Yukon Gear High Performance Gear Set For 10 & Down Ford 10.5in in a 3.73 Ratio
A Ford Super Duty, Excursion or E-series van that tows hard eventually wears out its rear gears, and the 10.5 in. rear axle under 1999-2010 F-250 and F-350 Super Duty trucks is no exception. When the rear end starts to whine at highway speed, or you pull the cover and find pitted teeth, the Yukon Gear & Axle YG F10.5-373-31 is a 3.73 ring and pinion built for that axle. The -31 in the part number refers to the 31 spline pinion used before Ford changed the design for 2011.
The Ford 10.5 is a heavy-duty rear built around a large 10.50 in. ring gear, which is what lets it carry trailer weight. The pinion turns 3.73 times for every turn of the axle shafts with this set. Yukon lists it with a 31 spline pinion and 12 ring gear bolts. Those details matter, because the 2011-and-newer 10.5 uses a 37 spline pinion and needs its own gear set, so this one is strictly for the earlier axle.
A 3.73 is a common middle ground on these trucks: enough reduction to get a loaded trailer moving without the engine screaming on the highway when empty. If the truck already has 3.73s, this is a like-for-like rebuild. If it has something else, you are changing ratio and the speedometer and shift calibration need updating afterward.
Separate gear noise from bearing noise first. Gear whine usually changes between pulling and coasting; a bearing growl is steadier and often gets louder when turning. Our Ford 10.5 rear axle problems guide walks through it, and our axle code and gear ratio guide shows how to read the door tag code and the axle tag to see what ratio the truck has now.
The fitment chart for YG F10.5-373-31 covers the Ford 10.5 rear in 1999-2010 F-250 and F-350 Super Duty (2WD and 4WD), 2000-2005 Excursion, 2003-2010 E-250 and 2002-2003 E-550, among others. The chart splits housings into 2007-and-older and 2008-2010 groups, and this gear set is listed for both. It does not fit 2011-and-newer 10.5 axles with the 37 spline pinion. Ford also used a 10.25 in. axle in the same era, so measure the ring gear or read the axle tag before ordering. If you are not sure which rear you have, send your year and VIN.
For deeper ratios on the same axle, see the 4.11 set or the 4.88 set. If you are running 10.25 gears in a 2008-up 10.5 housing, that is a different job that needs the 10.25-to-10.5 conversion spacer; this set is a native 10.5 gear and does not. On a 4x4, the front axle has to be geared to the same ratio. Browse more axle parts in differential hard parts.
The ring and pinion do not include bearings or a crush sleeve. Pair them with the Yukon YK F10.5-A master overhaul kit for 1999-2007 axles or the Revolution 10.25/10.5 master install kit. Yukon's setup chart for the Ford 10.25 and 10.5 lists a .025 in. OEM depth shim, 20-35 in-lb pinion bearing preload with new bearings (10-16 with used), 95 ft-lb ring gear bolts and 80 ft-lb bearing caps. Pinion depth comes first, then preload, then backlash and the contact pattern. Use thread locker on the ring gear bolts.
Fill with 75W-90 or 75W-140 gear oil, adding friction modifier if the axle has a clutch-type limited slip. These trucks tow, so take the break-in seriously: drive at least 500 miles before towing, make the first loaded trips short with cool-down stops, and change the oil after 500 miles.
| Brand | Yukon Gear & Axle |
| Part number | YG F10.5-373-31 |
| Fits | Yukon Gear High Performance Gear Set For 10 & Down Ford 10.5in 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. 2011-and-newer Ford 10.5 axles use a 37 spline pinion and need a different gear set. This one is for 1999-2010 axles with the 31 spline pinion.
Read the axle tag on the cover bolt or measure the ring gear diameter. The 10.5 carries a 10.50 in. ring gear. When in doubt, send us your year and VIN.
A master overhaul or install kit with pinion and carrier bearings, races, shims, crush sleeve and pinion seal. Inspect the axle shaft seals and wheel bearings while the truck is apart.
Yes, if you are changing ratio. The front and rear must match, or the transfer case binds in 4WD. A same-ratio rebuild of 3.73 gears does not affect the front.
Yukon's break-in calls for at least 500 miles of driving before towing, short first trips with the load and cool-down stops, and a gear oil change at 500 miles.
