Yukon Gear Yoke For 8.5in or 8.6in GM (Mech 3R) w/ A U/Joint Size and Triple Lip Design

Plenty of GM trucks, SUVs and rear-drive cars with the 8.5 inch or 8.6 inch ten-bolt rear do not use a 1310 or 1350 joint at the pinion at all. They use the smaller Mechanics 3R joint with inside snap rings, and a yoke for any other joint size simply will not accept the driveshaft. The Yukon Gear and Axle YY GM12470387 is a new 30-spline, strap-style pinion yoke built for that Mechanics 3R joint, sold as a triple lip design, and it covers everything from a 1979 C10 to a 2017 Silverado 1500.

What this yoke does in a GM 8.5 or 8.6 rear

The yoke slides onto the 30-spline pinion, the pinion nut pulls it against the inner pinion bearing stack, and the driveshaft's rear U-joint bolts into the ears with two straps. The smooth neck behind the ears is where the pinion seal lip rides, so this one part both transmits all the driveline torque and keeps the gear oil inside the housing. What sets this yoke apart is the joint size. Yukon lists a 2.556 inch snap ring span and a 1.125 inch cap diameter with the snap rings on the inside of the ears. That is noticeably narrower than a 1350 joint, which spans 3.625 inches with 1.188 inch caps, as used by our cast 1350 GM 8.5 yoke.

Symptoms that send people looking for a 3R yoke

• A pinion seal leak that returns after a seal-only repair because the old yoke neck is worn through the seal track
• Clunk or slack felt on takeoff and when shifting between drive and reverse, from worn yoke or pinion splines
• Speed-related vibration after a failed U-joint wallowed out the cap seats in the ears
• Stripped strap bolt holes that will no longer hold torque
• Damage from a hammer-and-pickle-fork removal that bent the ears or scored the neck

How to confirm before you order

Unbolt the straps and lower the driveshaft. First identify the joint: if the snap rings sit inside the yoke ears and the caps measure about 1-1/8 inch, you have a 3R. Next, grip the yoke and feel for rotational play or end play. Free play with the yoke tight on the pinion usually means worn pinion bearings or a collapsed spacer, in which case plan a bearing job with a Timken GM 8.5 master bearing kit. Finally, check the seal surface for a ridge or pitting. Gear whine that changes on and off the throttle is a ring and pinion problem, not a yoke problem.

Fitment

Yukon's chart for YY GM12470387 is long. On the 8.5 inch side it includes 1970s and 1980s Chevrolet, Buick, Oldsmobile and Pontiac cars such as the Nova, Camaro, Firebird, Monte Carlo, Caprice, Impala, Cutlass, Regal, Grand Prix and Electra, plus C10, K10, K5 Blazer, C1500 and K1500 pickups, G-vans, Suburbans, the 1995-1998 Tahoe and 1992-1998 Yukon, and 1994-2004 S10 and Sonoma. On the 8.6 inch side it lists the 1999-2017 Silverado and Sierra 1500, Tahoe through 2017, Suburban and Yukon XL 1500 through 2014, Avalanche, Escalade, Express and Savana 1500, Colorado and Canyon 2004-2012, Trailblazer, Envoy, Rainier, Ascender, 9-7x, SSR and Hummer H3. GM changed driveshaft joints within some of these runs, so the yoke you need depends on the joint, not just the axle. Match the 3R inside-snap-ring joint and 30-spline pinion on your vehicle, or send the year, model and VIN and we will confirm. For other GM axle parts see our hard parts listings.

Install notes

• Paint-mark the driveshaft and yoke before removal to keep the shaft phasing the same.
• Read pinion rotating torque with an inch-pound wrench before you remove the nut. On a crush-sleeve axle, tighten only until that number is restored; going past it crushes the sleeve further and preloads the bearings too hard. A GM 8.5 crush sleeve eliminator is the cure if the sleeve is already over-crushed.
• Install a new pinion seal every time, lubricated with gear oil, and never reuse a damaged nut.
• Tighten the strap bolts evenly and confirm the joint snap rings are fully seated inside the ears.
• Top off with 75W-90 gear oil and add friction modifier for a clutch-type limited slip. On a 1999-2008 8.6 with high mileage, the GM 8.6 master overhaul kit covers the full bearing and seal set.

What is a Mechanics 3R U-joint?

A GM driveshaft joint with 1.125 inch bearing caps and inside snap rings. On this yoke the snap ring span is 2.556 inches. It is not interchangeable with a 1310 or 1350 joint.

Does it use straps or U-bolts?

Straps. The joint is held in the ears by two bolt-on straps.

Will it fit my 2012 Silverado 1500?

Yukon lists the 2009-2017 Silverado 1500 8.6 inch rear, as long as your driveshaft uses the 3R joint. Some trucks use a different joint, so check the snap ring style or send us your VIN.

How many splines does it have?

30 splines, which matches the GM 8.5 and 8.6 pinion it is listed for.

What should I replace along with the yoke?

A new pinion seal, a new pinion nut if the old one is damaged, and the gear oil. If the pinion bearings are loose or noisy, do the bearings at the same time.