[Gilles]

Since you have vibration on the front axle while turning left, I would bet on the right side wheel bearing..

You can check the bearings by raising the front wheels off the floor and rotate the wheel by hand and also checking for play between 6 and 12 and also between 3 and 9.

PS: If the vibration is on the rear axle, then check the same way. Please note that a bad bearing also 'rumbles' when you load it, and you can also check it going downhill with the engine off, veering to the right, then to the left, a bad bearing you will hear it rumble