Yukon Gear Pinion Depth Shims For Ford 9in w/ 7/16in Studs

Regearing a Ford 9 inch and the contact pattern keeps landing on the toe and the face instead of the middle of the tooth? On this axle the answer is shims under the pinion support, and this Yukon Gear and Axle SK F9-7/16 set is the one for third members whose pinion support bolts down on 7/16 in. studs. It covers the 9 inch rear ends under 1957-1986 Ford trucks and cars and the street rods, drag cars and rock crawlers that have carried a 9 inch ever since.

What pinion depth shims do in a Ford 9 inch

Pinion depth is the distance from the pinion head to the centerline of the ring gear. Every ring and pinion set is lapped to run at one depth, and a new set rarely matches the depth the old one ran at. In a Ford 9 inch the pinion, its two tapered bearings and the straddle bearing pocket all live in one cast pinion support, sometimes called the pinion cartridge or retainer. That support is bolted into the nose of the third member on studs, and the shim stack goes between the two. Adding thickness backs the whole pinion out of the ring gear; removing it pulls the pinion in. Because the bearings never come off the pinion to make a change, the 9 inch is one of the easier axles to set up, provided you have enough shim sizes on the bench.

Signs your 9 inch needs a depth correction

• A new ring and pinion that howls on the gas or on coast after the first drive, with backlash already checked.
• A marking compound pattern that sits high on the drive side face or deep on the flank instead of centered.
• Pitting or scuffing on a gear set that was installed with the old shim reused, common on high horsepower builds where gear wear shows up first.
• Gear oil that comes out dark and smells burnt after a short break-in.

A steady growl on an old, original 9 inch is a different problem: pinion support bearings and carrier bearings wear out first on this axle. That calls for a bearing kit, and depth gets checked again when the new bearings go in.

How to confirm the depth is off

Bolt the pinion support down with your current stack and set backlash inside the gear maker's range. Paint about a third of the ring gear with marking compound and turn the pinion both ways with some drag on the ring gear. Read the drive side first. A pattern pushed toward the top land means more pinion depth is needed, so take shim out. A pattern pushed down toward the root means the pinion is too deep, so add shim. Measure each shim you use with a micrometer, write the stack down, and change one thing at a time.

Fitment

The SK F9-7/16 shims are cut for Ford 9 inch housings with 7/16 in. pinion support studs. Not every 9 inch uses that size, and a shim with the wrong hole size will not seat on the case. Measure a stud, or check the bolt holes in your existing shim, before ordering. If the third member has been changed to an aftermarket case or support, test fit a shim before final assembly. Send us the housing casting number or a photo of the pinion support if you want a second check. More parts for this axle are in our hard parts category.

Install notes

• These are shims only. If the pinion bearings or seal are worn, start with a Yukon Ford 9 inch master overhaul kit with crush sleeve eliminator or the USA Standard 9 inch master overhaul kit for LM501310 carrier bearings.
• Clean the case nose and support flange to bare metal. Any burr or gasket residue acts like an extra shim.
• Use as few shims as possible to hit your target, and run the support nuts down to full torque every time you check a pattern.
• If you are changing ratio at the same time, a Ford 9 inch 3.50 ring and pinion set is a common highway-friendly choice.
• Refill with 75W-90 or 85W-140 gear oil, add friction modifier only if your limited slip calls for it, and go easy for the first few hundred miles while the new gears break in. Worn outer axle bearings are the other common 9 inch noise, and the tapered axle bearing and seal kit fits housings with 3.150 in. OD bearings.

How do I tell if my 9 inch uses 7/16 in. pinion support studs?

Measure the diameter of one of the studs that the pinion support slides over, or the bolt holes in the old shim. These shims are made for 7/16 in. studs; housings with a smaller stud need a different shim set.

Do I have to press the pinion bearings off to change shims?

No. On a Ford 9 inch the shims go between the pinion support and the third member case, so you pull the support assembly, change the stack and bolt it back on.

Pattern is on the top of the tooth. Add or remove shims?

Remove shim. A pattern high on the face means the pinion needs to move closer to the ring gear centerline. A pattern deep on the flank means add shim.

Is a bearing or seal included?

No, this is a shim set only. Pair it with a Ford 9 inch overhaul or install kit if the bearings, seal or crush sleeve need replacing.

Can I reuse my old shim with new gears?

Use it as a starting point only. Every gear set is lapped for its own depth, so always check the pattern with marking compound before final assembly.