What 3803369 Actually Is
This is the lube oil pump assembly that mounts to the front of the NT855 / 855 block and feeds the main oil gallery. Cast iron and steel construction, gear-type design. It pulls from the pan through the suction tube and pushes oil to the filter head, then to mains, rods, cam bushings, and the turbo feed line. No pump pressure, no bearing film.
The aftermarket unit we list is a direct replacement built for heavy-duty on-highway duty cycles — Class-8 linehaul, high idle hours, hot ambient work. It is not a reconditioned core. Material spec is cast iron and steel, same as the gear-pump architecture the 855 platform has used across Big Cam variants.
Application is Cummins NT855 / 855 Big Cam diesel engines found in Class-8 trucks including Kenworth W900 and T800 and Volvo VNL chassis. That is a family-level statement, not a fitment promise. The 855 ran a long time with revisions, so your engine serial number is the only thing that settles it.
Why These Numbers Cross
3803369 supersedes and interchanges with 3027421, 3068460, 3609829, 3609833, and 3821579. These are all the same basic gear pump body and mounting pattern on the 855 platform. Differences across the group come down to supersession history, minor casting revisions, and which service kit the pump originally shipped in — not a different pump geometry or a different drive gear.
When a number supersedes, the older part is usually discontinued and the later number is what gets shipped against all of them. That is why a truck built with 3027421 on the build sheet will have 3803369 in the current parts lookup. All the numbers above are listed for identification only; we are not affiliated with or authorized by any OEM.
Practical use: pull the old pump, wire-brush the casting, and read what is actually stamped on it. If the number on the part is anywhere in that list, 3803369 is the right starting point. If the stamp is unreadable or shows something not listed here, verify by engine serial before you order.
How These Pumps Fail
Gear pumps on the 855 usually fail slow, not sudden. Gear-to-body clearance opens up from abrasive wear — coolant in the oil, extended drain intervals, or a collapsed filter letting debris circulate. You see it as hot idle pressure dropping first, then low pressure at road speed, then a bearing knock. Check gauge readings hot at idle and at rated RPM before condemning anything.
Before you blame the pump, rule out the cheap stuff: plugged suction screen, cracked or loose pickup tube letting the pump suck air, a stuck pressure regulator, worn main and rod bearings dumping volume, and a sender or gauge reading wrong. A mechanical gauge teed into the main gallery settles the argument in ten minutes.
Install with new gaskets, prime the pump with clean engine oil before buttoning up, and torque the mounting fasteners to the service manual value for your engine. Verify oil pressure hot after the install and recheck after the first service interval. If the old pump came apart, flush the system and change the filter again early.
3803369 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 3803369. Use them to identify the part — then confirm the exact fit by VIN or the number stamped on your old unit before you order. An interchange is a starting point, not a fitment guarantee.
| Brand / Line | Cross-Reference Numbers |
|---|---|
| Cross-Reference | 3027421, 3068460, 3609829, 3609833, 3821579 |
Frequently asked questions
Will 3803369 fit my NT855 if my old pump is stamped 3609833?
3609833 is in the interchange group with 3803369, so it is the right place to start. Confirm with your engine serial number or by matching the mounting pattern and drive gear on the old pump before you install. Cross-reference identifies the part family — it does not guarantee fit on your specific build.
Is this a new pump or a rebuilt unit?
It is a new aftermarket pump, not a reconditioned core, built in cast iron and steel as a direct replacement for the 855 gear-type lube pump. It ships without gaskets installed, so plan on new gaskets as part of the job and prime it with clean oil before startup.
Low oil pressure on my Big Cam — is it always the pump?
No. Worn main and rod bearings, a plugged suction screen, an air leak at the pickup tube, or a stuck pressure regulator all read the same on the dash gauge. Tee in a mechanical gauge at the main gallery and check pressure hot at idle and at rated RPM before pulling the front of the engine apart.
Not sure it fits? We check before you pay.
Run your VIN and we’ll match parts to your exact truck, or call the counter — a person who knows trucks verifies fitment by OEM number before the order ships. No wrong-box returns.
More cross-reference guides
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Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.