Toro Lawn Mower Transmission Replacement, Mower Repair #121-9178

This video provides step-by-step instructions for replacing the transmission on Toro lawn mowers. The most common reason for replacing the transmission is when the lawn mower wheels don’t turn.

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Additional lawn mower repair, troubleshooting tips, help with finding your model number, and part replacement videos:

All of the information in this transmission replacement video is applicable for the following brands: Toro.

Tools needed: socket wrench, snap ring pliers, wrench

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27 thoughts on “Toro Lawn Mower Transmission Replacement, Mower Repair #121-9178

  1. I replaced my transmission and everything seemed to go back together fine but now the mower just wont start. It was running fine when I replaced the transmission. Mine is a toro 6.5 hp model 20076. could dirty gas have gotten in carb when mower was on its side? Im' not even getting a spark it seems. plug is gapped to .030 and smells like gas. plz advise and what i should try. I thoulght i had this fixed and now it just wont start.

  2. Bad gas will not cause the no spark condition. You might have got a little extra oil in the cylinder and fouled out the spark plug. I would try a new spark plug, and if you still get no spark check the flywheel grounding arm. If it is touching the flywheel even when you pull the control lever back it will ground out the spark.

  3. Our 2004 (model 20017) mower has lost the self-propel and has a grinding noise when the bar is pushed down (personal pace). We replaced the belt and adjusted the cable and still have the problem. Would this be a transmission problem? I noticed one of your replies about the back wheels locking up when being pulled backwards and that has been a problem we've had the past few years as well. P.S. I wish our mower was as easy to disassemble as in your videos! Ours isn't designed as well. :

  4. I'm having the same issues as Stacy on my 2010 model 20332 mower. Wheels bind up backing up, and grinding noise when engaging transmission. I have changed out the tension spring on the handle, the transmission, both rear wheels, drive belt and drive pulley. When adjusting the cable, if I take out all the slack as directed, the wheels spin even without pushing the handle. So I have left a small bit of slack. The only thing I haven't changed out are the two brass gears at the ends of the trans shift. They appear to be ok, since they only contact the plastic gears on the inside of the wheels. Any ideas on why this is still happening?

  5. Can we just pull out the transmission and not replace it with a new one? Would this make the mower a push mower and still function OK otherwise?

  6. Fabulous Video, Followed the steps here and replaced my bad TORO transmission easily. Started @ 2:00 pm, completed the project then mowed my entire lawn and it is now only 5:00 pm. Thank you.

  7. I have a Troy Built 6.75 hp mower with the left  front Splined wheel locked up. How does that wheel turn with spline on the wheel shaft that will not turn/Can  anyone help me out here?
    The splined part looks to be pressed on the shaft.

  8. I replaced the transmission, adjusted the cable, and put a new belt on. But, the lawnmower doesn't move as fast as it use to. I can push it faster then the self propelled. Got any idea why?

  9. What parts do I likely need to replace if only one of my wheels occasionally locks up when pulling backward? The mower works fine moving forward. The gears on my rear wheels look OK and seem to turn fine when raised off the ground. With weight on them they seem to want to lock up. I have a 2010 model 20332. Thanks.

  10. I have a toro model 20074 with rear wheel drive and I noticed that only the right wheel will spin when engaged.should both wheels engage?

  11. These Hank Hill level vids are dumb cuz how many brand new mowers need replacement parts..try the same tricks on old rusted together machines that really need repair and see how simple and easy THAT is and see if you stay as clean as the guy in this vid.

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