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There’s a lot of potential for vibration in a car. There are many sources that cause vibration, and if a single component designed to dampen that fails, you’ll feel it. Motor mounts, transmission mounts, suspension bushings…these are just a few of the things that are designed to minimize vibration and make driving more comfortable while prolonging the life of your vehicle overall. If your car vibrates when going up a hill, that actually narrows the possibilities down somewhat.
There are a couple of different potential issues here, and they’re not part of the same system. One involves the drive shaft in a rear-wheel or all-wheel drive vehicle. Drive shafts are essentially long, metal cylinders that attach the transmission or transfer case to the rear differential. The driveshaft turns with the transmission, and in turn it drives the gears in the differential, which turn the rear axles to spin the wheels.
In a front-wheel drive car, there is no differential, but you do have CV axles that connect from the transmission to both wheel hubs. These spin with the transmission and turn the front wheels, giving your car the ability to move.
Problems with either the CV axles or the driveshaft will definitely cause vibrations going up a hill, and sometimes under very hard acceleration on flat surfaces or gentle inclines.
Damaged CV Axles: If you have a front-wheel drive vehicle, one of the first things to suspect is damage to the CV axles. If an axle is even slightly bent, it will create a vibration that’s much more noticeable under heavy loading, such as driving up a hill. CV axles can be bent by many things, including impacts, in accidents, and even by improper tying down when being loaded on a flatbed.
Damaged CV Joints: Each CV axles has two CV joints, one at either end. CV joints allow the axles to flex when going over dips and bumps, without losing traction and without damaging the axle. If a CV joint is failing, or beginning to fail, then you may experience a vibration when driving up a hill.
Failing U-Joint: In a rear-wheel drive, the driveshaft is equipped with one or more U-joints (universal joints). Essentially, they allow the driveshaft to flex under heavy loads while still transmitting power from the transmission to the rear differential. Over time, U-joints become lose, causing excess vibration, particularly under a heavy load like driving up a hill.
Low or Dirty Differential Fluid: Your differential contains a series of gears and other internal components that need lubrication. This is provided by differential fluid (sometimes called gear dope). If the fluid is low, you can expect to see a vibration under heavy loading. This is also possible if the fluid hasn’t been changed in some time.
A top-rated mobile mechanic will come to your home or office and inspect your vehicle, including the CV axles and the driveshaft U-joints (depending on whether you have a front or rear-wheel drive vehicle). The mechanic will then provide a detailed inspection report that includes the scope and cost of the necessary repairs.
The mechanic will need to test drive the vehicle to duplicate the vibration when driving up a hill. The mechanic will also check the U-joints if you have a rear-wheel drive, and the CV axles/joints if you have a front wheel drive. Additional diagnostics may also be required.
Experiencing a vibration when driving up a hill is a sign that something is wrong with your car’s driveline. It could be with the CV axles, CV joints or driveshaft U-joints, or it could be from something else. Regardless, it’s important to have the problem professionally diagnosed and repaired before serious damage occurs (a bent CV axle can break, leaving you stranded, or a loose U-joint can damage the driveshaft). One of our professional mechanics can diagnose and repair the problem correctly.