Medium
30-60 minutes
This is an authentic Toro replacement part that has been sourced from the original manufacturer to be used with walk-behind lawnmowers. The key is used to link the pinion gear and the transaxle. This item fits into the slot on the axle and the keyway in the gear to allow the two parts to rotate in unison. This key is used with the right wheel and is sold as an individual replacement part.
Key-rocking, Rh 139-6643
OEM part for: Toro
Part Number: 139-6643
$9.96
In Stock
Ships within 1 business day 
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Compatibility
This Key-rocking, Rh will fit the following 743 machines. Confirm this part works with your model, and view the detailed model diagrams and repair help we have to offer.
Displaying 20 of 743 matching models.
743 total model matches. Try the above search to narrow your results.
This is the official OEM part for the following brands:
- Lawn Boy
- Toro
This item works with the following types of products:
- Lawn Mower
This part replaces obsolete part #: 66-6040 (Not Illustrated), 614445
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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.
Lawn mower left drive wheel was not driving properly.
Patrick - August 16, 2017
👍 4 of 4 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Easy
Time
15-30 minutes
Tools Used
Screwdriver, Pliers, Socket set, Wrench Set
1. Removed the rear wheel assemblies.
2. Removed the drive mechanism retaining c-clip on both rear wheels.
3. Removed the drive mechanisms.
4. Replaced the parts listed above and completed the repair on both rear wheels.
Note: Washer-Clutch and Ring-friction are the most common wear problems but, I replaced most everything since the mower was 7-yr old and still running very good.
2. Removed the drive mechanism retaining c-clip on both rear wheels.
3. Removed the drive mechanisms.
4. Replaced the parts listed above and completed the repair on both rear wheels.
Note: Washer-Clutch and Ring-friction are the most common wear problems but, I replaced most everything since the mower was 7-yr old and still running very good.
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Rear drive wheel gear and pinion were engaging intermittently due to the wobbling of the wheels. Wobbling of the wheels was caused by excess wear to the wheel bushings.
Daniel - July 22, 2017
👍 1 of 1 people found this instruction helpful
Tool Type
Lawn Mower
Difficulty
Easy
Time
30-60 minutes
Tools Used
Screwdriver, Pliers, Socket set
Removed rear wheel shoulder bolt.
Removed the rear wheel.
Removed the plastic drive gear housing.
Removed pinion gear retaining clip.
Removed the pinion gear.
I replaced other parts on the ends of the wheel drive shaft, but it was not actually necessary.
Installed the new pinion gear.
Installed the pinion gear retaining clip.
Installed the plastic drive gear housing.
Greased the wheel gears, pinion gears, wheel bushings and shoulder bolts liberally.
Replaced the wheel.
Replaced the shoulder bolt.
Removed the rear wheel.
Removed the plastic drive gear housing.
Removed pinion gear retaining clip.
Removed the pinion gear.
I replaced other parts on the ends of the wheel drive shaft, but it was not actually necessary.
Installed the new pinion gear.
Installed the pinion gear retaining clip.
Installed the plastic drive gear housing.
Greased the wheel gears, pinion gears, wheel bushings and shoulder bolts liberally.
Replaced the wheel.
Replaced the shoulder bolt.
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Self repell not working
PETER - July 24, 2020
Tool Type
Lawn Mower
Difficulty
Easy
Time
30-60 minutes
Tools Used
Socket set, Adjustable Wrench
Replace the missing and broken parts, with the new parts. The mower running like new.
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Toro Personal Pace 15 years old self propel really weak
Robert - April 20, 2020
Tool Type
Lawn Mower
Difficulty
Medium
Time
1-2 hours
Tools Used
Screwdriver, Socket set
Replaced Transmission, drive belt and all the parts related to the self propel mechanism.
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The drive shaft key way was worn on one side and did not engage properly
Roderick - October 6, 2019
Tool Type
Lawn Mower
Difficulty
Medium
Time
1-2 hours
Tools Used
Pliers, Socket set, Wrench Set
Remove both rear wheels.
Remove belt drive cover.
Remove spring from belt drive.
Remove drive belt.
Remove gear drive cover
Remove shaft
Remove pins in shaft.
Remove gear on shaft.
Install in reverse order.
Remove belt drive cover.
Remove spring from belt drive.
Remove drive belt.
Remove gear drive cover
Remove shaft
Remove pins in shaft.
Remove gear on shaft.
Install in reverse order.
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No self propelled, another mower bad wheels, last mower many parts on engine repaired or replaced
Casey - December 13, 2016
Tool Type
Lawn Mower
Difficulty
Medium
Time
1-2 hours
Tools Used
Screwdriver, Power Drill, Socket set, Wrench Set
Just did, nothing was too complicated. Taking apart motor was harder to get to, than what it took to replace the gasket.
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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.
All our installation videos are created and produced in collaboration with our in-house repair technician, Mark Sodja, who has helped millions of eReplacementParts customers over the last 13 years repair their products. Mark has years of experience in selling and repairing both commercial and residential products with a specialty in gas-powered equipment.
This data is collected from customers who submitted a repair instruction after replacing this exact part. Customers can rate how easy the repair was to complete and how long it took. We aggregate this data to provide a repair rating that allows customers to quickly determine the difficulty and time needed to perform their own repair.
