Chasing down car vibrations that only occur when you are driving can be challenging as most often you can not replicate them when stopped. This week we are dealing with a vehicle that has intermittent vibrations which are mainly felt when pressing the accelerator.
The vibrations in this case feel more like driving over a shoulder rumble strip. The problem is that they are not constant. In our situation, the issue is failed engine mounts, but cabin vibrations can be caused by various other issues that are worth inspecting.
Bad Engine Mounts
One of the most common causes of vibrations felt inside a car is the failure of engine mounts. While engine mounts typically cause vibrations when the car is parked, depending on the engine setup and how they have failed, a faulty mount can also cause the cabin to vibrate while driving. Engine mount failure usually results in constant vibration, but if only one mount has failed, it can cause vibrations only under load.
The transmission mount, like the one depicted in this scenario, can result in engine vibrations. In vehicles with AWD, 4WD, or RWD, the transmission mount is typically a rubber mount that may initially appear undamaged. If you are experiencing an unidentified vibration, the transmission mount could very well be the culprit, and it might be more cost-effective to simply replace it.
Driveshafts can also cause car vibrations. Balancing them is necessary to prevent this issue. Unbalanced driveshafts may cause vibrations only at specific speeds, usually at 40mph, 50mph, or 60mph. These vibrations tend to disappear at higher or lower speeds.
Worn CV Joints
A worn CV joint can cause vibrations while driving. One way to test the CV joints is to go to an open parking lot. Turn the steering wheel all the way to the left while you are stopped. Then accelerate relatively quickly. As you start to move in a circle from a standstill, you should hear the CV joint making a clicking noise. Repeat the procedure, but this time make a circle while the steering wheel is turned fully to the right.
Cars with independent rear suspension may also have rear CV joints. These do not produce noise when you turn in a circle, unlike the front CV joints. The most effective approach is to examine the CV joint and check for any cracks or grease leakage. The issue with rear CV joints is that they can still experience internal failure, even if the protective boot remains intact and shows no visible damage.
Guibo Flex Disc
A Guibo flex disc, also known as a flex coupler or flex joint, is a crucial component in the drivetrain of many vehicles, typically found in the connection between the transmission and the driveshaft. It consists of flexible rubber or elastomeric material sandwiched between two metal plates. While it’s designed to absorb and dampen drivetrain vibrations, it can become a source of vibration itself when it deteriorates or fails.
As the Guibo flex disc ages or sustains damage, the rubber or elastomeric material can degrade, crack, or develop excessive play. When this happens, it loses its ability to effectively absorb and dampen vibrations. As a result, any imbalance or misalignment in the drivetrain, such as worn U-joints, driveshaft imbalances, or engine/transmission misalignment, can transmit excessive vibrations through the weakened Guibo flex disc. These vibrations then propagate throughout the vehicle, causing noticeable shakes or vibrations when driving, especially during acceleration or at specific speeds. In such cases, replacing the worn or damaged Guibo flex disc is essential to restore smooth and vibration-free operation of the drivetrain.
Exhaust Pipe / Catalytic Converter / Muffler
A damaged exhaust bracket or a bent exhaust that has been dented and is now touching the car’s frame can also result in car vibrations. Typically, these exhaust vibrations not only cause vibrations in the cabin but can also produce loud noises. Conducting a visual inspection of the exhaust and ensuring it does not make contact with the frame should be easily noticeable once the car is lifted on a jack.
Chaings down car vibrations when driving especailly at high speed over 40mph or 60mph can be tricky and require expertise and a good mechanic. Here are some things you should check:
Common Causes of Cabin Vibrations While Driving:
Wheel and Tire Issues:
- Tire imbalance
- Wheel damage or bent rims
- Uneven tire wear
- Warped brake rotors
- Stuck brake caliper
Suspension and Steering:
- Worn shocks or struts
- Worn suspension bushings
- Misaligned wheels
Driveshaft and U-Joints:
- Worn or damaged universal joints (U-joints)
- Imbalanced driveshaft
- Engine misfires
- Faulty engine mounts
- Exhaust system problems
Less Common Causes of Cabin Vibrations While Driving:
- Worn transmission mounts
- Transmission issues (e.g., slipping clutch)
Axle and Differential Issues:
- Damaged or bent axle shafts
- Differential problems
- Worn or damaged drive belts, such as serpentine belts
- Worn or damaged wheel bearings
- Loose or damaged exhaust components
Other Drivetrain Components:
- Damaged or deteriorated Guibo flex disc (driveshaft coupling)
- Worn or imbalanced CV joints (for front-wheel-drive and all-wheel-drive vehicles)
Engine Performance Issues:
- Vacuum leaks
- Ignition system problems
Identifying vibrations in a car while driving can be challenging due to the various potential sources. To swiftly and accurately diagnose the issue, it’s advisable to rely on an experienced mechanic. A seasoned mechanic with prior knowledge of similar problems can often pinpoint the cause within minutes during a test drive. Conversely, a mechanic unfamiliar with the issue might spend an extended time experimenting with diagnostics, increasing the risk of misdiagnosis and added expenses. Expertise matters when it comes to efficiently resolving complex vibration problems in vehicles.
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