Older transmissions (like the AT545, MT643, or HT740 series) use an older format.
Soon, a technician will tap their phone against the transmission case, and the serial number—along with real-time oil life data and fault history—will pop up on the Allison Service app. However, for the millions of 1000, 2000, 3000, and 4000 series units on the road today, the manual lookup remains a necessary skill. Allison Transmission Serial Number Lookup
Several independent heavy-duty parts websites (like Weller Truck Parts or Midwest Transmission ) offer free serial number decoders. Older transmissions (like the AT545, MT643, or HT740
Allison transmission serial numbers are stamped onto a metal identification tag riveted to the transmission housing. The location of this tag depends on the generation and family of your transmission. Older transmissions (like the AT545