How do I confirm pilotpart420819-8514678915320 fits my machine?

Compare the OEM or reference part number, machine model, engine model, and serial number. You can also submit a fitment inquiry before ordering.

In Stock

Belt Tensioner 3978021 3976833 for Cummins Engine 4BT 4BTA 6CT

For Cummins Belt Tensioner

Belt Tensioner 3978021 for Cummins

Q: What part numbers are associated with this Belt Tensioner?

3978021, 4BTA, 4B3.9, 6B5.9, 3976833

OEM / REF: 3978021SKU: pilotpart420819-8514678915320

Belt Tensioner 3978021 3976833 for Cummins Engine 4BT 4BTA 6CT is a Belt Tensioner replacement part for Cummins Seals, Filters & Maintenance Parts, categorized under Seals, Filters & Maintenance Parts > Belt Tensioner. Use OEM part number 3978021 and confirm machine model, engine model, and serial details before che...

Stock: In stock
Condition: New
Fitment: Cummins Engine Spare Parts
Category: Belt Tensioner

Fitment support before you order
Worldwide delivery options

In stock — ready to order

$86.50USD/EA

Estimated delivery by quantity

Estimated delivery windows
Qty	Estimated delivery
1	Oct 22 – Oct 29
10	Oct 20 – Oct 27
50	Oct 18 – Oct 25

Estimates from today; confirm exact lead time before payment.

Quantity

Confirm fitment before ordering →

Lead times can vary by freight route and customs. Contact support for expedited shipping.

Belt Tensioner Description

This Belt Tensioner is indexed for Cummins s: Fit for Engine: Cummins 4BT, 4BTA, 6CT, 4B3.9, 6B5.9, B4.5 CM2350 B146C, B5.9 G, B5.9 GAS PLUS CM556, B5.9 LPG PLUS CM556, ISB CM850, ISC8.3 CM2250, QSB4.5 CM2250 EC, QSB4.5 CM2350 B106, QSB4.5 CM850(CM2850), QSB5.9 30 CM550, QSB5.9 CM850, QSB6.7 CM850(CM2850), QSK95 CM2350 K143C, QSL9 CM850(CM2850). Compare reference number 3978021 against the label on your existing Cummins component before ordering.

Additional cross references on file: 4BTA, 4B3.9, 6B5.9. If your machine plate shows a different number, submit a fitment inquiry with photos before checkout.

Part Numbers and Cross References

39780214BTA4B3.96B5.93976833

Applications

Cummins s: Fit for Engine: Cummins 4BT, 4BTA, 6CT, 4B3.9, 6B5.9, B4.5 CM2350 B146C, B5.9 G, B5.9 GAS PLUS CM556, B5.9 LPG PLUS CM556, ISB CM850, ISC8.3 CM2250, QSB4.5 CM2250 EC, QSB4.5 CM2350 B106, QSB4.5 CM850(CM2850), QSB5.9 30 CM550, QSB5.9 CM850, QSB6.7 CM850(CM2850), QSK95 CM2350 K143C, QSL9 CM850(CM2850)

Fitment Notes

Brand or application signal: Cummins Engine Spare Parts
Product family: Belt Tensioner
System category: Engine Spare Parts > Belt Drive Systems > Belt Tensioner
Recommended verification: OEM number, engine model, serial number, old part photos, and dimensions.

Shipping & Returns

Availability: InStock
Shipping: Shipping quotes can be confirmed before payment for heavy or urgent orders.
Returns: Returns are easier when fitment is confirmed before ordering.
B2B support: Bulk, fleet, and repair-shop requests can be handled through the inquiry form.

Frequently Asked Questions

How do I confirm this part fits my machine?

Match the OEM or reference number first, then verify machine model, engine model, serial number, connector layout, mounting points, and old part photos.

Can I order if my part number is not listed?

Yes. Send the old part number, machine plate, and photos through the fitment inquiry form. Support can review possible replacements or alternatives.

Is this an OEM part?

Products are indexed as replacement parts unless explicitly marked otherwise. Always compare reference numbers and confirm fitment before purchase.