Medium
30-60 minutes
This is a complete, genuine replacement Makita gearbox. It is commonly found in newer Makita Lithium-Ion powered drills. The gearbox is a complete assembly, including the threaded spindle, selector collar, housings, and internal gears and bearings. The gearbox comes pre lubricated and sealed and is ready to install. This part is compatible with the Makita drills listed below, but it will not fit any other power tools.
Gear Assembly 125430-5
OEM part for: Makita
Part Number: 125430-5
$95.06
In Stock
Ships within 1 business day 
Product Description ?
- OEM Makita drill gearbox
- Complete gearbox assembly
- Ships ready for installation
- Classification: Part
- Weight: 1.65 lbs.
- Shipping: Ships Worldwide
Compatibility
This part will fit the following 2 machines
Makita
BHP451 Drill / Driver View Diagrams & Manuals
BHP451 (Type 2) Drill View Diagrams & Manuals
This item works with the following types of products:
- Drill Parts
This part replaces obsolete part #: 125317-1
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Never received it, lost in transit but receive top notch customer service
Never received the part (lost in transit) and was credited back the cost, seems like a great company and will probably buy from them again when needed, customer service was spot on, thanks again!
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June 3, 2019
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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.
Clutch would slip and not drill.
William - October 11, 2016
👍 7 of 7 people found this instruction helpful
Tool Type
Cordless Drill
Difficulty
Easy
Time
15-30 minutes
Tools Used
Screwdriver, Allen wrench,hammer
Parts Used
Remove the battery. Remove the LH thread chuck screw. Put the largest allen wrench in the chuck that will fit, (short end). Tighten chuck onto allen wrench. Make sure drill is in low gear and in the drill mode. Lay the drill down on your work table. Strike the long end of the allen wrench with a hammer to unscrew the chuck from the spindle (RH thread) and remove the chuck. Remove the screws from the housing and separate. Make note or take pictures where all of the parts are located. Remove the old gear assembly , and install the new one. Then assemble the drill in reverse order.
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the hammer drill transmission failed. It would no longer turn the chuck.
Bruce - August 28, 2021
Tool Type
Hammer Drill
Difficulty
Hard
Time
More than 2 hours
Tools Used
Screwdriver, vice grips, bench vice dremel grinder
Parts Used
1. disassembled the drill body by removing all of the side screws and the end cap screws (2) and the 4 screws that mount the transmission to the drill body
2. Lifted the motor and the transmission out of the body cases.
3. Separated the motor from the transmission
4. Removed the brush holder plate from the motor. I released the tension from one of the brushes to allow the motor to be easily separated from the brush holder plate.
5. Cleaned the motor with electrical component solvent spray. Motor commutator had quite a bit of dirt inside which limited the air flow through it
6. Reattached the motor to the transmission and installed the assembly in the case. This required an exceptional amount of patience and determination because it would not go back together as easily as it came apart.
7. Finally, reassembled the case/internals by returning all of the screws to their rightful locations.
8. All that remains to be done is to attach the chuck. It will not come free from the old transmission because the left-handed mounting screw is stuck. I am in the process of drilling/grinding the screw out. Have several hours into the chuck removal with no end in sight\
9. The part that I ordered from was in pieces when it arrived about ten days late. I was able to figure out how to return all of the little gears to their appointed locations and get the rear cover back on. FEDEX was the carrier and after some nudging, they produced the damaged package. I think the driver was embarrassed because he dropped the package and left hurriedly.
10. Now I am in the final approach, using a small grinder to remove the remainder of the screw that wasn't drilled away. A problem has occurred with holding the chuck carrier shaft while I attempt to smack the chuck loose from it. If it weren't for the stuck chuck, replacing the broken transmission would have been straight forward.
2. Lifted the motor and the transmission out of the body cases.
3. Separated the motor from the transmission
4. Removed the brush holder plate from the motor. I released the tension from one of the brushes to allow the motor to be easily separated from the brush holder plate.
5. Cleaned the motor with electrical component solvent spray. Motor commutator had quite a bit of dirt inside which limited the air flow through it
6. Reattached the motor to the transmission and installed the assembly in the case. This required an exceptional amount of patience and determination because it would not go back together as easily as it came apart.
7. Finally, reassembled the case/internals by returning all of the screws to their rightful locations.
8. All that remains to be done is to attach the chuck. It will not come free from the old transmission because the left-handed mounting screw is stuck. I am in the process of drilling/grinding the screw out. Have several hours into the chuck removal with no end in sight\
9. The part that I ordered from was in pieces when it arrived about ten days late. I was able to figure out how to return all of the little gears to their appointed locations and get the rear cover back on. FEDEX was the carrier and after some nudging, they produced the damaged package. I think the driver was embarrassed because he dropped the package and left hurriedly.
