Car Makes Noise When Reversing? Diagnose & Fix Engine and Transmission Mounts

Steps to diagnose engine and transmission mounts on a car that makes a knocking noise when reversing

1. Look for Signs of a Fluid Leak

   Engine and transmission mounts can fail for different reasons. An oil spill could be leaking onto the mount, causing swelling and eventual damage like cracking or the rubber separating from the mount. If the mount loosens, you may hear clunking and feel vibration.
   
   
   
   

2. Check the Engine and Transmission Mounts for Dry Rotting, Cracking, or Separation

   Engine and transmission mounts can dry-rot, crack, and separate from use over time. A damaged or worn mount can strain the remaining mounts and wear them out faster than usual.
   
   

3. Listen for a Clunking or Knocking Noise When Driving

   If you hear a clunking noise when driving or reversing, that’s a sign of one or more mounts being worn. Feeling a vibration from the front while driving is a typical sign of a worn engine mount.
   
   

4. Feel for a Vibration When Driving

   The mount has lost strength, there’s metal-on-metal contact, and vibration from the driveline is transferred to the interior of the passenger compartment. These signs mean it’s time to inspect the engine and transmission mounts.
   
   

5. Feel the Mounts for Looseness with a Pry Bar

   You can pry between safe areas with a pry bar, being careful not to break any covers or sensors.
   
   

6. Perform a Brake Stand and Watch the Transmission and Engine for Excessive Movement

   You can also have an assistant help you inspect the engine and transmission mounts by doing a brake stand. Don’t stand in front of or behind the vehicle while doing this.
   
   A brake stand is when you press the brake to keep the car in place, and then press the gas. Have a helper put the e-brake on and press and hold down brake pedal. Then put the transmission in drive or reverse and step on gas a few times.
   
   As the helper is doing this, check the transmission or engine for excessive movement. For example, if the engine flops around a lot and hits against a section like the firewall or body, there’s a problem with one of the mounts. Generally, excessive forward and backward movements indicates there’s a problem with the front or back mount, and side-to-side movement indicates there’s a problem with the side mounts.