N3-40-2512 Super Duty Solid Butt Fits Tube 2.500×0.120 Can Be Machined To Any Tube Size – HARDENED SPLINES 7.000″ End To Weld 8.876″

N3-40-2512 Super Duty Solid Butt Stub/Midship Shaft — 2.500x0.120 Tube, 16x1.500" Hardened Splines

The N3-40-2512 is a super duty solid-butt stub shaft for 2.500-inch OD by 0.120-inch wall driveshaft tube, with a 16-spline by 1.500-inch diameter hardened spline profile. This midship shaft serves as the intermediate component in a two-piece driveshaft assembly: the splined end engages the slip yoke or center support bearing bore, and the weld end is machined with a solid butt configuration for welding to the driveshaft tube. The solid butt design — as distinct from a hollow or tube-over butt — provides maximum weld joint strength at the tube interface.

The hardened spline designation on N3-40-2512 is a critical specification. Standard splines are machined from mild steel; hardened splines are induction-hardened or through-hardened to increase wear resistance and fatigue life under high-torque or high-cycle loading. For heavy-duty and severe-service applications, this is the correct specification — do not substitute a standard-spline stub shaft where hardened splines are called for. The 16-spline by 1.500-inch profile means the mating slip yoke must have an internal spline bore of 16 splines at 1.500-inch pitch diameter. A 16x1.375-inch slip yoke will appear similar but will not engage — the pitch diameter difference prevents engagement. The spline length is 7.000 inches per the Notes field (internal documentation references 6.530 as a secondary dimension — use 7.000-inch spline length as the governing specification). End-to-weld dimension is 8.760 inches; butt diameter at the weld joint is 2.270 inches.

Specifications

• Part Number: N3-40-2512
• Tube Diameter x Wall: 2.500" x 0.120"
• Spline Count x Diameter: 16 x 1.500"
• Spline Length: 7.000" (per notes)
• End to Weld: 8.760"
• Butt Diameter: 2.270"
• Butt Style: Solid Butt
• Spline Condition: Hardened Splines
• Style: Slip
• Bearing Diameter: N/A

Fitment & Installation Notes

Confirm the mating driveshaft tube is 2.500-inch OD by 0.120-inch wall before ordering N3-40-2512. The solid butt bore is machined to fit the 2.500-inch OD tube; a 2.500x0.083 tube has the same OD but thinner wall and different weld prep geometry — the thinner wall requires a different butt bore depth and may not achieve full weld penetration with a butt designed for 0.120 wall. Count the splines on the mating slip yoke — must be 16 splines at 1.500-inch pitch diameter. Confirm hardened spline compatibility: hardened splines must mate with a slip yoke that can accept the hardness differential without galling the yoke's internal spline surface.

The N3-40-2512 can be machined to fit other tube sizes as described in the product application data. If your application requires a different tube OD, the solid butt profile must be re-bored to the new tube OD — confirm this with a driveshaft shop before ordering. Do not attempt to weld a mismatched tube OD to the butt bore; the resulting eccentric weld will throw the assembly off balance regardless of subsequent balancing attempts.

After welding N3-40-2512 to the driveshaft tube, the complete assembly must be dynamically balanced before installation. The 8.760-inch end-to-weld dimension establishes the axial position of the weld joint relative to the splined end — verify this matches the overall length requirement of your midship shaft configuration. The spline end engages the slip yoke or center support bearing stub shaft bore; grease this interface at assembly and at each service interval per the slip yoke manufacturer's specification.

Explore related stub and midship shaft components including solid and hollow butt variants in multiple tube OD and spline configurations.