6.5-86-38S UDS 1810 Threaded Rubber Dust Cap for 3.000×16

6.5-86-38S UDS 1810 Series Threaded Rubber Dust Cap — 3.000x16 Spline

The 6.5-86-38S is a UDS threaded rubber dust cap designed for 1810 series slip yoke applications with a 3.000x16 spline specification — a 3.000-inch diameter, 16-spline stop shaft. This cap threads onto the open end of the slip yoke to seal the spline bore cavity against water, mud, and road debris that cause fretting corrosion on the stop shaft and yoke splines. The threaded retention design (screw-on) provides a more secure seal than press-on caps in high-vibration and off-road environments.

The 3.000x16 spline designation identifies the stop shaft this cap is designed to fit: 3.000-inch major diameter with 16 splines. The 1810 series uses large-diameter, high-spline-count shaft profiles to handle the elevated torque loads in heavy commercial applications. A 2.500x16 stop shaft cap will not thread correctly onto a 3.000x16 bore — the thread pitch and bore diameter are specific to the shaft diameter. The rubber material allows the cap to compress slightly against the yoke bore lip, creating a positive seal against moisture intrusion. At 1810 series torque levels, spline corrosion from a failed or missing dust cap can progress to spline seizure within a single winter season in wet climates.

Specifications

• Part Number: 6.5-86-38S
• Brand: UDS
• Series: 1810
• Spline Spec: 3.000" diameter x 16 splines
• Type: Threaded Rubber Dust Cap
• Retention: Screw-on (threaded)

Fitment & Installation Notes

Before ordering 6.5-86-38S, confirm the slip yoke stop shaft is 3.000-inch diameter with 16 splines. Count the splines on the stop shaft directly — do not rely on vehicle application data alone, as some vehicles use different spline counts within the same series designation. Confirm the yoke bore uses a threaded dust cap seat by inspecting the open end for thread engagement features. A yoke with a press-on seat requires a press-on cap, and the threaded 6.5-86-38S will not seal correctly on a smooth bore.

The 1810 series is standard in Class 6–7 heavy commercial truck driveshaft applications. Dust cap replacement is a maintenance item — inspect 6.5-86-38S at every driveshaft lubrication service and replace if the rubber shows hardening, cracking, or tear at the bore lip. Thread the cap in by hand until snug; rubber caps do not require tool tightening, and over-torquing can tear the rubber at the thread root.

After installing 6.5-86-38S, verify the cap seats fully without cross-threading by confirming the cap face is parallel with the yoke bore opening. A cocked cap will leak around the bore lip despite appearing installed. Confirm the stop shaft slides freely in the yoke with the cap installed — the cap must not contact the stop shaft or restrict telescoping travel.

Explore related slip yoke components including 1810 series slip yokes and matching U-joints for complete service.