Yukon Gear Round Replacement Yoke Companion Flange For Dana 80

A Ford F-350 dually or F-450 Super Duty that drips gear oil from the front of the rear axle, clunks when the transmission engages, or shakes at highway speed may need a new pinion flange. This is the Yukon Gear and Axle YY D80-RND-37R, a round companion flange with a 37-spline bore for the Dana 80 rear axle. It replaces the round, bolt-on style flange Ford used on its Dana 80, cross-referenced to Ford BC3Z-4851-B and the discontinued Dana Spicer 84794.

What the companion flange does in a Dana 80

Most axles use a pinion yoke with ears that hold a U-joint. The Ford Dana 80 instead uses a round companion flange: a flat, round face that the driveshaft's flange yoke bolts to. The flange is splined to the 37-spline pinion and clamped by the pinion nut, and its hub is the surface the pinion seal runs on. A machined male pilot on the face centers the driveshaft so it runs true. Published dimensions for this flange are a 2.953 inch male pilot and a 2.500 inch seal hub, and it mates to a 1410 or 1480 series flange yoke on the driveshaft side. The Dana 80 is a big ring gear axle built to carry heavy loads, and the flange is a common replacement when the seal surface wears or the splines loosen under towing.

Symptoms of a worn flange

• Gear oil leaking from the pinion seal and slinging onto the driveshaft and frame, returning soon after a seal replacement because the hub is grooved
• A clunk when shifting into drive or reverse, or on and off the throttle, from loose or worn splines
• Driveline vibration at speed from a damaged pilot or face that no longer centers the shaft
• Pinion bearing noise along with the leak, a common Dana 80 wear pattern on high-mileage tow rigs

How to confirm before buying

Look at the front of the axle. A round flange with the driveshaft bolted face to face is this style. If the driveshaft U-joint sits in ears held by straps or U-bolts, you have a yoke and need the Dana 80 1410 yoke instead. Unbolt the driveshaft and check the flange for rotational play on the pinion, and feel the hub behind the seal for a groove. Any in-and-out play of the pinion itself means the bearings need attention, and a Dana 80 master overhaul kit is the right repair.

Fitment

This flange fits the Dana 80 rear with a 37-spline pinion and a round companion flange. Retail fitment lists it for Ford F-350 Super Duty (including 2011-2015 models) and F-450 Super Duty pickups with the Dana 80, and the Ford service number it replaces, BC3Z-4851-B, is a Super Duty part. Ford Dana 80 axles changed over the years, so check that your pinion has 37 splines and a round flange, or send us your year and VIN to confirm. More Dana 80 parts are in our hard parts collection.

Install notes

• Mark the driveshaft flange to the companion flange so the shaft goes back in the same position
• Mark or measure the pinion nut position before removal, then use a puller to remove the old flange
• Always fit a new pinion seal. Yukon's YMS100727 seal is listed for 1998-up Ford flanged-style Dana 80 axles with the 4.375 inch OD pinion bearing. If the carrier bearings are noisy too, the Dana 80 carrier bearing kit handles that side of the job
• Clean the pilot and mating faces so the driveshaft seats flat, and torque the flange bolts and pinion nut to the factory spec
• Refill with 75W-90 or 75W-140 gear oil, plus friction modifier if the axle has a limited slip

What does this flange replace?

It is cross-referenced to Ford service part BC3Z-4851-B and the discontinued Dana Spicer 84794, the round companion flange on the Ford Super Duty Dana 80 rear.

How do I know if I need a round flange or a yoke?

If the driveshaft bolts face to face onto a round plate at the axle, you need this flange. If the U-joint sits in two ears held by straps or U-bolts, you need a Dana 80 yoke in 1410 or 1480 size.

What driveshaft does it work with?

It mates to a 1410 or 1480 series flange yoke on the driveshaft. It has a 2.953 inch male pilot that centers the driveshaft.

Should I replace the pinion seal too?

Yes. Fit a new seal any time the flange comes off. For 1998-up Ford Dana 80 axles with the 4.375 inch OD pinion bearing, Yukon's flanged-style seal is the match.

Can I use it to convert a yoke-style Dana 80?

It has the same 37-spline bore, so it can be used to convert a yoke-style Dana 80 to a flange, but you will also need a matching flange yoke on the driveshaft. Confirm your pinion is 37 spline first.