Western Star replacement engines & transmissions
Western Star Truck Engines & Transmissions
Western Star trucks have been built with Detroit, Cummins and, in older trucks, Caterpillar engines. Send us your VIN and unit details and we search supplier sources for a matching used replacement.
Engine families
Engines to check
Transmission families
Transmissions to check
Factory options varied by model and year. Links are starting points, not a fitment guarantee — we confirm against your VIN and serial numbers.
01Engine families found in Western Stars
Newer Western Star trucks, including the 49X, 47X and 57X, are commonly built with Detroit engines like the DD13, DD15 and DD16. Many Western Stars, especially vocational and heavy-haul trucks, have also run Cummins engines such as the ISX and X15. Older models like the 4900 were also built with Caterpillar and Detroit Series 60 engines.
02Transmissions
Western Stars commonly run Eaton Fuller manual transmissions, including 13- and 18-speeds in heavy work. Many newer trucks use the Detroit DT12 automated manual, and some vocational trucks use Allison automatics.
03VIN, engine serial and build sheet
Western Stars are often heavily customized for vocational and heavy-haul work. Build data tied to the VIN lists the original engine, transmission, PTO and other options. The engine serial confirms the exact engine version and emissions period.
04Aftertreatment, ECM, harness and cooling
On newer trucks, the engine works with its aftertreatment system, ECM and truck electronics. Replacement engines from a different emissions period or family can need different aftertreatment parts, harnesses or programming. Heavy-duty cooling packages and PTO setups are also common, so tell us how the truck is equipped.
05What to have ready
To get started, have:
- Full VIN
- Engine model and serial number
- Transmission model, serial and BOM if needed
- Truck model and year
- PTO and vocational equipment details
FAQ
Western Star engine & transmission questions
What engine is in my Western Star?
Newer Western Stars often have Detroit engines, while many have Cummins and some older trucks have Caterpillar or Series 60. Check the engine tag or VIN build data.
Can you find an 18-speed for my heavy-haul Western Star?
Yes. Send the transmission tag details, including model and BOM, and we search supplier sources for a matching unit.
Is a Western Star engine the same as a Freightliner engine?
Both are Daimler Truck brands and often share Detroit engines, but installation, electronics and options can differ. We match by VIN and engine serial.
My truck has PTO equipment. Does that matter?
Yes. PTO provisions on the engine or transmission need to match. Tell us what PTO equipment you run.
Are you a Western Star dealer?
No. We are an independent sourcing company. We search supplier sources nationwide and confirm availability and freight on your quote.
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Ready when you are
Replacing the engine or transmission in your Western Star? Start with the VIN.
Have your engine serial number, CPL and VIN handy. If you don't, we'll help you find them.
Commercial-Engines.com is an independent supplier of used commercial truck engines and transmissions. Manufacturer names, model names and part numbers are used for identification only and do not imply affiliation with, or endorsement by, any manufacturer. Read the full disclaimer.