Ford 9 Inch Pinion Depth Shim Kit, 7/16 in. Studs

If you are setting up new gears in a Ford 9 inch third member and the pattern will not center, the fix is almost always pinion depth, and on a 9 inch that means changing the shims under the pinion support. This Yukon SK F9-7/16 kit is an assortment of pinion depth shims cut for 9 inch cases whose pinion support bolts on with 7/16 in. studs. It is the part builders of 1957-1986 Ford trucks and cars, street rods, drag cars and off-road 9 inch housings reach for when the one or two shims that came in a bearing kit are not enough to reach the right depth.

What the pinion depth shims do in a Ford 9 inch

The Ford 9 inch is a drop-out design: the ring gear, carrier and pinion all live in a removable third member, and the pinion and its bearings ride in a separate pinion support (the bearing retainer) that bolts into the nose of that third member. Most axles set pinion depth with a shim behind the inner pinion bearing race, which means pressing bearings on and off every time you test. The 9 inch is different. Its depth shims sit between the face of the pinion support and the third member housing, so the whole pinion assembly moves fore and aft as a unit when you change the stack. A thicker stack pulls the pinion back, away from the ring gear centerline. A thinner stack moves it in, deeper into mesh. Yukon describes these shims as precision machined for the individual application, with the hole pattern matched to the 7/16 in. stud support.

Symptoms that point to wrong pinion depth

• A whine on a fresh gear install that is loud on acceleration or on deceleration, but not both, which usually means the contact pattern is sitting off the center of the tooth.
• A pattern that runs onto the tooth face (top land) or down onto the flank (root) even after backlash is in spec.
• Chipped or scuffed teeth on a ring and pinion that was installed without a pattern check, especially on high-horsepower 9 inch builds, where gear wear is a known failure.
• Heat and gear oil that darkens quickly after a regear.

Growl that rises with road speed on an older, untouched 9 inch is more often worn pinion support or carrier bearings than depth. In that case you need bearings first, and these shims only help with the setup that follows.

How to confirm you need more shims

Set backlash first, then paint several ring gear teeth with marking compound and roll the gears both directions under light drag. Contact crowding toward the face of the pinion tooth means the pinion is too far out, so remove shim from under the support. Contact crowding toward the flank means the pinion is too deep, so add shim. Change one variable at a time, torque the support nuts down each time you check, and measure your actual stack with a micrometer instead of trusting the stamped size. Our Ford 9 inch ring and pinion bearing install kit covers the bearings and seal for the same job, and the Ford 9 inch problems and rebuild cost guide walks through the full overhaul.

Fitment

This kit fits Ford 9 inch third members that use 7/16 in. pinion support studs. Not every 9 inch case does. Some supports use a smaller stud and take a different shim with a different hole size, so measure a stud or a support bolt hole before you order. Aftermarket nodular cases and Daytona style supports should also be checked against the shim you have in hand before final assembly. If you are not sure what you have, send us the casting number from the third member and a photo of the pinion support and we will confirm it. You can browse more 9 inch setup parts in our hard parts category.

Install notes

• Clean the support flange and the case face completely. A burr or old gasket material under the shim stack changes depth just as much as a shim does.
• Stack the fewest shims that reach your target. Fewer layers seat flatter and hold depth better.
• Torque the pinion support nuts evenly in a cross pattern every time you check a pattern, or the reading is meaningless.
• Once depth is right, set final backlash, recheck the pattern, and fill with 75W-90 or 85W-140 gear oil to suit the build.
• If you are installing new gears, a complete Ford 9 inch installation kit with solid spacer or a Ford 9 inch master overhaul kit handles the bearings, seal and hardware, and this shim assortment covers the depth correction those kits leave short.

Builders who set up 9 inch gears regularly keep one of these in the drawer, because the depth change a gear swap needs is hard to predict until the first pattern is on the teeth.

Will this shim kit fit every Ford 9 inch?

No. It is cut for third members whose pinion support uses 7/16 in. studs. Some 9 inch cases use a smaller stud and need a different shim, so measure a stud or the support bolt holes before ordering, or send us the case casting number.

Where do the shims go on a 9 inch?

Between the pinion support (the bearing retainer) and the third member housing. You do not need to press the pinion bearings off to change depth, you pull the support assembly, change the stack and bolt it back in.

Do I add or remove shims if the pattern is on the face of the tooth?

A pattern crowding the face means the pinion is too far out of mesh, so remove shim under the support. A pattern crowding the flank means it is too deep, so add shim. Set backlash first and recheck after every change.

Does this kit include bearings or a pinion seal?

No, it is shims only. Pair it with a Ford 9 inch bearing install kit or master overhaul kit if you are replacing bearings, the seal or the crush sleeve.

What gear oil should I use after setup?

Ford 9 inch housings typically run 75W-90 or 85W-140 gear oil. Use the weight your gear maker and limited slip or locker manufacturer call for, and add friction modifier only if your carrier requires it.