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Hi everyone, looking for any advice and trying to see if someone else is having this same problem. I have had my Troy Bilt Automatic Bronco for 3 years and the variable speed drive pulley has fallen off 4 times. Is this a common problem with this model or just for me? How can I repair this? Thanks for any advice or experience you can share.

Welcome to the forum.


http://service.mtdproducts.com/Training_Education/769_06667_700_series_riders.pdf page 51 servicing the variable speed idler.

Thanks very much but I really want to know if anyone else has had this issue. I can fix it but I don't think I should have this problem so often. The guy I'm in contact with at Loews has talked to MTD and they don't want to help fix it, But I think there's a problem with the machine because it started falling off after only 1 month of use. If no one else has this problem, mine must be a lemon.

Just replace the locknut!!!!

If you want help there, at least post the model numbers off of the tag under the seat!

Wm2014 said:

Hi everyone, looking for any advice and trying to see if someone else is having this same problem. I have had my Troy Bilt Automatic Bronco for 3 years and the variable speed drive pulley has fallen off 4 times. Is this a common problem with this model or just for me? How can I repair this? Thanks for any advice or experience you can share.

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Yes this keeps happening to me as well. I bought my troy bilt back in 2016. It first happened to me about a month ago. Pulley fell off and I could see the threading was bad so I ordered an entirely new pulley. I replaced it and it happened again. The third time I fixed it I put some lock tight on the retention bolt. Got a solid 20 minutes of mowing done and it came off completely. I noticed that the pulley seemed really hot. hotter then it should be. The bolt and washer were extremely hot as well. I checked the bearings and everything seems fine there. Was wondering if you ever found out the cause.

I also have a 2016 Bronco Troy Bilt automatic transmission riding mower and had to replace the variable speed pulley three times.

Falls off is not much of a description for people to be able to offer useful suggestions as there are quite a few ways a pulley can "fall off" .
We also need a common base to work from so lets use this diagram ( if it is for your mower ) and the item numbers to keep things simple.
https://www.jackssmallengines.com/jacks-parts-lookup/manufacturer/troy-bilt/13-lawn-tractors/2016-models/13wv78ks011-bronco-2016/drive
If this is not your mower we need the model number should be 13??????? so we can find the right diagram.
I have about 4 bronco's in the repair run & have never had any fall off.

Did anyone ever get a good answer on why this is happening?
Model#: 13WV78KS011
Mine keeps coming off I put it back in put a bolt and a washer and it works for a bit then it falls right off. The pulley is hot and the bolt has made a large hole on the washer(guessing from being hot)and that’s why it slips off.Model#: 13WV78KS011

First both of the 6203-2RS bearings needs replacing. Second new screw (bolt) and washer need to be installed using blue Loctite. MTD used red Loctite but I prefer the blue version over the red as you migh need to take apart again later. MTD 710-05339A version is a captive washer type of the 5/16-24 X .75 Grd 5 screw. Torque to standard torque of 14 ft-lbs.