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Discussion Starter · #1 ·
After a few years of use, my Bronco - 13YX78kS011 - has gone from being my reliable mower to the one that is always being worked on. This time, the mower has issues going forward when the accelerator is pushed down. It tries to go forward, and sometimes goes a little bit, but most of the time I hear a clanking noise from below the seat/battery and almost no forward movement. Reverse seems to work better, and I rarely have an issue in that gear.

Some troubleshooting I performed was verifying that all belts and pulleys move properly when the accelerator is pressed. I also verified that I can stop the rear wheels with my hands with the mower on jack stands and the accelerator pressed. It isn't taking much force to replicate the issue.

I'm pretty sure that I eliminated the belts and pulleys as the culprits, and I have been focusing on the transmission. I took it apart, and looked for the notorious worn dog gear, but sadly everything looked great inside. The only part in the transmission that I could not take apart was the differential assembly, as it is held together with rivets or something. It looks like there are planetary gears inside the enclosed portion, and I am wondering if these could be worn and causing the clanking noise I hear when I try to go forward.

Any additional insight is appreciated.
 

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Discussion Starter · #2 ·
I found this thread from a good bit ago:

I was hoping that my issue was as simple as inspecting and replacing the bushings, but everything measured fine on my transaxle.

I did look into the differential assembly a bit more, and found that the axles have some horizontal play. I'm not sure if that is standard, but it seems to be about 1/32" to 1/16" of play. My current hypothesis is that this play is not letting the planetary gears in the middle of the differential to engage properly, causing the slipping with a low amount of force.
 

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Discussion Starter · #4 ·
I'm having the same issue with my bronco. Did you find a solution?
Not yet. I'm pretty confident it is that part that needs to be replaced, but I don't want to bite the bullet on a new one yet. I am keeping an eye on FB and CL for a deal on a parts machine, or even going to local scrapyards and see what I can find.
 

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Not yet. I'm pretty confident it is that part that needs to be replaced, but I don't want to bite the bullet on a new one yet. I am keeping an eye on FB and CL for a deal on a parts machine, or even going to local scrapyards and see what I can find.

Keep us updated please.
 

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Discussion Starter · #6 · (Edited)
The culprit ended up being the horizontal play I noticed earlier. I ended up buying a flat washer to use as a shim, and after assembling the mower for the umpteenth time, the clunking was gone, and forward and rear directions were strong and fast.

Just in time for mowing season.
 
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