Yukon Gear Conversion Spacer To Use 10.25in Ring & Pinion in 08+ 10.5in Housing

If you own a 2008, 2009 or 2010 Ford Super Duty or E-series with the 10.5 inch Sterling rear and the gear set you want is a 10.25 set, this small part is what makes the swap work. The Yukon Gear and Axle SK F10.5-CONV is a conversion spacer for installing a Ford 10.25 ring and pinion in a 2008-and-later 10.5 housing. It is the part regear shops and owners go looking for when a 10.25 gear set does not set up correctly in the newer housing.

What the conversion spacer does in a Ford 10.5

The Sterling 10.25 and 10.5 share a layout: a 12-bolt cover, 35-spline full-floating axle shafts, and threaded adjusters that position the carrier instead of shims. Ford enlarged the ring gear to 10.5 inches around the 1998-1999 model years and then changed the housing again for 2008. Because of that 2008 change, a 10.25 gear set does not drop into the newer case and set up the way it would in an older one. Yukon's spacer, listed at 0.120 in thick, makes up that difference so the 10.25 ring and pinion can be installed and set to spec in the 2008-2010 10.5 housing. Yukon's description of the part is short: it is used to install a Ford 10.25 ring and pinion set into a 2008-2010 Ford 10.5 housing.

Signs you need it

• You are regearing a 2008-2010 10.5 Sterling and the ring and pinion you bought or have on hand is a 10.25 set
• A 10.25 set test-fit in an 08-10 housing will not reach a usable pinion depth or contact pattern with normal shims
• You are rebuilding a truck whose axle was regeared before and the previous builder used 10.25 gears

The spacer does not fix noise by itself. If the axle howls under load, goes quiet on coast, or the yoke has play, those are pinion bearing problems first, and the Ford Sterling 10.5 problems and rebuild guide covers how they develop on towing trucks.

How to confirm before ordering

Confirm three things: that the axle is a Sterling and not a later Dana-built rear (read the axle tag or the door sticker axle code), that the housing is a 2008-2010, and that your gear set is a 10.25 part number. Our guide on finding your rear axle ratio and axle code shows where to look. If the noise you are chasing could be the transmission rather than the axle, check transmission versus differential noise before tearing anything down.

Fitment

Yukon lists this spacer for using a Ford 10.25 ring and pinion in a 2008-and-up 10.5 housing, and its fitment notes narrow it to 2008-2010 10.5 housings. That cut-off matters: 2011-and-later trucks use a different pinion with a 37-spline flange, so they take 2011-up gear sets and parts rather than this conversion. Earlier 10.5 axles from before the 2008 housing change do not need it. If your truck sits on a model year boundary or has had its axle swapped, send us the year, VIN and axle tag before ordering. Other Sterling hard parts are in our hard parts category.

Install notes

• Follow the setup instructions that come with your gear set and spacer, and measure pinion depth with the spacer in place rather than guessing from the old shim pack.
• Revolution Gear and Axle's chart for the Ford 10.25 and 10.5 lists a 0.025 in starting pinion shim, 20-35 in-lb of pinion bearing preload, .006-.010 in backlash, 95 ft-lb on the ring gear bolts and 80 ft-lb on the caps.
• Backlash and carrier bearing preload are set with the threaded adjusters, so lock them with their retainers before the cover goes on.
• Fill with the gear oil and quantity Ford specifies for your truck, plus friction modifier if it has a Trac-Lok.

Pair the spacer with a 10.25 gear set such as the Yukon 10.25 3.73 gear set, and do the bearings while it is apart; the Koyo 10.25 master bearing kit and the Revolution 10.25/10.5 master install kit are the two to compare, and we can confirm which one matches your gear set and housing. A grooved yoke will chew through a new pinion seal, so check it and use the Yukon long-spline flange yoke if the seal surface is worn.

Which trucks need this spacer?

Trucks with a 2008-2010 Ford 10.5 Sterling rear housing that are getting a 10.25 ring and pinion set. Older housings and matching 10.5 gear sets do not need it.

Does it work on a 2011-and-later Super Duty?

No. Yukon lists it for 2008-2010 10.5 housings. 2011-up trucks use a different pinion with a 37-spline flange and take their own gear sets and kits.

How thick is the spacer?

Yukon lists it at 0.120 in thick. It is a single conversion spacer, not a full shim kit.

Do I still need a bearing kit?

Yes. The spacer only allows the 10.25 gears to fit the newer housing. Plan on new pinion and carrier bearings, a crush sleeve, seal and ring gear bolts for the gear swap.

What if my truck has a Dana rear instead of a Sterling?

Then this part does not apply. Some later F-250s use a Dana-built rear, so read the axle tag or door sticker axle code before ordering.