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Cummins 4939018 is the 28 volt alternator with a cooling fan and V belt pulley, a black rear cover with B+, D+ and E terminals and a single mounting foot. It is used on Cummins 6CT8.3 engines. This aftermarket version has the same mounting and electrical connector as the original, so it plugs in and bolts on where the old one came off.
The same part is also sold as Cummins 3979372 and JFZ2710.
Sold as one unit. Check the number on your old part, or in the parts manual for your machine, before ordering.
| Part Type | Alternator |
| Replaces | Cummins 4939018 |
| Engine | Cummins 6CT8.3, 6CT |
| Voltage | 28 V |
| Cross references | Cummins 3979372, JFZ2710 |
| Fits | Cummins 6CT8.3 and 6CT diesel engines |
| Condition | New, aftermarket |
| Stat. HS-Code | 851150 |
| Country of Manufacture | China |
Cummins machines
Check the part number on your old unit before ordering.
| Cummins Part No.(SPM Part No.) | Fits |
|---|---|
| 4939018(SPM-HEP-4750) | Cummins 6CT8.3 and 6CT diesel engines |
| 3979372(SPM-HEP-4750) | Cummins 6CT8.3 and 6CT diesel engines |
| JFZ2710(SPM-HEP-4750) | Cummins 6CT8.3 and 6CT diesel engines |
Battery not charging
A charge warning light or flat batteries every morning point to the alternator once the belt and wiring check out.
Noise
A worn bearing whines or grinds.
Low voltage at idle
Weak output shows as dim lights and slow electrics at idle.
Fit with a new belt
Change the belt and check the tensioner when fitting the alternator.
We check what other aftermarket sellers charge for this same part. Their prices on the date we checked:
| Seller | Price | Checked |
|---|---|---|
| FridayParts | USD 241.45 | 31 Oct 2026 |
| eBay, aftermarket seller | USD 279.99 | 31 Oct 2026 |
| SINOCMP | USD 299.00 | 31 Oct 2026 |
| Spare Part Mart | USD 204.99 | Today |
Our price of USD 204.99 is 15% to 31% less than these sellers.
Found this part cheaper somewhere else? Send us the listing and we will beat it by 5% under our Price Beat Guarantee. Every order is also covered by our 30 day money back guarantee.
Yes, it was made for the Cummins 6CT8.3, and 1 more listed under compatible equipment. Check the old alternator is marked 4939018 or one of the cross references, because makers change parts between serial ranges.
On the Cummins 6CT8.3, typically 5,000 to 10,000 hours, depending on how often the machine is started and how well the batteries are kept.
A charge warning, low battery voltage with the engine running, flickering lights or bearing noise.
Check the exciter or D+ wire, the sense wire and the belt tension. A missing excite feed is the most common reason a good alternator does not charge.
Battery voltage under load, the earth strap and the main cable. A weak supply makes a good alternator look faulty and will burn out the new one.
No. It is an aftermarket alternator made to replace the Cummins 4939018. It is not made by the original manufacturer; the number only shows what it replaces.
Live rates for the quantity selected, delivered to your door. Confirmed at checkout.
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