Product Description
**Milwaukee parts change not only by model# but also by serial number. To look up your tools parts break down on Milwaukee's website please click here:
Milwaukee Oil Seal
Model Number: 43-44-5380
The Milwaukee 43-44-5380 Oil Seal is a genuine OEM replacement service part designed for the Milwaukee 5375-20 1/2 in. Hammer Drill (Serial C50A, July 2011 start date), Milwaukee's corded 120V 1/2 in. corded hammer drill built for concrete anchoring, masonry drilling, tile drilling, and general purpose drilling on wood, metal, and plastic. Identified as Figure 5 on Milwaukee service bulletin 54-24-6100, the oil seal is the elastomer sealing ring that mounts around the spindle shaft at the gearcase interface, providing the critical seal that retains the grease and lubricants inside the gearcase while excluding dust, concrete debris, drywall dust, and other jobsite contamination from the rotating ratchet mechanism and gear train. On a hammer drill specifically, the oil seal serves a dual protective function: first, it retains the specialized grease that lubricates the rotating and fixed ratchets that generate the hammer action, ensuring smooth ratchet engagement and long-term wear resistance; second, it excludes the highly abrasive concrete and masonry dust generated during hammer drilling from entering the mechanism, where dust contamination would cause premature wear of the ratchets, bearings, and gears.
A worn, cracked, hardened, or deformed oil seal is one of the most common failure modes on a heavy-use corded hammer drill, since the seal is exposed to continuous rotation, temperature cycling, and years of contamination pressure across the tool's service life. Symptoms of a failing oil seal include visible grease leaking from the gearcase, dust or debris ingress visible in the mechanism area, reduced hammer action performance due to grease loss from the ratchet mechanism, or accelerated wear of the internal components. Replacing the oil seal with this OEM service part restores correct sealing at the gearcase-spindle interface and prevents secondary damage from grease loss or contamination ingress. The 43-44-5380 is typically replaced as part of a broader gearcase service that may also include inspection or replacement of the companion Milwaukee 34-80-5380 Retaining Ring (Fig 4), 02-04-5380 Ball Bearing (Fig 6), 44-84-5375 Rotating Ratchet (Fig 7), 44-84-5376 Fixed Ratchet (Fig 8), and 38-50-5375 Spindle Shaft (Fig 9), all documented on the same bulletin 54-24-6100 and all sold separately. Because Milwaukee Tool specifies replacement parts by both catalog number and serial number, always verify your tool's serial number against the official Milwaukee 5375-20 service parts diagram before ordering. Verify by serial number using Milwaukee's online parts lookup before ordering to confirm correct fitment.
Features
- Genuine Milwaukee OEM replacement service part, direct factory part for the 43-44-5380 reference
- Elastomer oil seal for the Milwaukee 5375-20 1/2 in. Hammer Drill (Serial C50A)
- Documented as Figure 5 on Milwaukee service bulletin 54-24-6100 (July 2011 revised)
- Retains specialized grease inside the gearcase for correct ratchet mechanism lubrication
- Excludes concrete dust, masonry debris, and jobsite contamination from the mechanism
- Critical for smooth hammer action ratchet engagement and long-term wear resistance
- Prevents accelerated wear of ratchets, bearings, and gears from dust contamination
- Prevents grease loss that would compromise the hammer action performance
- Restores correct gearcase-to-spindle sealing at the elastomer interface
- Sized specifically to the 5375-20 hammer drill spindle shaft geometry
- Milwaukee specifies one oil seal per tool at the documented service position
- Manufactured to Milwaukee factory tolerances and material specifications
- Direct-fit replacement, no modification required for installation
Specifications
- Manufacturer: Milwaukee Tool
- Part Number: 43-44-5380
- Official Description: Oil Seal
- Component Type: Elastomer Gearcase Oil Seal
- Primary Fitment: Milwaukee 5375-20 1/2 in. Hammer Drill (Serial C50A, July 2011 start date)
- Service Bulletin Reference: 54-24-6100 (Revised), Figure 5
- Function: Retains gearcase grease and excludes dust/debris at the spindle shaft interface
- Tool Category: Milwaukee Corded 120V AC 1/2 in. Hammer Drill
- Required Quantity Per Tool: 1 oil seal per documented service position
- Companion Service Parts on Same Bulletin: Milwaukee 34-80-5380 Retaining Ring, 02-04-5380 Ball Bearing, 44-84-5375 Rotating Ratchet, 44-84-5376 Fixed Ratchet, 38-50-5375 Spindle Shaft (all sold separately)
- Quantity: Sold individually, 1 oil seal per order
- Part Type: OEM Service Replacement Part
Includes
- (1) Milwaukee 43-44-5380 Oil Seal
- NOT Included: Gearcase grease/lubricant. Milwaukee specifies a lightweight oil to saturate related felt seals during service. Refer to your tool's service manual for the correct grease specification, sold separately
- NOT Included: Companion service parts (retaining ring, ball bearing, rotating and fixed ratchets, spindle shaft, gearcase assembly). These vary by tool revision and should be inspected during oil seal service. Refer to your specific tool's service parts diagram for the correct part numbers, all sold separately
- Note: This oil seal is specific to the Milwaukee 5375-20 1/2 in. Hammer Drill (Serial C50A) documented on bulletin 54-24-6100. Milwaukee uses different oil seal part numbers across their broader tool catalog for different tool platforms, gearcase geometries, and spindle shaft sizes - these are NOT interchangeable with the 43-44-5380
- Note: Verify your tool's catalog number (5375-20) and serial number against the official Milwaukee parts diagram before ordering
