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Buy transmission or repair old one.

6132 Views 15 Replies 7 Participants Last post by  RjMaan
I have a 1999 Toro SR-21S model 20043 (serial number 9911071). It's self propelled. Or was. Now it's just noisy -- sounds like the innards of the transmission box are shredding themselves. Now and then things catch and the mower moves forward a few feet, but mostly not.

I used it last fall with the transmission disabled because it's a great leaf mulcher and bagger. But it's clearly not designed for a human to push it around -- it's a lot of work.

I found a Toro parts list for this mower. I wanted a part number for the transmission (gear box), but it's shown as N/A. Lots of part numbers for the parts within and sticking out of the gear box. It seems I can't order an intact gear box from Toro.

Amazon and Ebay have gear boxes for sale, with part numbers, and if I work enough I can trace them back to Toro mowers, but not a 1999 model 20043.

I would buy an whole gear box if i could, and if I have to, I would buy the internal gear box parts and rebuild mine. What I'm trying to figure out: am I correct in thinking that there is no way to buy a gear box for this mower, and I actually have to buy quite a few parts and rebuild the one I have? Or can I just buy a gear box (even though it doesn't say it's for a 1999 model 20043) and install it?

Leaves are falling, and a complete gear box would be quickest, if I can just figure out which to buy. And any rebuild would be a lot faster if I knew what parts I needed. Some parts would be obvious, but might be some that are needed whether they look ok or not. I need help here :)
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Hello and welcome to MLF Dan. I believe I found your transmission number and there is a used one currently listed on ebay. Found trans number here-

Toro Part 104-7674, GEAR CASE ASM |

Used transmission here-

OEM Used Toro 104-7674 Gear Case Transmission SUPER RECYCLER Lawn mower | eBay
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Thanks for the reply.

I went to Toro Part 104-7674, GEAR CASE ASM |
(Parts Tree site for this part) -- it shows model numbers for mowers this part fits -- and it does have an entry for:

Toro 20043 (SR-21SB) - Toro SR-21SB Super Recycler Mower (SN: 210000001 - 210999999) (2001) - HOUSING, HANDLE BRACKETS, AND WHEEL ASSEMBLY

When I research the model 20043, it's always shown as:
2001 (serial numbers 210000001 - 210999999) [ ON THE LIST ]
2000 (serial numbers 200000001 - 200999999)
1999 (serial numbers 9900001 - 9999999). [ MY TORO ]

If the model 20043 was listed, without the year, I would be more comfortable thinking that all years of the 20043's would fit. As it is, it seems the 1999 isn't a fit.

Or am I over thinking this?

Edit: reviewing that list again, there are no mowers shown earlier than 2001. Makes me even more uncomfortable trying to fit it into a 1999.
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Repair clinic says part number 104-7618 fits, but Parts Tree does not agree.

Is it possible that all these parts would fit? I have no experience here.
New transmissions are well over $100, no matter what part number I use. I read somewhere that I can improve the ease of pushing the mower (when the transmission is broken) by opening the gear box and removing parts so the rear wheels spin freely all the time.

If that works, and the mower isn't so hard to push, I may just forget fixing the transmission. Or at least put it off for another year. I only use it for mulching leaves in the fall.
I have the 20043, my serial is 9909625. Bought it new April of 2000. :tango_face_smile:

Original part number I came up with just now is 99-1525
Toro crosses it to 104-7618

Item #16 on the housing, handle brackets and wheel assy. exploded view:

Shows available and in stock at, $157.88 through them. :Thumb up:
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We have a service manual for the different Toro drives in the reference library::Reading:

If you have the free time and will to mess with it, definately would be cheaper to pull it apart and just replace the gear or gears that are worn out.
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I have the time. The manual is awesome. I'll poke through it and see if I can't make sense of things. Got no excuse at this point. May as well replace the broken parts and let the mower push itself.

This is good :)
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I watched a youtube video where a guy took the trans out of a toro or maybe removed just the gears by the wheels to make the mower easier to push, been awhile since I saw that video....he claims it was almost like pushing a standard mower
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Opened up the transmission, and decided I needed just two parts -- the gear attached to the pulley, and the gear it meshes with. Toro part numbers 104-7668 (Toro price $17.34) and 104-7667 (Toro price $9.08). Items #10 and #15 on the Toro Gear Case Assembly breakout.

Getting the pulley off the transmission was a lot harder than the manual implies. Manual shows a ratchet on the nut, and one hand holding the pulley in place. In my case, the nut was really stuck, and I ended up opening the transmission and using a 22mm socket to hold the gear in place (and the pulley in place) to get the nut off. Awkward. A bench vise might have made things a lot easier.

Other than the pulley nut, manual was very clear, and things went quickly. Will be a while before parts arrive, unless local dealer has them.
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You've gotta love these older machines were everything is serviceable!
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Local Big R had one part, ordered in the other, and called me when it arrived. (I now like Big R -- never been there before.)

Blew $5 on #2 lithium grease -- old transmission grease out, new grease in. Total damages for this project now at $28 (parts) + $5 (grease) = $33.

Replacing parts in transmission was easy -- getting the transmission back in the mower was more complicated, but probably because I didn't read the manual for that part of it.

Ran a test, and mower works fine and all the grinding noises are gone. Wish I had some way to slow the mower down, though. It has just one speed and it's geared for someone in a hurry.

Thanks for all the help. I needed it.
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Good job and saved a bunch of money to boot! :ThumbUp:

Yeah, long as you push on the handle firmly it will try to run away. I always thought it would be easier to control especially for people not used to running a personal pace variable speed drive to have the top end speed designed slower on them too. If your mowing around something on a hill side it's pretty easy to spin the tires when going up hill.
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getting the transmission back in the mower was more complicated, but probably because I didn't read the manual for that part of it.
manuals are for reading after the job is finished so you can see where those extra parts you didnt need should have went lol
Bah! I always figure those extra parts I have leftover are just because I was more efficient at assembly then the factory was! :Thumb up:
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I think it depends on your budget. If you have a budget then you should purchase the new one or if older transmission works well in future after repair then you should repair it.
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