The OEM Oil Seal 3.750x5.685x1.250 SYN NBR is designed for rotary shaft applications around a 3.750-inch shaft with a nominal 5.685-inch maximum outside diameter and an overall axial section of approximately 1.250 inches.

The supplied image shows a substantial metallic outer assembly with a stepped or flanged profile and a dark inner sealing section. This indicates that the product should not be treated as a simple standard radial oil seal based only on ID × OD × Width.

The SYN designation is manufacturer-specific. The exact:

• Sealing-lip geometry
• Number of sealing lips or elements
• Lip orientation
• Dust-exclusion arrangement
• Metal carrier geometry
• Reinforcement structure
• Spring configuration
• Axial shoulder or flange dimensions
• Installation direction

should be verified against the original seal, OEM drawing, or equipment cross-section before selecting a replacement.

The user-specified sealing material is NBR (Nitrile Butadiene Rubber), which is generally suitable for:

• Mineral oils
• Gear oils
• Hydraulic oils
• Bearing grease
• Petroleum-based lubricants
• General industrial lubricating fluids

NBR generally provides good resistance to petroleum-based oil, grease, abrasion, and mechanical wear in normal industrial applications. Compatibility should be verified before use with aggressive chemicals, certain fuels, specialized synthetic lubricants, ozone-rich environments, or sustained high-temperature service.

The inch dimensions convert approximately to:

Shaft diameter: 3.750 inches / 95.25 mm

Maximum outside diameter: 5.685 inches / approximately 144.40 mm

Axial width: 1.250 inches / 31.75 mm

The relatively deep 31.75 mm axial section and visible stepped metal geometry make complete dimensional verification especially important before installation.

⚙️ Applications

• Heavy industrial gearboxes
• Large bearing housings
• Mechanical transmissions
• Axle and hub assemblies
• Industrial drive systems
• Construction machinery
• Agricultural machinery
• Conveyor drive assemblies
• Legacy rotating machinery
• OEM equipment overhaul

🎯 Benefits

✔ Suitable for 3.750-inch shaft applications

✔ Deep 1.250-inch axial construction

✔ NBR suitable for many oil and grease applications

✔ Strong metal-supported configuration

✔ Stepped / flanged outer structure visible in supplied product

✔ Suitable for heavy industrial rotating equipment

✔ Useful for maintenance of specialized legacy machinery

✔ Appropriate for repair and overhaul applications

✔ Replacement candidate when complete SYN geometry matches

🧠 Technical Insight

• OEM SYN Seal Reference
• Deep-Section Rotary Shaft Seal
• 1.250-Inch / 31.75 mm Axial Section
• NBR Sealing Material
• Stepped / Flanged Metal Carrier
• Manufacturer-Specific SYN Profile
• 95.25 mm Shaft Diameter
• Exact SYN Cross-Section Must Be Verified

✅ Key Features

• OEM Industrial Seal
• SYN Profile Reference
• Oil-Resistant NBR Material
• Metal-Supported Construction
• Deep Axial Section
• 3.750x5.685x1.250 Dimensions
• Heavy-Duty Replacement Application
• Cross-Reference Support Available

📊 Specifications

Brand: OEM

Model / Profile: SYN

Size: 3.750 × 5.685 × 1.250 inch

Metric Equivalent: Approximately 95.25 × 144.40 × 31.75 mm

Type: Deep-Section Industrial Rotary Shaft Seal

Material: NBR (Nitrile Butadiene Rubber), as specified

Profile: SYN

Construction: Manufacturer-Specific Metal-Supported Rotary Shaft-Seal Construction

Visible Construction in Supplied Photo: Large stepped/flanged metal outer carrier with dark inner sealing element

Lip Design: SYN profile; verify exact sealing-lip geometry, number of lips or sealing elements, and orientation against the original seal or technical drawing

Dust Lip: Verify from the actual SYN cross-section

Spring Type: Verify from the actual seal construction

Shaft Diameter (ID): 3.750 inches / 95.25 mm

Maximum Outside Diameter: 5.685 inches / approximately 144.40 mm

Width: 1.250 inches / 31.75 mm

Outer Profile: Stepped / flanged metal geometry visible; exact shoulder diameters and axial dimensions must be verified

Pressure Capability: Primarily low-pressure rotary shaft-sealing service unless the specific OEM design states otherwise

Lubrication: Compatible oil and grease

Temperature Range: Typically approximately -30°C to +100°C for standard NBR; verify actual compound, lubricant, speed, and operating conditions

Speed Consideration: Permissible speed depends on shaft diameter, shaft finish, lubrication, temperature, alignment, concentricity, runout, seal loading, and actual SYN construction

Installation Consideration: Verify the complete stepped/flanged profile, installation depth, housing shoulder geometry, shaft finish and hardness, axial positioning, concentricity, runout, and lip orientation

Application Class: Heavy-Duty Industrial Bearing, Gearbox, Transmission, Axle, and Legacy Rotating Equipment

Standard: Inch-Size Specialized OEM Seal

🔁 Equivalent

Suitable replacement or cross-reference candidate for compatible:

• OEM SYN NBR Rotary Shaft Seal
• OEM 3.750x5.685x1.250 Oil Seal
• 95.25x144.40x31.75 Shaft Seal
• 3.750-Inch Shaft Oil Seal
• Deep-Section NBR Oil Seal
• Flanged Rotary Shaft Seal
• Stepped Metal-Case Oil Seal
• Heavy-Duty Bearing Housing Seal
• Heavy Gearbox Shaft Seal
• Legacy Equipment SYN Seal

The same nominal ID, maximum OD, and width do not guarantee interchangeability. A replacement must also match the original SYN cross-section, sealing-lip geometry, number of sealing elements, stepped/flanged carrier geometry, reinforcement structure, spring configuration, axial dimensions, installation direction, material specification, and operating requirements.

(Always verify dimensions, SYN profile, complete outer profile, shaft finish, shaft hardness, housing geometry, installation depth, lubricant compatibility, rotational speed, temperature, concentricity, runout, pressure, and operating conditions before ordering.)

📦 Availability

✅ In Stock

🚚 Fast Delivery Available

🌎 Worldwide Shipping Available

📦 MOQ: 1 Piece

🏭 Suitable for heavy gearbox overhaul, large bearing-housing maintenance, transmission repair, axle assemblies, industrial drive systems, construction machinery, agricultural machinery, legacy-equipment restoration, and compatible OEM applications.

📲 Contact via LINE ID: dusitrea

📧 Email: sales@seal4go.com

💬 Technical support available before ordering

🔍 Assistance available for cross-reference and equivalent part identification