Yukon Gear Flange Yoke For Ford 10.25in and 10.5in w/ Long Spline Pinion

On Ford Super Duty pickups and E-Series vans with the Sterling 10.25 inch or 10.5 inch rear, the driveshaft often bolts to a round companion flange on the pinion rather than dropping into a U-joint yoke. When that flange gets a worn seal track, a leaking pinion seal or a damaged bolt face, the YY F100606 from Yukon Gear and Axle is the replacement. It is a 31-spline round companion flange made for the long spline pinion, the taller pinion Ford introduced on the 10.25 in 1993 and carried into the 10.5.

What the companion flange does in a Sterling 10.25 or 10.5

The flange is splined onto the end of the pinion gear and clamped by the pinion nut. The driveshaft's own flange yoke bolts to its face, so all the torque from the transmission to the ring gear passes through it. Behind the face, the flange neck is the surface the pinion seal runs on. Yukon lists this part at 1.96 inches tall with a 1.63 inch through hole, sized for the long spline pinion. That spline length matters: according to Denny's Driveshafts, the 1985-1992 Sterling 10.25 used a 31-spline pinion with a short yoke height, while 1993-1998 10.25 and 1999-2010 10.5 axles used a 31-spline pinion with a tall yoke height. The first and second 10.25 designs are commonly called short pinion and long pinion axles, and the later version addressed a known, if rare, pinion nut loosening issue.

Symptoms of a worn flange

• Gear oil running down the nose of the housing and onto the driveshaft, even after a new pinion seal
• A visible groove or rust pitting on the flange neck where the seal lip rides
• Clunk on takeoff or when changing direction, from worn splines or a pinion nut that has backed off
• Vibration that rises with speed after a flange face was damaged or the driveshaft bolts loosened
• Stripped or elongated bolt holes on the flange face

How to confirm before ordering

Unbolt the driveshaft from the flange and support it out of the way. Wiggle the flange to check for spline slop or pinion end play, then turn it by hand and listen for rough bearings. Wipe the neck and inspect the seal track closely. Count the pinion splines and note your build date: 2011 and later Super Duty 10.5 axles use a 37-spline pinion, so this 31-spline flange is not the part for them. If the bearings are worn, combine this flange with a Yukon 2007-and-older Ford 10.5 master overhaul kit or, for a 10.25, the Ford 10.25 master overhaul kit.

Fitment

Yukon's product notes describe YY F100606 as fitting 1993-and-up Ford 10.25 and 10.5 axles with the long spline pinion. Its vehicle chart specifically lists the 2005-2007 F-250 Super Duty 4WD, 2005-2007 F-350 Super Duty 4WD and RWD, and 2005-2007 E-350 and E-450 Super Duty vans. Other long-pinion trucks may use it as well, but Ford fitted both companion flanges and U-joint yokes to these axles depending on the driveshaft, so check what is on your pinion first. It will not fit a 1985-1992 short pinion 10.25; for those axles see the Yukon short yoke for 1992-and-older Ford 10.25. When in doubt, send us the year, model and VIN or the axle tag code and we will verify. More heavy-duty axle parts are in our hard parts section.

Install notes

• Mark the driveshaft-to-flange position so the shaft bolts back in the same orientation.
• Measure pinion turning torque with an inch-pound wrench before removing the nut, then follow the factory pinion nut procedure for your axle on reassembly. Do not reuse a damaged nut.
• Install a new pinion seal, lubricate the lip with gear oil, and clean the flange face so the driveshaft seats flat.
• Torque the driveshaft bolts evenly in a crisscross pattern.
• Refill with the gear oil grade your owner's manual lists for the axle and add friction modifier if it has a clutch-type limited slip that calls for it. Replacing side bearings too? The Ford 10.25/10.5 carrier installation kit has the parts.

What is the difference between the long spline and short spline pinion?

Both are 31-spline, but the 1985-1992 Sterling 10.25 has a short pinion with a short yoke height, while 1993-up 10.25 and 10.5 axles use the longer pinion with a tall yoke. This flange is for the long pinion only.

Does it fit a 2011 or newer F-250 or F-350?

No. The 2011-up Ford 10.5 uses a 37-spline pinion. This flange has 31 splines.

Is this a U-joint yoke or a flange?

It is a round companion flange. The driveshaft bolts to its face instead of a U-joint sitting in ears on the pinion.

Which trucks does Yukon list for it?

The 2005-2007 F-250 and F-350 Super Duty and 2005-2007 E-350 and E-450 Super Duty. The product notes cover 1993-up long-pinion 10.25 and 10.5 axles generally, so confirm your pinion before ordering.

What else should I replace with it?

A new pinion seal every time, a new pinion nut if the old one is damaged, and fresh gear oil. Worn pinion bearings call for a master overhaul kit.