If you are hearing a thumping sound from the rear and under the car when driving you are not alone. This is one of the most common noises coming from under a vehicle. Fortunately in this article, we will focus on the actual cause of this noise and how to eliminate it.
It should be noted that I will be referring to a “thump” sound from anything, such as a subframe, all-track, or a driveshaft breaking. The reason for this stems from the fact that most of these noises have either come from the subframe or driveshaft area. Let’s dive in
What Causes Thumping Sound on the Car Rear?
Worn Ball Joints:
When ball joints go bad it is usually accompanied by a popping or cracking sound. Another symptom of worn ball joints is a clunk or rattle sound when going over bumps or hitting off of curbs.
If your ball joints are worn you are going to want to replace them as soon as possible. Not only do they make horrible noises, but they can be dangerous as well if they start to fail while driving down the highway.
It is recommended that you have these parts tested and replaced anytime your vehicle hits the 80000-150,000 mile range.
Bad Control Arm bushings:
I want to start by saying that these types of noises can come from a number of different places. The control arm bushing is the bushing in between the control arm and the ball joint.
Control arms are a major part of your vehicle and they are designed to take all of the wear from driving. Unfortunately, this can lead to a rattle or rattling noise coming from the inside of your vehicle. This will be accompanied by a bad vibration or shuddering feeling when going over bumps or hitting off curbs.
Failing Engine Mounts:
As your vehicle accelerates, the weight of the engine and transmission is being transferred to the mount. The mount then transfers this weight to the subframe and control arm. It is not uncommon for these mounts to become worn out or even crack and split.
This will cause unwanted vibrations in your vehicle that you may not notice until they start to get bad. A combination of a bad mount paired with a worn ball joint will cause you to hear this type of noise from under your vehicle.
Loose Exhaust System:
If you are hearing this type of noise coming from the back of your vehicle, it is possible that the exhaust system is starting to break down. A common indicator of a bad exhaust system is a losing or worn-out heat shield or catalytic converter.
This will usually cause you to hear a loud exhaust leak when your vehicle reaches operating temperature. If you have an engine light come on or if you are smelling exhaust fumes in your cabin, you should bring your vehicle in for service.
Bad Wheel Bearings:
As your vehicle accelerates and the suspension in your vehicle transfers power to the wheels, you will start to hear a rattle or vibration coming from either the front or rear of your vehicle.
The wheel bearing lives in a sealed environment and as they wear down they will start to vibrate. What is happening right now is that you are not hearing it because it’s something that happens quietly under your car. This can be extremely dangerous as this vibration will cause your tires to slip on the road and can end up causing a disastrous accident.
Uneven/unbalanced Tires:
If your tires are uneven in any way, you could be causing a rattle or vibration under the car. Tires rarely wear down evenly, so you will want to visually inspect each tire and check for uneven wear.
It is especially important that you understand how to properly check for even wear if your vehicle is equipped with staggered applications. For example, when checking for rear axle tire wear; you want to be sure that both tires have the same amount of wear on the inside and outside tread of the tire.
What to do when you hear thumping sounds on your vehicle?
Once you are able to pinpoint the exact source of your thumping sound, you will want to have it inspected and repairs are done.
If the noise is coming from a subframe or driveshaft area, you are going to want to have it replaced as soon as possible. The best way to go about is by taking the vehicle to the nearest, best repair facility.
This will give you the most reliable and accurate diagnosis as to what exactly is causing your vehicle to make that awful noise.
Final Thoughts
The thumping sound coming from your rear end is never a good sound to hear. This can be a sign that there are some serious problems with the suspension, so it’s critical that you diagnose the sound correctly and have it repaired as soon as possible before it gets worse.
Robert Anderson is a world class motorhead who rebuilt his first carb at age 10, his first engine at age 15, and completed his first full hotrod build when he was just 18! Previously, he has ran a part warehouse, delivered pizzas, and managed the service department for a $20 million/year revenue dealership. Robert knows cars like few others and he is passionate about sharing his knowledge.