Lawnboy Self Propel Chatters on engagement

Discussion in 'Mechanic and Repair' started by 4Running, Feb 2, 2010.

  1. 4Running

    4Running LawnSite Member
    from Tx
    Posts: 32


    I have a Lawnboy 10323 and a 10525. Both units chatter a bit upon engagement of the self propel. For example, if I squeeze the bail slightly to maneuver around an obstacle it chatters, that the bail vibrates. Both of the belts are new, and are maybe a bit stiff? The drive pully seems to be round, and the input drive shaft doesn't seem bent. Once it is fully engaged the unit runs smooth.

    BTW both of these units are like a Toro in that they operate by the transmission moving to tighten and loosen the belt.

    Any Ideas?

  2. stihlboy

    stihlboy LawnSite Member
    Posts: 44

    are the belts properly tensioned?

    also a stiff belt has this effect untill they are worn in
    best of luck to you
  3. 4Running

    4Running LawnSite Member
    from Tx
    Posts: 32

    The belt tightens when you squeeze the bail to engage the self propel. Maybe I could try tightening the cable?
  4. topsites

    topsites LawnSite Fanatic
    Posts: 21,653

    I'm not sure if tightening is going to fix it, as in you might have to loosen OR tighten it
    but I think playing with the adjustments as you study the mechanism is worth a shot.
  5. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Posts: 2,231

    If you start the unit and engage the self propelled system with the drive wheels off the ground, do the drive wheels operate? If the drive wheels operate the proceed with the next test. With the drive belt cover off to observe and with the path of the mower blocked, place the drive wheels on the ground and engage the transmission. If the drive wheels fail to turn but the transmission pulley continues to turn and chatter, you have found the source of the problem.

    Lawn Boy/Toro transmissions experienced numerous problems with that transmission. What has occurred is that the input gear(#104-7668) and the bevel gear on the transmission shaft(#104-7669) have become worn enough that they do not properly engage, therefore chatter.

    Remove and disassemble the transmission. Remove and replace the input gear, the bevel gear and install new thrust washers(#36-4791). Worn thrust washers can contribute to the problem you're having. To remove the input gear, place a 3/4"(as I recall) deepwell socket on the portion of the input gear which is inside the transmission and remove the retaining nut on the transmission pulley. You can drive the pin out of the bevel gear which retains the bevel gear to the drive shaft to remove it.

    If the drive wheels do not turn in the first test, then you have problems with the clutch/friction washers and engagement dog although this normally does not lead to the chattering you describe.

    My guess the parts will run $30-50. If you are mechanically inclined it's a pretty simple fix. While you're at it, replace the clutch/friction washers, engagement dogs, and e-clips. Replace the pivot arms as well if they are loose on the shaft.

    My guess is that the cost of all the parts will be around $100. A complete transmission is around $140, as I recall, but you will still have the cost of the external parts.

    A shop repair will probably be in the $150-200 range which really isn't cost effective considering the cost of the mower.

  6. 4Running

    4Running LawnSite Member
    from Tx
    Posts: 32

    You know it passes both tests, but I still think something is up. And I think that bevel gear and pinion are at fault on both of my lawn-boys.

    Thats very good advice, I was confused by your part numbers at first, but they are the updated part numbers from what is on the Lawn-Boy parts viewer. I was just going to get the pinion gear, but now I will get the bevel gear and the thrust washers.
  7. 4Running

    4Running LawnSite Member
    from Tx
    Posts: 32

    Ok the 10525 3spd trans and the 10323 single speed trans use the same parts.

    Here they are

    36-4791 Thrust Washer $0.22 x2
    104-7669 Pinion Gear $7.20 x1
    104-7668 Bevel Gear $13.50x1

    Pretty cheap I think, Ill go ahead and order these.
  8. DT Lawn Care

    DT Lawn Care LawnSite Senior Member
    Posts: 850

    Sounds very similar to what my John Deere 14SE is doing. I just replace the plastic wheel sprockets every couple years and don't worry about it.
  9. dutch1

    dutch1 LawnSite Silver Member
    from Jayhawk
    Posts: 2,231

    Most often, in my experience. the problem you are experiencing is related to the input gear, bevel gear and worn thrust washer. I've made 60+ relacement of those parts over the last 12 years but DT's replay jogged my memory about of a similar problem that was a result of wear in the pivot arm/pivot arm recess that was allowing the pinion on the drive shaft end to ratchet against the gear on the wheel. Good luck.

  10. Valk

    Valk LawnSite Silver Member
    Posts: 2,711

    For Toro's 'Personal Pace style' transmission mowers:

    1) if only ONE wheel is spinning then starting with the side that doesn't spin, replace the wheelhub parts listed above (plastic thrust-washer thing-a-ma-bob, etc... :))...THEN do the OTHER side as well for your own peace of mind. A bad bevel gear acts the same way.

    2) if you're having issues with BOTH wheels not releasing when backing up, then the belt tension needs addressing...whether that's by adjusting the cable up near the handle/bail mechanism...or by an older type adjustment made at the back of the mower where the cables enter. Newer mowers do not have the latter I believe.

    3) I've read around here that these single speed Personal Pace tranny's are a bit of a weak link and may only have a life of 300hrs...give or take. I may very well be wrong, but a new one gets close to $200, just for the part(s).

    I'm unsure about the complexity of making actual repairs to the tranny innards it may be a lot easier to replace with a new on.

    Removing the entire transmission & axle assembly is a real pain...

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