Yukon Gear Grizzly Locker For GM 8.5in & 8.6in / 30 Spline / 2.73+

Yukon Gear Grizzly Locker for GM 8.5 Inch and 8.6 Inch Differential with 30 Splines for 2.73 and Up Ratios

The YGLGM8.5-3-30 is an automatic locking differential engineered for the GM 8.5 inch and 8.6 inch 10-bolt rear axle housing using 30 spline axle shafts. Covering an extensive list of GM cars, trucks, vans, and SUVs from 1980 through 2017, part number YGLGM8.5-3-30 works with gear ratios of 2.73 and numerically higher. The Grizzly Locker locks both rear wheels together under throttle torque and releases smoothly when power is lifted during turns, providing maximum traction across a wide variety of street and off-road applications. The YGLGM8.5-3-30 fits the same carrier bore as the factory open unit, making installation straightforward.

Features and Benefits

• Fits GM 8.5 inch and 8.6 inch 10-bolt rear differentials with 30 spline axles
• Compatible with gear ratios 2.73 and numerically higher
• Fully automatic mechanical lockup requires no driver action
• Covers Silverado, Sierra, Tahoe, Yukon, Suburban, S10, Colorado, Canyon, and more
• Direct-fit drop-in to the existing open carrier bore
• High-strength machined steel construction for demanding use
• Releases smoothly on pavement during cornering for normal street drivability
• Backed by Yukon Gear manufacturer limited warranty

Vehicle Fitment

Specifications

What Is Included

• One Grizzly Locker differential assembly (YGLGM8.5-3-30)
• All cam and driver internal components
• Installation instruction sheet

Frequently Asked Questions

Will installing YGLGM8.5-3-30 affect my factory warranty?
The Magnuson-Moss Warranty Act protects you from blanket warranty denials caused solely by aftermarket part installation. Your dealer must demonstrate the part directly caused the failure in question.

How do I confirm my GM axle is an 8.5 or 8.6 inch and uses 30 splines?
The GM 8.5 inch and 8.6 inch 10-bolt axles are commonly found in 1999 and newer Silverado 1500, Sierra 1500, Tahoe, Yukon, and Suburban trucks. The 8.6 inch replaced the 8.5 inch around 1999. Both use the same 30 spline axle shaft. Count the splines on your axle shaft to confirm before ordering YGLGM8.5-3-30.

What gear ratios are compatible with YGLGM8.5-3-30?
This Grizzly Locker requires a 2.73 or numerically higher ratio in the GM 8.5 or 8.6 inch housing. It will not fit the low-carrier break housing used with ratios below 2.73.

Does the Grizzly Locker work differently than a posi or limited-slip unit?
Yes. A Grizzly Locker is a fully automatic mechanical locker, not a limited-slip clutch pack. It provides 100 percent lockup under torque rather than a percentage of torque transfer. It clicks during cornering, which is normal.

Can I install YGLGM8.5-3-30 myself?
Professional installation is recommended. Setting carrier bearing preload, ring gear backlash, and contact pattern requires specialized tools and experience. Improper setup can damage the ring and pinion.

What fluid does the GM 8.5/8.6 axle require with a Grizzly Locker?
Use 75W-90 or 80W-90 full synthetic GL-5 gear oil. Do not add limited-slip friction modifier. If your vehicle previously had a limited-slip, flush the housing completely before installing YGLGM8.5-3-30.

Is there anything special about installing this in a 4WD versus 2WD truck?
Installation procedure is the same for both. On 4WD trucks, ensure the front and rear differentials are in the same or compatible ratio. Mixing ratios in a part-time 4WD system can cause driveline binding.

What warranty does YGLGM8.5-3-30 carry?
Yukon Gear provides a manufacturer limited warranty against defects in materials and workmanship from the date of purchase. Keep your receipt and have installation performed by a qualified shop to maintain coverage.

Installation Instructions

1. Raise and support the vehicle safely. Drain the differential oil.
2. Remove the rear axle shafts by unbolting the retainer flanges at the axle tube ends.
3. Remove the differential cover and clean the sealing surface.
4. Mark and remove the carrier bearing caps. Note shim positions and thickness.
5. Remove the existing open carrier from the housing.
6. Press the ring gear off the old carrier. Press off the carrier bearings.
7. Press the ring gear onto the YGLGM8.5-3-30 Grizzly Locker. Torque ring gear bolts to GM specification.
8. Press new carrier bearings onto the Grizzly Locker assembly.
9. Install the Grizzly Locker in the housing and set bearing caps finger-tight.
10. Adjust backlash to 0.005 to 0.009 inch using shims. Verify with a dial indicator.
11. Verify gear contact pattern with marking compound. Adjust shims to correct the pattern if needed.
12. Torque bearing cap bolts to GM factory specification.
13. Install the cover with new RTV or gasket, torquing to specification.
14. Reinstall axle shafts and torque retainer bolts to specification.
15. Fill to proper fluid level and road-test. Check for leaks after 50 miles.

Proposition 65 Warning: This product can expose you to chemicals including lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.p65warnings.ca.gov.