If you feel a heavy and extensive vibration coming through the steering column, make sure you check the following:

Wheel out of balance

An unbalanced wheel or loose wheel can cause vibration throughout the vehicle. 

Check the front and rear rims and tyres for damage. Replace if necessary.

Possible built up of mud can occur in and and around of rims and tyres. Remove build and and clean affected areas.

Rims and tyres may be out of balance.

Low or uneven tyre wear

Check the tread on each tyre. If they are worn, replace with new tyres. 

If one side of the vehicle has more worn tyres than the other side, 

Replace the worn tyre/s and carry out a wheel alignment.

Damaged or worn steering components

Check all the steering components and linkages. 

If any are worn or damaged, replace.          

Damaged or worn shock

Check for free play in spherical bearings at the top and bottom of the shock absorber.

If they are worn or damaged, replace.