I have Craftsman 917.388740 self-propelled mower. The original drive belt stretched & no longer had enough tension, even with adjustments, to move the wheels. Unfortunately, Sears online & phone parts, as well as other online parts stores, no longer show the drive mechanism on their parts diagrams or list a belt (I triple checked model number), so I didn't know what size belt to get.

I took the old belt to a shop & they sold me new belt that's a little shorter which I installed & adjusted using the knob on the drive lever. Now it takes off at high speed with lever in off position.

  • I removed corrosion & polished the inner surface of drive pulley.
  • I took the lever mechanism apart to make sure cable travels the full amount & lubricated cable which slides easily.

Unfortunately, the problem persists.

Does anybody know correct belt size for this model or have other recommendations?

  • 2
    I’m voting to close this question because it's not a home improvement related question
    – Ack
    Jun 23, 2020 at 17:30
  • 1
    It sounds to me like you've still got too much tension on the belt. If you've adjusted the drive system to its maximum travel and the belt is still too tight, you may need a longer belt. It's also possible that, even though the cable is moving, the clutch that it's supposed to control is stuck, or that the cable came off the clutch mechanism while you were fiddling with other things.
    – FreeMan
    Jun 23, 2020 at 17:33
  • WTH? You don’t adjust the belt tension with the drive lever! The drive lever is telling the transmission which ratio to use. It’s going forward because it thinks you are commanding that, because you messed with the drive lever linkage. Unmess it. Then adjust drive belt tension in the place you do that, which is not anywhere near the transmission. Jun 23, 2020 at 17:34
  • The manual seems to indicate that the belt tension isn't adjustable. Can you clarify what you adjusted?
    – isherwood
    Jun 23, 2020 at 18:24
  • 1
    @harper Also, your tone seems a little harsh for a first answer. If I were being an idiot I would accept your dismissive tone. But in the future, perhaps you should allow that you might not always understand the problem exactly. But thank you for answering.
    – Joel
    Jun 24, 2020 at 20:54


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