Belt Drive Systems
Belt Tensioner Assembly for Cummins 6C, ISB, QSB Engines – Direct Replacement
<p>Stop unexpected belt slippage and premature accessory failure on your Cummins-powered equipment — this <strong>belt tensioner</strong> delivers consistent, OEM-matched tension right out of the box. Built to replace 3936213, 5259022, and 3976831, it eliminates the guesswork and downtime caused by worn or inconsistent factory units.</p> <ul> <li>Fits Cummins 6C, ISB, QSB, 4B3.9, 6B5.9, B6.7, and 10+ other engine families — no cross-referencing headaches</li> <li>Features a precision-calibrated hydraulic damper (not just spring-loaded) for smooth, vibration-dampened tension control</li> <li>Ready to ship same day from our Guangzhou warehouse — no waiting weeks for OEM backorders</li> <li>Backed by XUNPO’s 6-month warranty and technical verification support before you order</li> </ul>
Lead Time
2-5 Days
Warranty
3-12 Months
Min. Order
1 Piece
Ships To
120+ Countries
Request a Quote
Response within 24 hours
Product Details
Product Specifications
| Parameter | Details |
|---|---|
| Part Name | Belt Tensioner Assembly |
| Part Number (OEM Reference) | 3936213, 5259022, 3976831 |
| Brand Compatibility | Cummins |
| Engine Model Fitment | 6C, ISB, QSB, 4B3.9, B4.5, 6B5.9, B6.7, 4B, 6B, ISC, QSC, ISL, QSL |
| Condition | New Aftermarket |
| Warranty | 3–12 months against manufacturing defects |
| Packaging | Individual protective packaging with foam cushioning and reinforced export carton |
Compatible Models
| Brand | Applicable Models |
|---|---|
| Cummins | 6C, ISB, QSB, 4B3.9, B4.5, 6B5.9, B6.7, 4B, 6B, ISC, QSC, ISL, QSL |
Tired of Belt Slippage and Engine Overheating? Get the Right Belt Tensioner Assembly for Your Cummins 6C, ISB, and QSB Engines
Every unplanned engine shutdown costs fleet operators thousands in lost productivity and repair labor. Counterfeit or worn-out belt tensioners cause inconsistent drive belt tension — leading to slippage, squealing, overheating, and eventual alternator or water pump failure. OEM parts often take 3–4 weeks to arrive, while low-cost alternatives fail within months under real-world load.
OEM-Equivalent Quality, Ready to Ship from Guangzhou Warehouse
This belt tensioner assembly is manufactured in ISO-certified facilities and subjected to pre-shipment performance testing for consistent spring force, pivot smoothness, and mounting bolt torque retention. Designed for daily use in excavators, gensets, and construction equipment powered by Cummins 6C, ISB, and QSB engines, it delivers reliable tension control during high-load cycles — just like original equipment. With 10 years’ experience supplying heavy equipment parts globally, XUNPO ensures every unit meets OEM dimensional and functional specs.
Where This Part Works
This belt tensioner operates under continuous thermal cycling and vibration in demanding environments: quarry haul trucks, port container handlers, municipal waste compactors, and rental fleet excavators. It maintains precise belt tension across temperature ranges from –20°C to +110°C, preventing loss of auxiliary power to critical systems like cooling fans and air compressors. A failed tensioner on a Cummins QSB engine in a marine genset can trigger automatic shutdown — making correct part selection mission-critical. Replacement belt tensioner for Cummins 4B3.9 and 6B5.9 engines must match OEM pivot geometry and spring rate.
Engineering Details That Matter
The housing is precision die-cast aluminum alloy (A380), offering optimal strength-to-weight ratio and thermal stability — critical for maintaining alignment as engine bay temperatures fluctuate. Internal pivot shafts are hardened to 58–62 HRC and ground to ±0.01 mm tolerance, ensuring zero play and extended service life under repeated shock loading. The automatic hydraulic damping mechanism uses ISO VG 46 mineral oil sealed in a double-lip nitrile rubber seal (NBR), rated to 150 psi and resistant to diesel fuel and coolant ingress. Mounting bolt holes conform exactly to Cummins SAE J1922 flange patterns, enabling direct interchange without adapters or modifications.
The Real Cost of Wrong Parts
A $35 counterfeit tensioner may save upfront but often fails within 200 operating hours — causing belt derailment, snapped serpentine belts, and collateral damage to alternators or AC compressors. Repair labor alone averages $180/hour; downtime for a mining loader exceeds $2,500/hour. Genuine aftermarket parts built to ISO 9001 and validated against Cummins engineering standards reduce total cost of ownership (TCO) by extending mean time between failures (MTBF) to 5,000+ hours. Belt tensioner for Cummins ISB engine must maintain ±3% tension deviation across full RPM range — only certified units guarantee this. Choosing based on price alone risks violating OEM maintenance schedules and voiding extended warranties.
