Yukon Gear High Performance Gear Set For 15+ Ford F-150 8.8in in a 3.73 Ratio
If you drive a 2015-or-newer F-150 or Mustang and the rear axle has started to whine on the highway, or you have stepped up to taller tires and the truck now feels flat leaving a light, this is the gear set built for your axle. The Yukon Gear & Axle YG F8.8-373-15 is a new 3.73 ratio ring and pinion made specifically for the updated Ford 8.8 rear, often called the Super 8.8, that Ford introduced for the 2015 model year. It is not interchangeable with the gears for older 8.8 axles, and that difference is the main thing to understand before you order.
The pinion gear is driven by the driveshaft and meshes with the large ring gear bolted to the differential carrier. The tooth count ratio between the two, here 3.73 to 1, decides how many times the driveshaft turns for each turn of the axles. A numerically higher ratio multiplies torque at the tires, which is how you get back the acceleration and towing pull lost to larger tires. Ford redesigned the 8.8 for 2015 with bigger bearings, a longer pinion, 34-spline axles and a 12-bolt cover, so the pinion in this set is cut to match: Yukon lists it with a 31-spline pinion and a 2.000 in. pinion bearing journal.
Read the axle code on the door sticker or the tag on the axle to find your current ratio, then decide how far you need to go. A 3.73 is a moderate step that suits trucks that came with a numerically lower ratio and now run slightly taller tires. If you are chasing noise rather than ratio, pull the 12-bolt cover, check backlash with a dial indicator and paint the teeth. A worn bearing with good-looking gears may only need the YK F8.8-D master overhaul kit. It also helps to know your transmission's gear spread; our 6R80 gear ratios and specs page shows how first gear and overdrive combine with the axle ratio on the six-speed trucks.
Yukon lists this set for the 2015-and-later Ford F-150 8.8 in. rear and the 2015-and-later Mustang IRS 8.8 rear, standard rotation. Identify the axle by the 12-bolt cover; the earlier axle uses a 10-bolt cover and needs the YG F8.8-373 gear set for pre-2015 axles instead. Front IFS 8.8 axles are reverse rotation and do not take this set. If you are unsure, send us your year and VIN before ordering and we will check it.
A ring and pinion change is a setup job, not a bolt-in. Plan on new pinion and carrier bearings, a pinion seal and fresh crush sleeve, which is why most installers order the master overhaul kit with the gears. Yukon's setup chart for the Super 8.8 calls for 15-25 in-lb of pinion bearing preload with new bearings, 0.006-0.011 in. backlash, 95 ft-lb on the ring gear bolts and 70 ft-lb on the bearing caps. A side bearing puller set makes pulling the carrier bearings far easier. Check the contact pattern with marking compound before final assembly. If you want traction while the axle is apart, the Yukon Trac Loc for the Super 8.8 fits the same 34-spline axles. Fill with the gear oil grade in your owner's manual, add friction modifier if you run a clutch-type limited slip, and follow Yukon's break-in: easy driving for the first 15-20 miles, let the axle cool, no towing for 500 miles, then change the oil.
| Brand | Yukon Gear & Axle |
| Part number | YG F8.8-373-15 |
| Fits | Yukon Gear High Performance Gear Set For 15+ Ford F-150 8.8in in a 3.73 Ratio |
| Type | Final Drive Gears |
| 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. This set is for the 2015-and-later 8.8 with the 12-bolt cover. A 2014-and-earlier F-150 with a 10-bolt cover needs the standard YG F8.8-373 set, which has a different pinion.
3.73 is a moderate ratio that suits a modest tire upgrade from a numerically lower factory ratio. Going to 35 in. tires or towing heavy usually calls for something deeper, such as 4.11. Tell us your tire size, engine and transmission and we can help you choose.
A master overhaul or install kit with new pinion and carrier bearings, races, shims, pinion seal, crush sleeve and ring gear bolts. Old bearings almost never go back in once the pinion depth changes.
Yes. On a 4x4 the front and rear ratios must match, or the transfer case and driveline will bind in 4WD. The front IFS 8.8 takes a reverse-rotation set in the same ratio.
Yes. Any ratio change throws off the speedometer and can affect shift timing, so plan on updating the tire size and axle ratio settings in the computer with a programmer or at a dealer after installation.
