Tech / Tech Articles

Gear Doctor: Quick Guide to Diagnosing Common Ring & Pinion Issues


What grinds your gears?

Is it prematurely worn or chipped teeth? Or an ominous clunking sound?

These symptoms can be signs of a fairly serious problem with your ring and pinion gears, so it’s time to consult with the doctor—the gear doctor. In this case, the gear doctor is the Summit Racing technical department, which helped us compile this quick guide to diagnosing common ring and pinion issues.

Before we get into the specific symptoms, it’s important to determine whether you’re using the proper gears for your vehicle. Here’s a breakdown of the three specific types and their intended purposes:

  • Street Gears (OEM type): These gear sets are designed for mild performance applications in which comfort is a factor. They are cut like an OEM gear to keep gear noise or whine to a minimum but are made from a higher grade alloy than OEM.
  • Performance Gears: These gears have teeth that are cut differently than the OEM version to make them stronger; however, they are often noisier than OEM.
  • Pro Gears: These gears are for drag racing only and cannot be used on a street vehicle. Produced by Richmond Gear, Pro Gears are made from a softer, more malleable alloy to resist breakage under harsh conditions.

Once you’ve determined that you’re using the proper gears for your application, you can start looking at other causes for premature wear or unusually noisy performance. According to Summit Racing, here are some of the most common problems and causes:

Problem: Gears make excessive noise.

Possible Cause #1: It’s possible this noise is just normal, depending on the gearing you have. Remember, numerically higher gear sets (3.73 or higher) are typically noisy by nature because they use a pinion gear with very few teeth and are cut differently than street gears.

Possible Cause #2: Excessive noise can also be caused by improper spacing. Because aftermarket gears can require different spacing than the OEM set, you can’t use the old shim spacing. To ensure proper installation, you’ll need to determine the proper spacing by using a pinion depth setting too .

Possible Cause #3: If spacing is correct, it’s possible that improper tooth contact could be to blame for excessive noise. After the gears are installed using a pinion depth setting tool, you should always check the wear pattern using a marking compound. You should see the wear pattern closer to the toe of the tooth with most gear sets.


Problem: Teeth on the gear set are excessively worn, chipped, or broken.

Possible Cause #1: As mentioned above, aftermarket gears can require different spacing than the OEM set, so you can’t use the old shim spacing. Again, you’ll need to determine the proper spacing by using a pinion depth setting tool to ensure proper installation. Improper gear spacing will lead to wear and damage to your gear set.

Possible Cause #2: Worn carrier or pinion bearings can create excessive play between the gears and produce an uneven wear pattern or chipping teeth. Check for worn bearings and replace as necessary.

Possible Cause #3: Incorrect backlash can lead to damaged gear teeth. The backlash setting, which affects how much fluid gets between the teeth of the gear set, should be set between .006 and .009 inches. If this setting is not correct, it may cause overheating or damage to the gears.

Possible Cause #4: Improper break-in will lead to premature wear. Make sure to always follow the break-in procedure outlined in the manufacturer’s instructions. As a rule of thumb, new gear sets should used lightly for the first 20 miles and then allowed to cool down. If driven too hard, the gears will wear early and cause excessive noise.


Problem: Gears “clunk” from a dead stop.

Possible Cause #1: Does the “clunk” sound only occur when your vehicle starts to move? In this case, the gears typically aren’t the problem at all. Instead, it’s often a loose pinion yoke, bad U-joint, or worn transmission making the noise.

Possible Cause #2: A second possible cause is the crush sleeve. If the crush sleeve is not crushed properly, the pinion yoke will be loose and the pinion bearings will not be seated correctly. Keep in mind, it typically takes 300-400 ft.-lbs. to effectively crush the crush sleeve.

Problem: Gears have been getting louder with time.

Possible Cause #1: Improper break-in can cause gears to become louder with repeated use. As we outlined above, new gear sets should used lightly for the first 20 miles and then allowed to cool down. If driven too hard, the gears will wear early and become increasingly noisy.



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  1. 1998 gmc half ton 4×4 z71. Started making like a vibrating noise a few weeks ago, increasing noise. Now it makes a clanking noise when deceleration. Drive shaft had play, now has none what so ever. U-joints don’t look bad, but I’m going to install new ones anyways. The rear end that it has now is a ten bolt. Is it possible the carrier bearing is bad.

  2. Have a 2001 chevy Blazer Changed the bearings on axle no have a thumping noise coming from the rear end can you tell me what i should check ??

    • OnAllCylinders says:

      This seems like a pretty straight forward job until you pull the C-clips to get the axles out and the spider gears fall out of the case. Generally when this happens the washers on the back of the small spiders will come off and roll across the floor. Reassembly without these will still allow normal operation of the vehicle but allows too much clearance inside the carrier and causes a clunk.
      Another thing worth a look is the internal E-brake shoes. Many time the backing plates are rusted badly and the retaining pins come loose and the shoe moves around and can cause a noise. Good luck!

  3. Ronnie Faulkner says:

    I have installed a Detroit locker in a 1952 M135 duce and a half rear diff. I set backlash to spec ~ 0.007, then performed a gear pattern with marking compound. The patter was off and running in the center of the toe. I increased the backlash ~ 0.020 to get a good gear pattern. Seems I will not be able to achieve both spec backlash and gear pattern. With the positioning of the adjuster nut locking clip there is nothing in-between. Should I go with the 0.020 backlash for gear pattern or with the spec backlash?

  4. LIONEL CULLEN says:

    On my last 10,000 service on my Ford Fairlane AU 2 Ghia, 2002, which has done 333.480 km has been reported by the mechanic that the REAR DIFF PINION BEARING IS NOISY. What action should I take & if I continued to drive the car, is there a problem?

  5. Joe O’Donnell says:

    Dear David,

    I recently purchased a 1951 Chevy Deluxe. When in gear, during deceleration, it really whines. Put in the clutch and whine goes away. We pulled the housing off the rear end and noticed very clean oil. It had been serviced recently obviously. However, the heels of the ring gear has little chips and very little marks at the tops of the tooth heel. Almost like it’s been getting chewed up by something.

    Mechanic said we’ll just file em down. He thinks we need to replace the differential because the pin has too much play. I have this feeling the pinion is chewing the teeth of the ring for some reason. They serviced the driveline before I bought it with new bushings etc. I have this feeling they did not adjust the pinion correctly. Few mechanics around here seem to understand what’s going on. What do you think? Tooth heals being chipped off is not a good sign.

  6. Richard Mulholland says:

    Have a aam11.5 rear end put 4.56 gear in it the drive is quiet and so is the coast until it get around 65 down to 55 it whines but no noise after that.its a yukon gear i thought it might be a loose pinion nut but preload is correct ant nut hasn’t backed off.

  7. Pingback: What’s That Noise in My Differential? -

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