W ith any auto-motive repair job, whether you’re dealing with used or new compo-

nents, it’s critical to first clean those parts with solvent. Working with driveline ring & pinion gears is no exception. Let’s get right to it.

Using a fine file, remove any burrs on the rear of the ring gear and carrier mounting surface, then clean the sur-faces and housing to remove any metal particles, including any oil passages in the housing. Be sure to clean out any oil grooves adjacent to the carrier bearings. With axles removed, clean the axle tubes with solvent-soaked rags until they’re absolutely clean. All seal surfaces should be inspected for im-perfections. If necessary, polish seal surfaces with a fine-grit emery cloth and clean with solvent.

If you’re dealing with a used ring & pinion set, whether rebuilding an existing axle assembly or installing a used set of a different ratio, inspect the back face of the ring gear for flat-ness. A slight taper may have occurred during heat-treating. Any taper or un-evenness can be corrected by lapping the ring gear face on a flat glass plate with sandpaper or emery cloth.

Whether new or used, check the ring gear mounting surface for nicks or burrs and correct as needed to en-sure a flush mounting surface.

When setting up a differential ring & pinion, the critical adjustments required include pinion depth, pin-ion bearing preload, gear backlash and carrier bearing preload. Go slow and pay attention to details. Expect to perform an initial test fitting and adjustment prior to final setup. As noted by West Coast Differentials (www.differentials.com), pinion depth shims are placed either under the rear pinion race or on the pinion

shaft under the rear pinion bearing.During initial setup, try using the

original shim depth for your first at-tempt. The rear pinion bearing must be pressed on the pinion shaft and the pinion races must be tapped in-to the housing with a large punch so they seat evenly. Install the front bearing and carefully tap the pinion seal in place with a properly sized seal driver or an old race. West Coast Differentials notes that Ford 8- and 9-in., and GM 10.5- and 12.25-in. ring gears use a pilot bearing that must be tapped in, with a retainer for the Fords. Mount the ring gear to

30 October 2015

RING & PINION SETUP BASICS

The prospect of installing and adjusting driveline ring & pinion gears can be intimidating for shops that don’t routinely perform this task. Even if you farm this

work out to a specialist, you should understand what’s involved.

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has been established. Always use a new crush sleeve for fi nal assembly.

When installing a crush sleeve, slide the sleeve onto the pinion shaft and install the pinion through the rear of the housing. According to West Coast Differentials, the yoke usually must be tapped on while you apply pressure on the pinion gear head to hold it in place. Use an im-pact wrench or huge breaker bar to apply the torque necessary to crush the sleeve. Proceed very slowly so so as not to overload the bearings. The pinion preload will be zero until the bearings contact the races but will then increase very quickly. Again, use an inch-pound torque wrench to check the preload. If the pinion bearing preload exceeds the specifi ed allowable range, install another new crush sleeve and start over. If the design calls for a crush sleeve, it’s a good idea to keep a handful of these sleeves handy during test-fi tting.

If preload setting requires the use of shims instead of a crush sleeve,

fi rst carefully clean the shims to re-move any particles that may cause a false preload reading or cause the shim stack to change thickness over time as the vehicle is driven. Main-tain a clean surface on your work-bench while organizing shims to pre-vent contamination.

Slide the shim pack over the pinion shaft to the shelf. West Coast recom-mends using the original shims on the fi rst assembly, or adding .003 in. to the original preload shims to make up for the bearings settling into the housing.

Gradually tighten the pinion nut in increments to a fi nal value of approx-imately 250 ft.-lbs. Recheck preload with an inch-pound torque wrench as you go, between nut-tightening incre-ments, to avoid damaging the bear-ing. (Don’t immediately tighten to full value, and keep rechecking pre-load.) If the preload is too tight, re-move the pinion gear and add shims so the bearings will not be as tight against the races. If the preload is too loose, remove shims so that the bear-ings will be tighter against the races and increase the preload.

Once you’ve achieved the proper preload, lightly tap both ends of the pinion to seat the bearings, races and yoke. Once the pinion has been seat-ed, recheck the pinion preload with your inch-pound torque wrench.

Insuffi cient carrier bearing pre-load allows the carrier to move when under load; this can cause the back-

32 October 2015

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the carrier with a drop of red (high-strength) threadlocking compound on each bolt. Carrier bearings are pressed on the carrier and secured with green Loctite. Note that in Dana Spicer differentials, the carrier shims are located between the carrier and carrier bearings.

It’s important to note that pinion bearing preload is always measured in inch-pounds at the pinion nut, so a quality, calibrated inch-pound beam- or dial-type torque wrench is need-ed. Be sure to apply clean oil to the pinion nut washer surface during all assemblies and high-strength thread-locking compound (for example, red Loctite) on the pinion nut threads during the fi nal assembly (not during initial test fi tting).

Some designs feature a crush sleeve for setting pinion depth, while others require the use of preload shims. If the design calls for the use of a crush sleeve, it may be easier to ini-tially install the pinion without a crush sleeve until the correct pinion depth

On a ring gear, the outboard area is re-ferred to as the heel, while the inboard area is the toe. The drive side receives the push-force from the pinion gear. The shad-ed areas depict an ideal wear pattern.