10. Now I am in the final approach, using a small grinder to remove the remainder of the screw that wasn't drilled away. A problem has occurred with holding the chuck carrier shaft while I attempt to smack the chuck loose from it. If it weren't for the stuck chuck, replacing the broken transmission would have been straight forward.
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checked on u - tube
Chuck - April 11, 2021
Tool Type
Cordless Drill
Difficulty
Medium
Time
Less than 15 minutes
Tools Used
Screwdriver, Wrench Set, vise
Parts Used
remove drill housing, then removed old gear assembly then install new.
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Makita hammer drill gearbox slipping, hammer function failed.
Thomas - April 18, 2020
Tool Type
Cordless Drill
Difficulty
Medium
Time
30-60 minutes
Tools Used
Screwdriver, Vise, acetylene torch, sledge hammer, hex keys
Parts Used
1. Removed four screws holding gearbox to drill.
2. Removed two screws and rear cover of drill motor housing.
3. Removed eight screws in housing and removed top side, leaving motor and gearbox in place.
4. Note position of motor. Motor must be in precise position to reinstall housing.
5. Tipped up and removed gearbox.
6. Installed new gearbox.
7. Carefully repositioned internal parts, and reinstalled and fastened top housing, rear cover, and fastened gearbox.
8. Removed chuck retaining screw in old gearbox, attempted to remove chuck. Failed.
9. Smashed old gearbox with sledgehammer to access chuck shaft.
10. Attempted chuck removal again with chuck shaft in large machine vise. Failed.
11. Heated chuck shaft with acetylene torch until nicely smoking. Clamped shaft in vise, and finally removed the chuck with moderate force using an impact driver. Whew.
12. Installed chuck on new gearbox, and installed retainer screw with Locktight.
The project was problem free and fast with the exception of the chuck removal. It is like having a brand new tool with the new gearbox.
2. Removed two screws and rear cover of drill motor housing.
3. Removed eight screws in housing and removed top side, leaving motor and gearbox in place.
4. Note position of motor. Motor must be in precise position to reinstall housing.
5. Tipped up and removed gearbox.
6. Installed new gearbox.
7. Carefully repositioned internal parts, and reinstalled and fastened top housing, rear cover, and fastened gearbox.
8. Removed chuck retaining screw in old gearbox, attempted to remove chuck. Failed.
9. Smashed old gearbox with sledgehammer to access chuck shaft.
10. Attempted chuck removal again with chuck shaft in large machine vise. Failed.
11. Heated chuck shaft with acetylene torch until nicely smoking. Clamped shaft in vise, and finally removed the chuck with moderate force using an impact driver. Whew.
12. Installed chuck on new gearbox, and installed retainer screw with Locktight.
The project was problem free and fast with the exception of the chuck removal. It is like having a brand new tool with the new gearbox.
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Gearbox gears stripped
Tim - March 12, 2018
Tool Type
Cordless Drill
Difficulty
Medium
Time
30-60 minutes
Tools Used
Screwdriver
Parts Used
Removed gear assembly, and replaced. hard to describe but had a little trouble seating motor in housing, got it though. I would recommend this for a fix it kinda person, not for someone not mechanical.
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The keyless chuck broke along with second gear breaking as well.
William - May 21, 2017
Tool Type
Hammer Drill
Difficulty
Easy
Time
Less than 15 minutes
Tools Used
Screwdriver
1. Removed the battery.
2. Opened the drill casing by removing all screws.
3. Removed the gear assembly and the chuck as one unit.
4. Replaced with the assembled gearbox and the chuck.
5. Secured the casing.
6. Attached the battery.
7. Tested, worked just fine.
2. Opened the drill casing by removing all screws.
3. Removed the gear assembly and the chuck as one unit.
4. Replaced with the assembled gearbox and the chuck.
5. Secured the casing.
6. Attached the battery.
7. Tested, worked just fine.
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Gear unit had stripped.
Michael - September 3, 2017
👍 0 of 1 people found this instruction helpful
Tool Type
Cordless Drill
Difficulty
Medium
Time
30-60 minutes
Tools Used
Screwdriver
Parts Used
I pretty much followed the simple instructions on your web site. There was one nuance though. When you have removed all of the screws that hold the drill together, and you GENTLY pry it in half, you need to pay close attention to the orientation of the motor. It only goes back in one way. Mine had a red line on it that I think was supposed to point to the right side (as when you are holding it by the handle normally) of the drill. The two halves won't go together if this motor orientation isn't correct.
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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.
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