Why Customers Trust XUNPO
• We source exclusively from ISO 9001-certified factories and perform incoming material inspection on every batch.
• Every belt tensioner assembly undergoes 100% functional testing: spring force verification (±2 N·m), pivot rotation torque (≤0.8 N·m), and dynamic vibration resistance at 3,500 rpm.
• All units carry 3–12 month warranty covering manufacturing defects — no questions asked.
• 10 years of global export experience serving 120+ countries, including repeat orders from fleet operators in USA, Germany, Nigeria, and Australia.
• Our 20+ technical specialists verify part compatibility using OEM service manuals and real-time cross-reference databases — response within 2 hours.
• Guangzhou warehouse holds 10,000+ SKUs, including this belt tensioner assembly — ready for same-day dispatch on confirmed orders.
Packaging & Shipping
- Individually sealed in anti-static polybag, secured in custom-cut EPE foam, packed in double-walled corrugated export carton
- In-stock items ship within 2–5 working days after payment confirmation
- Flexible logistics: Express (DHL/FedEx/UPS), air freight, or sea freight — selected per customer requirement
- Real-time tracking number provided upon dispatch, with proactive delivery updates
- Minimum order quantity: 1 piece — supports urgent field repairs and small fleet maintenance
Get Your Cummins Belt Tensioner Now
Your excavator or generator isn’t generating revenue while idle. Confirm fitment in under 2 hours and receive a competitive quote within 24 hours — just send us your part number, engine model, and required quantity. First-time buyers can request a sample for physical verification before placing bulk orders. Stock is limited — act now to avoid project delays.
Frequently Asked Questions
Q: Is this an original Cummins part or a replacement?
A: This is an OEM-equivalent aftermarket belt tensioner assembly, produced in ISO 9001-certified factories to meet Cummins dimensional, material, and performance specifications.
Q: How do I confirm if this fits my machine?
A: Send us your engine model (e.g., Cummins QSB 5.9), serial number prefix, and application — our technical team will verify compatibility within 2 hours.
Q: What is the warranty period?
A: 3–12 months against manufacturing defects. If failure occurs due to material or workmanship, we replace free of charge.
Q: What is the minimum order quantity?
A: 1 piece — no exceptions. Ideal for emergency replacements and small repair shops.
Q: How fast can you ship?
A: In-stock items ship within 2–5 working days. Express options available for urgent needs.
Q: Can I get a sample before ordering in bulk?
A: Yes — first-time customers may request one sample unit for evaluation and fitment testing.
Ready to order or need a quote?
Send your part number, machine model, and quantity — we’ll respond within 24 hours.
WhatsApp: +86 13316055942 | Email: talos@xunpojx.com
Compatible Brands
Our parts are engineered to meet or exceed OEM specifications. Please provide your machine model number and serial number when inquiring to confirm exact compatibility.
How to Confirm Compatibility
-
1
Find Your Machine Model
Locate the model plate on your machine, typically near the cab or engine compartment.
-
2
Note the Part Number
Check your parts manual or existing part for the OEM part number.
-
3
Contact Our Team
Our technical team verifies compatibility within 2 hours. Send us the details via the inquiry form or WhatsApp.
Shipping Information
Express Shipping
DHL, FedEx, UPS -- 3-7 business days worldwide
Sea Freight
Cost-effective option for bulk orders -- 15-35 days
Real-Time Tracking
Tracking number provided after shipment. 24/7 support available.
Warranty Policy
All parts come with manufacturer warranty. Duration varies by product category.
- Manufacturing defects covered in full
- Free replacement or full refund for defective parts
- Post-delivery technical support included
- Sample testing available for first-time buyers
ISO Certified Quality
All parts sourced from ISO-certified factories with strict QC processes and material traceability.
Competitive Pricing
Save 30-50% vs OEM prices without compromising quality. Transparent pricing with no hidden fees.
Fast 2-5 Day Shipping
Large Guangzhou warehouse with 10,000+ SKUs in stock. Most orders ship within 2-5 business days.
10+ Years Experience
20+ professionals with deep technical knowledge serving 1,000+ clients across 120+ countries.
24/7 Technical Support
Dedicated support team available around the clock. Part verification within 2 hours of inquiry.
Global Reach
Flexible shipping solutions including express and sea freight to 120+ countries with real-time tracking.
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Need a Custom Quote?
Our technical team responds within 24 hours. MOQ 1 piece. Ships to 120+ countries from our Guangzhou warehouse.