Dana Spicer 4-1-6051X 1550 Series Companion Flange Assembly
The Dana Spicer 4-1-6051X Companion Flange Assembly is a heavy-duty driveline flange designed to provide a secure connection between a compatible transmission output shaft and the vehicle’s driveshaft assembly. Engineered to Spicer dimensional specifications, the 4-1-6051X combines a precision-machined splined bore, male pilot, and four-stud mounting pattern for reliable torque transfer in demanding commercial truck and drivetrain applications.
Dana’s Spicer driveline catalog identifies the 4-1-6051X as a 1550 Series companion flange assembly featuring a 1.998-inch major-diameter, 38-tooth involute spline. The assembly uses a 3.750-inch male pilot, a 4.750-inch bolt circle, and four 0.500-inch drilled mounting locations.
The companion flange mounts directly to the splined output shaft of the applicable transmission or driveline component. Its machined flange face then provides the connection point for the mating flange yoke or driveshaft assembly. This type of connection is commonly used where a bolted flange interface is preferred over a conventional exposed end-yoke connection.
Key Specifications
- Manufacturer: Dana / Spicer
- Part Number: 4-1-6051X
- Product Type: Companion Flange Assembly
- Driveline Series: Spicer 1550 Series
- Spline Type: Involute
- Spline Major Diameter: 1.998 in.
- Spline Count: 38
- Pilot Type: Male
- Pilot Diameter: 3.750 in.
- Bolt Circle Diameter: 4.750 in.
- Bolt Hole Diameter: 0.500 in.
- Number of Mounting Positions: 4
- Ground Hub Diameter: 2.750 in.
- Length Through Hole: 2.062 in.
- Flange Face to End of Hub: 3.875 in.
- Flange Configuration: Figure 1
- Component Flange Number: 4-1-6041
- Mounting Hardware Included: Four 8-73-226 studs
Dana’s companion-flange catalog specifically notes that the 4-1-6051X assembly includes four 8-73-226 studs, distinguishing the complete assembly from the underlying 4-1-6041 companion flange.
Heavy-Duty Transmission Output Application
The 4-1-6051X appears in Spicer transmission component documentation as a companion-flange option for several heavy-duty transmission families. For example, Spicer literature for the ES60-5, ES62-5, and CM55 transmission families lists the 4-1-6051X among the available transmission companion flange assemblies.
In these applications, the companion flange serves as an important interface between the transmission output shaft and driveshaft, allowing rotational power from the transmission to be transferred into the vehicle’s driveline. Correct spline engagement, pilot fit, flange dimensions, and driveline-series compatibility are essential for maintaining alignment and minimizing vibration under load.
Built for Spicer 1550-Series Drivelines
The Spicer 1550 Series is commonly used in heavy-duty commercial driveline systems where high torque capacity and durable component construction are required. The precision-machined splines and pilot surfaces of the 4-1-6051X help maintain proper concentricity between the transmission output and driveshaft connection, while the four-stud flange arrangement provides a strong, serviceable mechanical connection.
When replacing a companion flange, verify the 38-spline configuration, 1.998-inch spline diameter, 3.750-inch male pilot, 4.750-inch bolt circle, 1550 Series driveline, and transmission assembly number before ordering.
The Dana Spicer 4-1-6051X Companion Flange Assembly is an OE-style solution for compatible heavy-duty transmission and driveline applications requiring a 1550 Series, 38-spline output flange assembly with mounting studs included.
