This is the Holset 3786778HX, an HE351VE variable geometry turbocharger remanufactured by Holset (Cummins Turbo Technologies) for the Cummins ISB 6.7L in medium-duty trucks. It is a complete turbo with the electronic actuator fitted. It replaces Cummins 4955397, 4955398 and 4955543 (exchange numbers 4955397RX, 4955398RX and 4955543RX), Holset 5322099HX and turbo kit number 4352325. Holset assembly numbers that cross to it include 3771645, 3771646, 3771649, 3771658 and 3771659.

These turbos are replaced for a nozzle ring stuck with soot, a failed actuator, low boost, turbo speed or actuator fault codes, oil in the intake and shaft play. Because this one comes with the actuator already on it, it covers a turbo failure and an actuator failure in one part. The new twin is 3786778H. Two catalogs list this same number as an HE300VG, so order by the part number on your old turbo and not by the model name.

Specifications

Fits / Applications

• Cummins ISB 6.7L in medium-duty (midrange) trucks
• Replaces Cummins 4955397RX, 4955398RX and 4955543RX
• Complete turbo with actuator
• Ram pickups take other Holset numbers. Check the engine serial number.

The actuator comes fitted to the turbo. Do not use the actuator arm or housing as a handle when you lift it. Fit new gaskets, check the oil feed and drain for restriction, and clear the cause of the old failure (soot, oil supply, a foreign object) before you start the engine.

Part Numbers & Cross Reference

Holset 3786778HX  ·  Holset, new version 3786778H  ·  Holset remanufactured 5322099HX  ·  Cummins ReCon 4955397RX  ·  Cummins ReCon 4955398RX  ·  Cummins ReCon 4955543RX  ·  Cummins 4955397  ·  Cummins 4955398  ·  Cummins 4955543  ·  Cummins / Holset 5322099  ·  Cummins / Holset 5325892  ·  Cummins / Holset 5325908  ·  Cummins / Holset 5325909  ·  Turbo kit 4352325  ·  Holset assembly 3771645  ·  Holset assembly 3771646  ·  Holset assembly 3771649  ·  Holset assembly 3771658  ·  Holset assembly 3771659

Cross-reference numbers can change with engine serial, build year and emissions tier, so treat this list as a starting point. Send us your engine serial number and we will confirm the exact match against your build before anything ships. That check is free and takes a few minutes.

Frequently Asked Questions

Will the 3786778HX fit a Ram 2500 or 3500 pickup?

It is not catalogued for Ram pickups. This is a Cummins ISB 6.7L turbo for medium-duty trucks, and Ram pickups take other Holset numbers. Call 530-668-0818 with your VIN or engine serial number and we will match it.

What numbers does the 3786778HX replace?

Cummins 4955397RX, 4955398RX and 4955543RX, Holset 5322099HX and turbo kit number 4352325. Holset assembly numbers 3771645, 3771646, 3771649, 3771658 and 3771659 cross to it as well. The new version of the same turbo is 3786778H.

Does it come with the actuator?

Yes. It is a complete HE351VE turbo with the electronic actuator fitted.

Is it new or remanufactured, and is there a core?

It is remanufactured by Holset, the turbo division of Cummins. A refundable core applies, and it comes back when we receive your old turbo.

Related Parts

• Cummins ISB 6.7L Midrange HE300VG Turbocharger with Actuator | Holset 3786222HX Remanufactured
• Cummins ISB 6.7L HE351VE Turbocharger with Actuator | Holset 3786775HX Remanufactured (Cummins 4955399)
• Cummins ISB 6.7L HE300VG Turbocharger without Actuator | Alliant Power AP90045 Remanufactured
• Komatsu SAA6D107E, SAA4D107E & Cummins QSB6.7 CP3 Fuel Pump | Bosch 0445020109 New (Cummins 4989266)

Why Buy From Valley Fuel Injection

We are a diesel fuel-injection and turbocharger shop in Woodland, CA, rebuilding pumps, injectors and turbos on our own benches since 1993, not a drop-ship storefront. When you call, you talk to the people who test these units. We verify fitment against your engine serial, VIN or build date before anything ships, so the right part arrives the first time.