What 3006738 Actually Is
This is the rear main seal at the flywheel end of the crankshaft, supplied as a double-lip silicone seal for wet-clutch applications. Inner diameter is 6.00 in, outer diameter is 6.757 in. The double lip matters: wet-clutch engines see oil on both sides of the seal area, and a single-lip seal built for a dry clutch setup will weep once it is loaded.
The silicone elastomer is specified to hold up to heat and oil pressure at the rear of the block, which is where the seal lives its whole life. The sealing surface is sized to the original 855 and N14 rear bore, so the seal registers in the housing the same way the part it replaces did.
Application coverage listed is Cummins N14, NT855, NH855 and GTA855 wet-clutch diesel engines, the kind found in Class-8 trucks such as Kenworth W900 and T800 and Volvo VNL. Engine serial number is what settles it, not the truck badge on the hood.
Why These Numbers Cross
Cummins 212832, 3001772 and 3904353 all show up against this same rear crank seal position on the 855 family. Those numbers reflect running changes and packaging differences over a long production life rather than a different sealing geometry. When the bore size and lip configuration stay the same, the numbers supersede into one another and land on the part described here.
Komatsu 6711-21-1320 appears because Komatsu built and used 855-series Cummins engines under license. Same block, same rear bore, different number on the box. PAI 136023 is an aftermarket catalog number for the identical position. All of these are listed for identification only.
The practical cross-check is dimensional. If the number on your old seal or its packaging is on this list, and the measured bore and shaft diameters match 6.757 in outer and 6.00 in inner, you are almost certainly on the right part. Confirm by VIN or engine serial before you order.
Check Before You Order
Wet clutch or dry clutch is the first question. This seal is the double-lip wet-clutch version. Pull the inspection cover and look at how the flywheel housing is set up before you assume. Ordering the wrong lip configuration means the transmission comes back out.
Second, inspect the crankshaft sealing surface. A grooved crank flange will cut a new seal in short order, which is why a wear sleeve is part of this application. If the old sleeve is scored, replace it with the seal rather than dropping a fresh lip onto a worn ride surface.
3006738 Cross-Reference & Interchange Numbers
These manufacturer and aftermarket numbers commonly cross-reference to 3006738. 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 |
|---|---|
| Cummins | 212832, 3001772, 3904353 |
| Komatsu | 6711-21-1320 |
| PAI | 136023 |
Frequently asked questions
Is 3006738 the same seal as 3904353?
Those numbers cross to the same rear crankshaft seal position on the Cummins 855 family. Number changes over the production run generally reflect packaging and supersession rather than a different sealing geometry. Verify by measuring your bore and shaft and by checking your engine serial number before ordering.
How do I know if I have a wet clutch N14?
Pull the flywheel housing inspection cover and look at the clutch. Wet-clutch setups run oil at the flywheel end and require the double-lip seal described here. If your engine runs a dry clutch, this is not the correct seal for it. When in doubt, go off the engine serial number.
Do I need a new wear sleeve with the seal?
If the crank sealing surface is grooved or scored, yes. A new lip riding in an old groove will leak again quickly. Inspect the surface with the flywheel off and replace the sleeve at the same time as the seal if there is any visible wear track.
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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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