How to Identify an Eaton Fuller Transmission
To identify an Eaton Fuller transmission, find the identification tag on the transmission case and record the model number, serial number, and any bill of materials or assembly number. The model number generally encodes the transmission family, torque rating, and number of forward speeds, which are the key details for matching a used replacement.
01Find the identification tag
Eaton Fuller transmissions typically have a metal identification tag riveted to the case. On many models it is on the side of the main case, but location varies by model and generation, and it may be hidden by dirt, a crossmember, or wiring.
Clean the tag carefully. Stamped characters can be faint, and a wire brush can make them worse. A rag with degreaser and a flashlight held at a low angle often makes faded characters readable. Take a photo.
- Check the side of the main case first
- Look near the front and rear of the case if not found
- Clean with degreaser, not a wire brush
- Photograph the whole tag in good light
02Record every number on the tag
The tag typically lists a model number and a serial number, and may also carry a bill of materials or assembly number. Record all of them. The model number tells you the family and type; the serial and assembly numbers help pin down the exact build.
Two transmissions with the same model number can still differ in input shaft, clutch housing, shift tower, PTO provisions, and other details. The extra numbers help sort that out.
03How to read a Fuller model number
Eaton Fuller model numbers follow a pattern of letters, then numbers. The letter prefix describes the family and design features, such as Roadranger, twin countershaft, or overdrive. In many common models, the numbers encode the torque rating and number of forward speeds.
For example, in a model like RTLO-16918B, the 16 is commonly read as a torque capacity of roughly 1,650 lb-ft, and the 18 as the number of forward speeds. The trailing letter often indicates a design level or revision. Treat this as a general guide and confirm the specific model with Eaton documentation or a dealer.
- Letter prefix: family and design features (for example RT, RTLO, FRO)
- First number group: commonly the torque capacity in hundreds of lb-ft
- Last two digits: commonly the number of forward speeds (10, 13, 15, 18)
- Trailing letter: commonly a design level or revision
04Manual vs automated Eaton models
Eaton built both manual and automated transmissions. Automated models, such as UltraShift PLUS and Endurant, have different model prefixes and electronic controls. If your truck has no clutch pedal, or a clutch pedal used only for starting and stopping, check whether you have an automated unit.
Automated transmissions also need the right controls, harness, and software to work with the truck. That makes exact identification even more important than with a manual.
05Other details that affect fit
Beyond the model, a few details determine whether a transmission bolts in and works without modification. Note them while you are under the truck.
Photos of the clutch housing, shift tower, rear yoke, and any PTO help a sourcing team compare candidate units against yours without guessing.
- Clutch housing and input shaft size
- Shift tower type and shifter location (forward or standard position)
- Rear output yoke or flange type
- PTO openings and whether a PTO is installed
- Speed sensors and their connectors
- Truck VIN, year, make, and engine model
FAQ
Frequently asked questions
What if the Eaton tag is missing?
Check the case for cast or stamped numbers, look through the truck's build sheet or repair records, and ask a dealer to look up the original transmission by VIN. Count the forward speeds and note the shift pattern as additional clues.
Are all 18-speeds the same?
No. Torque rating, design level, input shaft, clutch housing, and other details vary. Match the model and assembly numbers whenever possible.
What does the O in RTLO mean?
In Eaton Fuller naming, the O commonly indicates an overdrive model. Confirm with Eaton documentation for your specific model.
Ready for a quote?
Get a transmission quote
Tell us the truck and the unit. We'll search suppliers nationwide and quote a specific match.