Yukon Gear Grizzly Locker / Ford 8.8in w/ 31 Splines

Yukon Gear Grizzly Locker for Ford 8.8 Inch Differential with 31 Spline Axles

The YGLF8.8-31 is a full-strength automatic locking differential built for the Ford 8.8 inch rear axle housing using 31 spline axles. Covering an enormous range of Ford cars, trucks, vans, and SUVs spanning more than three decades, the YGLF8.8-31 Grizzly Locker delivers instant, 100 percent lockup under throttle while releasing smoothly during normal turning. Whether your application is a classic Mustang, a daily-driven Ranger, a heavy-duty Bronco, or an Explorer used for off-road trail work, part number YGLF8.8-31 offers the same mechanical reliability that Yukon Gear is known for.

Features and Benefits

• Designed specifically for the Ford 8.8 inch rear differential with 31 spline axles
• Automatic mechanical lockup activates under torque with zero driver input required
• Precision-machined alloy steel construction for long service life
• Covers Ford Mustang, F-150, Ranger, Bronco, Explorer, Crown Victoria, and more
• Disengages during turns to allow normal on-road driving behavior
• Direct-fit drop-in replacement for the stock open carrier
• Compatible with ring and pinion ratios from 2.73 and up
• Backed by Yukon Gear manufacturer limited warranty

Vehicle Fitment

Specifications

What Is Included

• One Grizzly Locker differential assembly (YGLF8.8-31)
• Internal cam and driver hardware
• Installation instruction sheet

Frequently Asked Questions

Does installing YGLF8.8-31 void my factory powertrain warranty?
Under the Magnuson-Moss Warranty Act, your dealer must demonstrate that the aftermarket part directly caused the failure before denying warranty coverage. Installing YGLF8.8-31 alone does not automatically void your warranty.

How do I identify whether my Ford has a 28 spline or 31 spline 8.8 axle?
Most V8-equipped Mustangs, F-150 trucks, Broncos, and full-size Explorers use 31 spline axles. Four-cylinder Rangers and smaller applications typically use 28 spline axles. Count the splines on the axle shaft or reference your VIN and axle code on the door jamb sticker.

Will YGLF8.8-31 fit both 28 spline and 31 spline axle housings?
No. YGLF8.8-31 is designed exclusively for 31 spline axles. For 28 spline Ford 8.8 inch applications, a separate locker part number is required.

What gear ratio range works with this locker?
YGLF8.8-31 is compatible with all ratios from 2.73 and numerically higher in the Ford 8.8 inch housing. This covers essentially every factory ratio offered in Ford 8.8 equipped vehicles.

Is there a break-in period for YGLF8.8-31?
Yukon Gear recommends a 500-mile break-in period avoiding extreme off-road use and trailer towing. Inspect fluid level and check for leaks after the break-in period and change the fluid at that time.

Can I still use traction control with a Grizzly Locker installed?
Electronic traction control systems may behave differently with a mechanical locker. On vehicles equipped with stability control, the system should still function but may apply brakes more aggressively. Some owners choose to disable traction control during off-road use.

What differential fluid should I use with YGLF8.8-31?
Use 75W-140 full synthetic or 80W-90 conventional gear oil meeting GL-5 specifications. Do not add limited-slip additive as this locker is not a friction-clutch type unit.

Is YGLF8.8-31 covered by a warranty?
Yes. Yukon Gear provides a manufacturer limited warranty covering material defects. Installation must be performed by a qualified technician following the included instructions to maintain warranty coverage.

Installation Instructions

1. Safely raise and support the vehicle. Remove the drain plug and drain the axle oil.
2. Remove the axle shafts by unbolting the retainer plate at each axle tube end.
3. Remove the differential cover and clean the housing mating surface.
4. Mark and remove the carrier bearing caps. Record shim thickness and position.
5. Lift the existing carrier assembly out of the housing.
6. Press off the ring gear and carrier bearings from the old carrier.
7. Press the ring gear onto the YGLF8.8-31 Grizzly Locker and torque ring gear bolts to Ford spec.
8. Press new carrier bearings onto the Grizzly Locker.
9. Install the Grizzly Locker in the housing and fit bearing caps loosely.
10. Set ring gear backlash between 0.005 and 0.009 inch with shims. Verify with a dial indicator.
11. Perform a gear contact pattern check with marking compound.
12. Torque bearing cap bolts to Ford factory specification.
13. Install the differential cover with new gasket or RTV sealant and torque to specification.
14. Reinstall axle shafts and torque retainer bolts to factory specification.
15. Fill to the correct fluid level and test-drive. Inspect 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.