clutch seems to be in the drive wheels, so all gears would be affected, right?

Follow-Up Postings:

RE: Lawn Boy walk-behind lost 3rd gear

I would assume that the shift keys or inside of the gears are worn. You could try unhooking the cable to see if a nudge over on the lever helps. When you go inside again, verify that the input bearings are healthy yet. What's the model #?

RE: Lawn Boy walk-behind lost 3rd gear

@tomplum Thanks for the pro tips! Disconnecting the cable and nudging the shift lever did not help, so the shift keys are looking more like the culprit, but now that you mention bearings, those could be making the sound that goes with this problem- a rapid, irregular metallic groaning noise that you can feel through the handle- not at all like gears grinding, more like a bad bearing. Went over every tooth in the gearbox and they all looked fine, so I will post again after further disassembly. This is a 10520 Gold Series, 21".

RE: Lawn Boy walk-behind lost 3rd gear

The weather finally warmed up today so I spent some time with the Lawn Boy. Opened the gearbox to examine the shift keys and bearings. Wow! There has to be a trick for removing the keys, and I hope it doesn't entail complete disassembly of a drive wheel! Does anyone know how to remove the keys and/or remove the drive shaft gears? I cleaned the sliding tracks and even though everything looks good, I think I should remove the keys and check the matching key holes in each gear. Thanks!

RE: Lawn Boy walk-behind lost 3rd gear

Mystery Solved. Take a look at this picture of the worn bushing alongside a new one. This goes in the side of the gearbox and the output shaft/axle spins in it. It is mainly lubricated by a felt washer on the axle, also, a tight drive cable will accelerate wear to this part. This little nugget costs $17, but it did it's job well for 22 seasons, sacrificing itself to save wear on the output shaft. When it got to have 1/8 inch play, the gears had trouble staying in contact.

Here is a link that might be useful: Worn bushing and new bushing.

RE: Lawn Boy walk-behind lost 3rd gear

Excellent job!

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