Belt Tensioner Assembly 3936213, Complete Unit for Cummins Engines — replacement for 6C, ISB, QSB, 6B5.9, B6.7, ISC, QSC, ISL, and QSL series. Guangzhou warehouse holds stock for same-day dispatch; one piece minimum covers your emergency repair without forcing a bulk buy. Send a photo of the worn nameplate and our team confirms fitment within hours.
Arrival timeline quoted at order confirmation based on your chosen freight method.
Single-Piece Dispatch — One belt tensioner assembly leaves our Guangzhou stock the same day the machine model is confirmed.
| Parameter | Value |
|---|---|
| Part Number | 3936213 |
| Product Type | Belt Tensioner |
| Cross-Reference | 3936213 (for identification purposes), 5259022 (cross-reference only), 3976831 (cross-reference only) |
| Machine Fitment | Cummins 6C, ISB, QSB, 4B3.9, B4.5, 6B5.9, B6.7, 4B, 6B, ISC, QSC, ISL, QSL; JOHN DEERE compatible equipment |
| Part Name | Belt Tensioner Assembly |
| Condition | New Aftermarket |
| Assembly State | Complete assembly |
| Warranty | 3–12 month warranty against manufacturing defects |
| Minimum Order | 1 piece |
| Quality Standard | ISO 9001 |
| Failure Symptom | Replacement Urgency |
|---|---|
| Squealing or chirping noise from front of engine at startup | Immediate — belt slip accelerates wear on all driven accessories |
| Visible wobble or lateral run-out on tensioner pulley | High — pulley bearing failure can throw the belt within operating hours |
| Cracked or broken tensioner arm spring housing | Critical — loss of tension causes belt detachment and coolant pump stop |
| Belt tracking off-center across pulley grooves | High — misalignment damages belt ribs and adjacent component bearings |
| Repeated belt breakage despite new belt installation | Immediate — underlying tensioner fault will destroy the replacement belt |
A belt tensioner assembly in stock fast shipping from Guangzhou reaches most international destinations within days, not weeks.
When an excavator or wheel loader sits idle on a job site because the belt threw, every hour of downtime compounds into missed deadlines and idle crew costs [NEED_CITE: typical hourly cost of unplanned construction equipment downtime]. Waiting for a supplier who insists on a minimum batch order or who needs several days just to confirm whether the part number still crosses to a current production number only extends that pain. We have seen site supervisors send blurry nameplate photos at odd hours because the original plate is painted over or corroded, and a wrong variant ordered in haste means the machine stays down for another shipping cycle. Getting the correct Belt Tensioner Assembly identified, pulled from shelf, and handed to a courier on the same working day is the difference between a brief interruption and a project delay.
This Belt Tensioner Assembly sits on our Guangzhou warehouse shelf as a complete, ready-to-install unit. When you send us a part number, a machine model, or even a photograph of a worn nameplate, our dispatch team cross-checks the identifier against the superseded and alternate reference numbers — 5259022 and 3976831 — to make sure the variant matches your specific engine build. Confirmation typically lands in your inbox within hours, not days. A belt tensioner assembly in stock fast shipping is only useful if the part number actually fits, so we verify before we pack.
Once the unit is boxed, the clock is in the hands of the freight network. Express courier services cover most Asia-Pacific destinations within a short window, while air freight serves longer-haul routes to the Middle East, Africa, and the Americas with predictable transit schedules. We quote the estimated arrival window at the time of order so you can plan crew and machine scheduling around a known date [NEED_CITE: international express freight transit variables for heavy equipment parts]. Packaging is built for single-piece courier handling — the tensioner assembly is cushioned and boxed to survive sorting hubs without cosmetic or functional damage. Weekend and holiday dispatch gaps are flagged upfront so there are no surprises.
The assembly state being complete means the pulley, arm, spring, and mounting hardware arrive as one unit — no sourcing separate bearings or springs from a second supplier. The tensioner spring force is calibrated to maintain correct belt deflection across the RPM range of Cummins 4B3.9 through QSL engines; too little force allows slip under load, while excessive force overloads accessory bearings. Pulley alignment and groove profile must match the belt rib geometry specified for your engine series, and this unit is built to that dimensional standard. Operating temperature tolerance covers the under-hood thermal environment of construction and mining equipment where ambient dust and radiant heat from exhaust components are constant factors. The ISO 9001 manufacturing standard means dimensional consistency across production batches, which matters when you are swapping a failed unit on a machine that cannot afford a trial fit.
Sending back a tensioner that does not fit means a second round of freight, a second wait, and a machine that has now been down for double the original estimate. Worse, a tensioner that bolts on but carries the wrong spring rate or pulley offset will cause the belt to track poorly, leading to premature belt failure and potential damage to the water pump and alternator bearings [NEED_CITE: belt drive misalignment effects on accessory bearing service life]. The repair bill then expands from a single tensioner swap into a multi-component job. This is why we insist on confirming the exact engine variant before releasing the part, even when the buyer is in a hurry.
Our Guangzhou warehouse keeps common belt drive components on the shelf, so a single belt tensioner assembly in stock fast shipping is not a promise — it is the default workflow. The minimum order is one piece, which matters when a contractor needs exactly one unit for an emergency repair and has no use for a bulk pack. Part identification works from a part number, a machine model, or a photograph, removing the bottleneck of unreadable nameplates. The same warranty terms apply whether the unit comes from our own production line or a qualified manufacturing partner, keeping accountability under one account. Cross-reference verification covers the superseded numbers 5259022 and 3976831, so older engine builds are not left without supply.
Send us the part number stamped on your old tensioner, the engine serial plate, or a clear photograph of the nameplate and pulley. We will cross-check against reference numbers and your specific engine series — whether it is a 4B3.9, a 6B5.9, or a QSL — and confirm stock status along with an arrival estimate so you can plan the repair window with confidence.
Q: Is this belt tensioner assembly in stock and how fast can you ship? A: Yes, this assembly is stocked in our Guangzhou warehouse as a complete ready-to-install unit. Once you confirm the engine variant and we verify the part number match, dispatch typically happens the same working day. Express and air freight options are quoted with an estimated arrival window so you know when the part reaches your site or workshop.
Q: What is the minimum order quantity for an urgent single repair? A: The minimum order is one piece. We routinely ship single belt tensioner assemblies for emergency breakdowns without requiring a bulk commitment. This applies whether the unit is going to a remote mine site or a metropolitan repair workshop, and the same warranty terms cover every individual piece.
Q: How quickly can the part arrive at my location? A: Arrival depends on your destination and chosen freight method. Express courier covers most regional routes within a short transit window, while air freight serves intercontinental destinations on scheduled services. We provide an estimated delivery date at the time of order so you can coordinate machine repair scheduling around a known arrival.
Q: My engine nameplate is worn and the number is unreadable — how do I confirm fitment? A: Send us a photograph of whatever remains on the nameplate, the engine serial number if visible, or the machine model. Our team cross-references the image against the compatible Cummins and JOHN DEERE engine range, including superseded numbers, and confirms whether 3936213 or an alternate reference matches your specific build before we ship.
Q: What happens if the part does not match when it arrives? A: If a fitment discrepancy is found upon arrival, contact us with photographs of the received unit and your engine plate. We will verify the mismatch, arrange a resolution, and dispatch the correct variant. Our pre-shipment confirmation process is designed to prevent this, but we stand behind every unit under the stated warranty terms.
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