Yukon Gear Trac Loc Positraction / Ford Super 8.8in / 34 Spline / 15-20 F-150

Yukon Trac-Loc Limited-Slip Differential for Ford Super 8.8in, 34 Spline, 2015-2022 F-150

The YC F8.8-4-34T/L is a clutch-type Trac-Loc limited-slip differential engineered specifically for the Ford Super 8.8-inch independent rear suspension (IRS) aluminum differential housing found in 2015 through 2022 Ford F-150 trucks. This YC F8.8-4-34T/L unit accommodates 34-spline axle shafts and is compatible with 3.31 and numerically higher gear ratios, including the popular 3.55, 3.73, and 4.10 options. The YC F8.8-4-34T/L replaces an open or worn limited-slip carrier to restore the traction-biasing performance that keeps power going to the wheel with grip on pavement, gravel, and light trail surfaces. Nodular iron construction and forged 4320 chromoly spider gears with Raybestos composite clutches provide long service life and quiet street operation.

Features and Benefits

• Ford Super 8.8in IRS Specific Fit - The YC F8.8-4-34T/L is dimensioned for the aluminum independent rear suspension housing of the 13th generation F-150, ensuring a direct bolt-in replacement without modification.
• Nodular Iron Carrier Case - High-strength nodular iron withstands the flex and shock loading typical in truck applications better than standard grey iron.
• Forged 4320 Chromoly Spider Gears - Premium alloy steel provides superior fatigue strength and surface hardness compared to standard cast spider gears.
• Raybestos Composite Clutch Packs - Smooth, progressive engagement without chatter or grab, ideal for daily driver use in the F-150.
• 34-Spline Design - Matches factory F-150 Super 8.8 axle shaft spline count for direct installation compatibility.
• Completely Rebuildable - Clutch packs and preload springs are replaceable, allowing restoration of performance without a full carrier replacement.
• One-Year Warranty - Backed by Yukon against manufacturer defects.

Vehicle Fitment

Specifications

What is Included

• One YC F8.8-4-34T/L Trac-Loc limited-slip carrier assembly
• Pre-installed clutch packs and side gears
• Installation instructions and notes

Frequently Asked Questions

• Q: Which F-150 models use the Super 8.8in differential?
  A: The aluminum Super 8.8in IRS differential was introduced on the 2015 F-150. The YC F8.8-4-34T/L fits all 2015 through 2022 model year F-150 trims with the Super 8.8in rear axle.
• Q: Does the YC F8.8-4-34T/L work with a 3.15 gear ratio?
  A: No. This unit requires 3.31 or numerically higher gear ratios. It will not function correctly behind a 3.15 final drive ratio.
• Q: What is the difference between Trac-Loc and a locker?
  A: Trac-Loc is a clutch-type limited-slip that continuously biases torque toward the wheel with traction without locking both wheels together. A locker forces both wheels to spin at the same speed, which can cause binding on pavement.
• Q: Are carrier bearings included with the YC F8.8-4-34T/L?
  A: No. New carrier bearings and races are required for installation and must be purchased separately.
• Q: Does Yukon's warranty comply with the Magnuson-Moss Warranty Act?
  A: Yes. Written warranty terms ship with the unit in compliance with the Magnuson-Moss Warranty Act. A specific dealer or installer is not required to maintain warranty coverage.
• Q: What gear oil does the Super 8.8in use?
  A: Ford specifies a friction-modified 75W-140 full synthetic gear oil for the Super 8.8in differential. Always add the correct friction modifier when servicing the YC F8.8-4-34T/L.
• Q: Can the clutch packs be replaced?
  A: Yes. The YC F8.8-4-34T/L is fully rebuildable using Yukon clutch rebuild kits when the limited-slip function begins to diminish.
• Q: What is the spline count on the axle shafts?
  A: The Ford Super 8.8in uses 34-spline semi-floating axle shafts. Confirm 34 splines before ordering as older 8.8in variants use 28 or 31 splines and are not compatible.

Installation Overview

1. Raise and safely support the vehicle, drain the Super 8.8in differential fluid and remove the cover.
2. Remove the rear axle shafts and carrier assembly, noting all bearing cap markings and shim locations.
3. Press carrier bearings onto the YC F8.8-4-34T/L using a bearing press; do not reuse worn bearings.
4. Transfer the ring gear to the new carrier using thread-locking compound and torque bolts to Ford specification.
5. Install the carrier with original shim pack, set backlash per Ford specifications, and verify with a dial indicator.
6. Confirm gear contact pattern using marking compound; adjust shims as required before final assembly.
7. Reinstall the differential cover with a new gasket or RTV sealant.
8. Fill the differential with the specified gear oil and friction modifier, torque the fill plug, and check for leaks before returning to service.

California Proposition 65 Warning: This product can expose you to chemicals including lead and its compounds, which are known to the State of California to cause cancer and reproductive harm. For more information, go to www.P65Warnings.ca.gov.