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lash to open up. West Coast notes that carrier bearing preload is not specifically measured, but a good, tight fi t is important in all differential designs. Backlash is measured by mounting a dial indicator to the hous-ing with the plunger set perpendicu-lar to the ring gear teeth. While hold-ing the pinion yoke steady, rotate the ring gear back and forth. Backlash will generally change about .007 in. for each .010 in. the carrier is moved. To decrease the backlash, move the carrier closer to the pinion center-line; to increase the backlash, move the carrier away from the pinion cen-terline. Backlash may be adjusted by threaded adjusters or with the use of shims, depending on the design.

Typically, backlash for a street ap-plication will be in the .007- to .009-in. range. The backlash adjustment for GM and Dana applications is typically accomplished with the use of shims placed behind the carrier bearing cups.

Once the gears are initially in-stalled, paint the pinion gear teeth with a gear-marking compound or machinist’s dye to check gear-to-gear tooth contact patterns. Rotate the ring gear several times by hand and inspect the ring gear teeth. If the wit-ness pattern shows heavy on the “toe” (inboard area of the ring gear), sub-tract shims. If the pattern is heavy on the “heel” (outboard area of the ring gear teeth), add shims. Ideally, the contact pattern should be seen in the

middle area of the teeth. Resetting the pinion depth may be necessary as well.

If the carrier features a thread-ed screw adjuster design, first lube the adjuster threads with oil on both the housing and the adjusters. While holding the races on the bearings, place the carrier in the housing. In-stall the carrier caps according to the marks made during disassembly so the threads are seated evenly on the adjusters. Note that third-member differential designs require a 10- to 12-in. spanner wrench to tighten the adjusters. West Coast notes that Chrysler differential designs require an extension bar and special span-ner to access the adjusters through the axle tubes. Tighten both the left and right adjusters evenly by hand until they’re fairly tight. If the back-lash is excessive, tighten the left ad-juster until the backlash is correct; if the backlash is too tight, tighten the right adjuster until the backlash is correct. If necessary, loosen one adjuster and tighten the opposite ad-juster. Once the desired backlash has been achieved, both adjusters must be fully hand-tightened. The fi nal ad-justment requires tightening the left adjuster, since the ring gear is forced away from the pinion gear while un-der load.

Differentials that require shims may need them between the carri-er bearing races and the housing,

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Circle #20

33October 2015

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These are examples of the checking distance between the axle centerline and the pinion on typical GM and Chrysler applications (left) and on Ford 9-in. applications (right).

2.468

Place Shims Needed to Get to the Required Pinion Depth in These Locations

Place Shims Needed to Get to the Required Pinion Depth Between Bearing Support & Housing

CheckingDistance Checking

Distance

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or between the carrier bearing and the carrier case. Carrier bearing pre-load is established by the tightness

of the shims. The carrier should be shimmed tight enough that it must be tapped in with a plastic dead-blow

hammer. While holding the races on the bearings, and with outer shims on the races, start the carrier into the housing and tap it in with the ham-mer. Install the carrier caps accord-ing to the marks made during disas-sembly. Measure the backlash. If it’s excessive, move or add shims to the left side. If the backlash is too tight, move or add shims to the right side. If the carrier is too tight or too loose, remove or add shims as needed.

The pinion depth specification (measured from the pinion face to the axle centerline) should be marked

34 October 2015

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Circle #21 Circle #22

A new ring & pinion set can be damaged quickly—as this one was—if adjustments and/or lubrication aren’t correct.

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The ring & pinion gear contact wear patterns shown on the left indicate that the pinion was adjusted too deep. The patterns in the center indicate that the pinion was adjusted too shallow. Acceptable wear patterns are shown on the right. The ideal pattern is seen in the top two examples on the right.

Performance.indd 4 9/23/15 2:41 PM

This article can be found online at www.motormagazine.com.

on the face of the pinion and must be set, staying within .002 in. of the specifi cation. Depending on the style of the assembly, either a crush collar or shims can be used to adjust pin-ion depth. Once the pinion depth has been set, pinion preload must be applied while rotating the pinion. For used bearings, set preload at 15 in.-lbs.; with new bearings, set pre-load with 25 in.-lbs. Once preload has been set, install the pinion seal and the pinion locking nut (apply red Loctite high-strength locking com-pound or equivalent). With the pin-ion gear installed, position the ring gear and carrier into the housing and inspect gear backlash.

Never mix & match ring gears and pinion gears. These are made as sets, and gears are lapped as a set. Inspect each gear to verify that the serial numbers match.

Always apply a coat of gear oil on all bearings and grease on all seals

and seal surfaces just prior to instal-lation. Refer to the gear maker’s lu-bricant recommendation; generally, a synthetic 75W-140 gear lube should be correct. If the differential is a pos-

itraction/limited slip design, a friction modifi er will be required in addition to the gear lube. The amount of fric-tion modifi er can vary depending on the application, but generally some-where between 4 and 8 oz. should suffice. If a friction modifier is not added to the lube when required, driveline chatter may occur (as a re-sult of clutches sticking), possibly most notably in Reverse with the steering wheel turned.

For street operation, with gears sets of 3.73 or lower (3.73 or highernumerical ratio) it’s recommended to drive the vehicle for about 500 miles at varying speeds. Avoid constant cruising in one speed range.

Thanks to West Coast Differentials and Richmond Gear for their assis-tance with this article.

Inadequate lubrication resulted in a severe overheating condition, as evidenced by this example of a badly burned ring & pinion set.

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Circle #22

35October 2015

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Performance.indd 5 9/22/15 5:20 PM