Toyota Sienna Car vibrates going uphill Inspection at your home or office.

Common reasons for this to happen:

• 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.