McCullough NAPA Auto Care

Dear valued customers:  Please do not park in the driveway as it is shared by all businesses in the complex.  Please make sure that you park in the McCullough parking lot.  If you need help with parking, please let us know.  We will be glad to assist.  Thanks for your cooperation!


Mon-Fri: 7AM – 6PM
Saturday & Sunday: Closed

Serving Metro Atlanta Since 1969

A damaged differential can negatively impact your safety on the road. This article outlines the function a differential has on your wheels and how you can detect the symptoms of a bad differential. 

What Does a Differential Do?

To understand the differential, we begin with the transmission. Your car’s transmission sends power to the driven wheels. If these wheels were forced to spin at the same speed, it would strain the axle and hinder your car’s turning abilities. This is where the differential comes into action, allowing each vehicle’s driven wheel to spin at a different speed while turning. 

Think of how a differential works by thinking of a high school track. You’ll notice that the starting lines for the outside lanes are ahead of the starting lines for the inside lanes. This compensates for the longer length of the outside lanes due to the track’s circumference.  Staggering the lines allows each runner to have the same distance to run overall.

The differential compensates for the difference in speeds between the inside and outside wheels during a turn. The wheels have to travel together, but they travel slightly different distances. The differential works to adjust wheel speed as needed to assist with turning.

Symptoms of a Bad Differential

A bad differential can compromise your vehicle’s turning ability and cause your wheels to lock up. Differential damage can spread to other components of your car. Look for these symptoms of differential damage to determine if you need repair.

  • Loose pinion-bearing preload – Listen for a high-pitched howling noise as you decelerate gears. 
  • Broken pinion-gear tooth – Listen for loud clicking or clunking sounds when driving.
  • Worn pinion bearings – Listen for whirring noises when driving at various speeds. 
  • Bad wheel bearings – Listen for rumbling sounds as you turn. Test this in an empty parking lot to be sure.
  • Worn carrier bearings – Listen for a whirring or rumbling sound when driving over 20mph. The noise may change pitch when turning.
  • Worn U-joints – Does your car shake excessively, especially while accelerating? Your U-joints may be worn out.
  • Broken cornering gears – Listen for banging, clunking, or clicking sounds while you turn a corner. Test this in an empty parking lot to be sure.
  • Worn transfer case – Listen for a clunking or clicking sound when you press or release the throttle.
  • Out-of-balance driveshaft – Feel for heavy vibrations while accelerating.
  • Insufficient lubrication – Your car’s differential needs sufficient lubrication to function correctly. Low gear or differential oil levels can cause a clunking or banging sound when cornering.

Schedule Differential Service with McCullough NAPA Auto Care

McCullough NAPA is a family-owned auto care center with 50+ years of experience. Our technicians are ASE Certified and equipped with the technology to diagnose your differential for damage and make repairs if needed. Allowing common differential problems to compound on each other can escalate into a major repair quickly. 

Schedule your appointment online for a differential inspection or service.