6.3-86-18S 1710/1760 Threaded Rubber Dust Cap for 2.500×16

6.3-86-18S UDS 1710/1760 Series Threaded Rubber Dust Cap — 2.500x16 Spline

The 6.3-86-18S is a UDS threaded rubber dust cap for 1710 and 1760 series slip yoke applications with a 2.500x16 spline stop shaft — 2.500-inch diameter, 16 splines. This screw-on rubber cap seals the open end of the slip yoke spline bore cavity, preventing water and contamination from reaching the stop shaft splines and yoke internal splines. The 1710 and 1760 series are adjacent in Spicer's capacity hierarchy, and this cap is sized for the 2.500-inch stop shaft diameter common to both.

The 2.500x16 spline dimension is the critical fitment parameter for 6.3-86-18S. The stop shaft diameter determines the bore into which the cap must thread — a 3.000x16 shaft (1810 series) uses a larger threaded bore, and the 2.500x16 cap will not engage its threads. Conversely, a 2.000x16 shaft (1610 series) has a smaller bore, and the 6.3-86-18S will be loose and leak. Measure the stop shaft with a caliper to confirm 2.500-inch diameter before ordering. The threaded rubber design provides secure retention in high-vibration commercial applications and allows hand removal for spline inspection without specialized tools. The 1710 series uses a 1.938-inch U-joint cap diameter; the 1760 is a variant with differing flange or yoke geometry in some configurations — confirm the stop shaft dimension is the governing spec for this cap selection, not the U-joint series alone.

Specifications

• Part Number: 6.3-86-18S
• Brand: UDS
• Series: 1710, 1760
• Spline Spec: 2.500" diameter x 16 splines
• Type: Threaded Rubber Dust Cap
• Retention: Screw-on (threaded)

Fitment & Installation Notes

Measure the stop shaft diameter with a caliper to confirm 2.500 inches before ordering 6.3-86-18S. Count the splines to confirm 16; some 1710 series variants use different spline counts in specific OEM configurations. Inspect the yoke bore opening for thread engagement features — threaded dust cap seats have a visible helical thread cut into the bore lip. If the bore is smooth, the slip yoke uses a press-on cap, not the threaded 6.3-86-18S.

Replace 6.3-86-18S at any sign of rubber hardening, cracking, or bore lip damage. A compromised dust cap on a 1710/1760 series yoke in a commercial truck application can allow corrosion to progress to spline seizure, preventing the driveshaft from telescoping and creating a solid connection that transmits chassis flex directly to the driveshaft tube — leading to tube failure. Thread the cap on by hand, do not over-torque, and verify the cap face is square to the yoke bore opening after installation.

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