Easy
15-30 minutes
This is an OEM replacement part for use with Toro lawnmowers. The special drive spacer sits on top of the blade driver assembly, to allow space between the drive shaft. This spacer is sold individually, please see model diagram for additional parts.
Spacer-driver 106-3999
OEM part for: Toro, Lawn Boy
Part Number: 106-3999
$3.99
In Stock
Ships within 1 business day 
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Compatibility
This Spacer-driver will fit the following 752 machines. Confirm this part works with your model, and view the detailed model diagrams and repair help we have to offer.
Toro
20339 (407820000-999999999) 20339, 22in Recycler Lawn Mower With Smartstow, (Sn 407820000-999999999)
20340 (400000000-401499999) 20340, 22in Recycler Lawn Mower With Smartstow, (Sn 400000000-401499999)
20355 (405600000-405999999) 20355, 22in Recycler Lawn Mower With Smartstow, (Sn 405600000-405999999)
20961 (400000000-402099999) 20961, 55cm Recycler Lawn Mower With Smartstow, (Sn 400000000-402099999)
21765 (400000000-999999999) 21765, 55cm Recycler Lawn Mower With Smartstow, (Sn 400000000-999999999)
21768 (400000000-999999999) 21768, 55cm Recycler Lawn Mower With Smartstow, (Sn 400000000-999999999)
21774 (400000000-999999999) 21774, 55cm Recycler Lawn Mower With Smartstow, (Sn 400000000-999999999)
Lawn Boy
Show More Compatible ModelsThis item works with the following types of products:
- Lawn Mower Parts
This part replaces obsolete part #: 105-3999
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Just like the other parts I ordered together everything fit together was easy to order for a complete rebuild of the mower.
Parts showed up in good condition. Delivery was fast. The biggest thing for me was ordering. Was great to have the Dwg. With all the other parts that was needed to complete the job.
Guest -
October 25, 2022
Verified Purchase
The Right Fit
First thing great shipping the web site was excellent easy to use it made my search for the part easy an the part that I ordered was the perfect fit an it doesn’t get any better than that.
Guest -
April 8, 2020
Verified Purchase
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Customer Repair Instructions ?
All our customer repair instructions are solicited directly from other customers just like you who have purchased and replaced this exact part.
Blade drive assembly
Jeff - October 12, 2021
👍 2 of 2 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Medium
Time
15-30 minutes
Tools Used
Socket set, 32oz hammer
Ruptured drive assembly after running over a well hidden tree stump. Quarter size hole where the keyway used to be. Had to beat the thing with a 32oz
hammer like a mad because of short stroke clearance. ( yes I tried prying with 2x4 and crowbar, dont own a puller big enough). Upon removal I inspected and cleaned the shaft then lubricated it with greaseless spray, inserted the spacer into new drive and aligned the key way and it pushed on about an inch before it stopped cold, placed 2x4 on drive and hit it with aforementioned 32oz hammer like it owed me money, and drive slid right on. Hooked belt and installed blade in the usual way and righted the mower. Let the mower sit for a couple of hours to allow oil to settle, checked oil and gas then cut the grass. BTW pull the plug wire whenever I work on blade end stuff and use cardboard to catch any fluid when turned on side. All in all a $42 repair job on an 8 year old mower beats $400 for a new one.
hammer like a mad because of short stroke clearance. ( yes I tried prying with 2x4 and crowbar, dont own a puller big enough). Upon removal I inspected and cleaned the shaft then lubricated it with greaseless spray, inserted the spacer into new drive and aligned the key way and it pushed on about an inch before it stopped cold, placed 2x4 on drive and hit it with aforementioned 32oz hammer like it owed me money, and drive slid right on. Hooked belt and installed blade in the usual way and righted the mower. Let the mower sit for a couple of hours to allow oil to settle, checked oil and gas then cut the grass. BTW pull the plug wire whenever I work on blade end stuff and use cardboard to catch any fluid when turned on side. All in all a $42 repair job on an 8 year old mower beats $400 for a new one.
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Blade driver became loose because of a loose bolt and damaged the blade driver assembly and blade bolt.
Johnny - July 17, 2018
👍 1 of 1 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
Screwdriver, Wrench Set
The new parts were installed (slipped on) very easily. The lawn mower now works and I just mowed the front and back yards.
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Blade driver asm broke. Went to sharpen lawn mower and realized spacer-driver was broke and blade driver assembly was broke.
Dennis - May 2, 2018
👍 1 of 1 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
Socket set
1. Put new parts on with the blade that I had sharpened. Changed oil. Every thing went fine.
Parts diagram for replacement parts was a great help.
Parts diagram for replacement parts was a great help.
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Accelerator blade broken, needed to replace
Steven - July 1, 2017
👍 1 of 1 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Easy
Time
15-30 minutes
Tools Used
Screwdriver, Power Drill, Socket set, Rubber mallet
Parts Used
1. Turned on side with oil cap/stick off, dumped oil in container.
2. Took plug wire off plug
3. Used large screwdriver as blade stop, and 1/2 in ratchet with I believe 5/8 socket, tapped with mallet to loosen.
4. R n R, including oil.
2. Took plug wire off plug
3. Used large screwdriver as blade stop, and 1/2 in ratchet with I believe 5/8 socket, tapped with mallet to loosen.
4. R n R, including oil.
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Our customer service team are at the ready daily to answer your part and product questions. We have a dedicated staff with decades of collective experience in helping customers just like you purchase parts to repair their products.
All our part reviews are solicited directly from other customers who have purchased this exact part. While we moderate these reviews for profanity, offensive language or personally identifiable information, these reviews are posted exactly as submitted and no alterations are made by our team.
All our customer repair instructions are solicited directly from other customers just like you who have purchased and replaced this exact part. While we moderate these reviews for profanity, offensive language or personally identifiable information, these reviews are posted exactly as submitted and no alterations are made by our team.
Based on data from past customer purchasing behaviors, these parts are most commonly purchased together along with the part you are viewing. These parts may be necessary or helpful to replace to complete your current repair.
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