Eaton Detroit Truetrac Differential 09-23 Ford F-150 4x4 Front Axle 31 Spline 8.8in All Ratios
Put a 2009-2023 F-150 in 4WD on a muddy two-track or a snowy hill and the open front 8.8 does what open diffs do: one front tire spins and the truck stops pulling. The Eaton Detroit Truetrac 917A738 is a gear-driven limited slip built for the Ford 8.8 inch independent front axle with 31-spline stub shafts, in all gear ratios. It gives the front end real pulling power in 4WD while staying smooth and quiet in daily 2WD driving, with no clutches to wear and no air or electric lines to run.
The front 8.8 on these trucks is a reverse-rotation axle mounted to the frame, with half-shafts out to the wheel ends. An open carrier splits torque evenly, so the side with the least grip limits how hard the truck can pull. The Truetrac replaces the spider gears with sets of helical pinions that ride in pockets in the case. When one tire starts to slip, the gear separating forces press the pinions into their pockets and the friction biases torque toward the tire with more grip. It works in forward and reverse, engages automatically, and has no clutch packs, so there is nothing to adjust or rebuild. Because it biases torque rather than locking, a tire hanging fully in the air can still spin; a light touch of the brake usually brings the other side back into play.
Make sure the noise or traction problem is really in the front diff. Grinding in 2WD on these trucks is usually the vacuum-controlled IWE hubs, not the carrier, and our Ford 8.8 IFS front differential guide explains how to separate hub, half-shaft and carrier problems. Confirm 31-spline stubs: earlier fronts through 2008 used 28-spline shafts and do not take this unit. The Detroit Locker vs Truetrac guide and the Truetrac buyers guide by axle and spline help if you are still choosing.
This listing is for the 2009-2023 Ford F-150 4x4 front 8.8 inch reverse-rotation axle with 31-spline axle shafts, and Eaton rates it for all ratios, so it accepts the factory gears or a regear. Eaton specifies a 1.32 inch axle shaft diameter. Expedition and Navigator trucks of the same years share a similar front axle, but they are not on our fitment list, so send us the year, VIN and axle code before ordering for one of those. It does not fit any rear 8.8 axle, the 2008-and-older 28-spline fronts or Super Duty solid axles. Browse more traction options in our hard parts category.
The carrier comes out of the front housing after the half-shafts and the cover are off. Mark the bearing caps, pull the carrier and press off the bearings with a puller such as the OTC 4520 side bearing puller set. Move the ring gear to the Truetrac with new bolts and thread locker, fit new carrier bearings, then set preload and backlash to the gear maker's spec and read the pattern on both sides of the teeth, since reverse-rotation gears load the opposite face from a rear axle. If you are regearing for bigger tires, the Yukon 4.56 reverse-rotation 8.8 gear set or the 4.88 set fit this axle, and the front must match the rear ratio exactly. Eaton calls for a quality petroleum-mineral GL-5 80W-90 gear oil and says synthetic oils and friction modifiers should not be used.
| Brand | Eaton |
| Part number | 917A738 |
| Fits | Eaton Detroit Truetrac Differential 09-23 Ford F-150 4x4 Front Axle 31 Spline 8.8in All Ratios |
| Vehicle fitment | Ford F-150 4X4 (2009-2023) |
| Type | Differentials |
| Condition | New |
| Ships | Same business day (in stock), from the USA |
| Warranty | 1-year |
Doing this repair right usually means replacing these at the same time. Same transmission, ships together.
No. Through 2008 the F-150 front 8.8 used 28-spline axle shafts. This Truetrac is the 31-spline version for the 2009 and newer front axle.
Yes. Eaton rates the 917A738 for all ratios, so you can keep the factory gears or regear to 4.10, 4.56 or 4.88 to match the rear.
No. Eaton says to use a petroleum-mineral GL-5 80W-90 gear oil and not to use synthetic oils or friction modifiers with this unit.
It only biases torque when the front axle is driving in 4WD and a tire starts to slip, so in 2WD there is no change. In 4WD it is milder than a locker in turns.
No. The front 8.8 is a reverse-rotation axle with its own carrier. Rear 8.8 axles need a rear Truetrac or limited slip with the correct spline count.
New carrier bearings, ring gear bolts and fresh gear oil at minimum. If the pinion whines on decel, replace the pinion bearings and seal as well.
