Front end vibrations at high speeds or in 4 wheel drive

[brentandlorie]

1998 Mercury Mountaineer AWD....v8...4 speed automatic.

The trucks front end vibrates horribly when the placed into 4 hi from auto.

Also bad vibrations at 65+.
Tires are matching and balanced.
tie rods look good, ball joints good.

drives good otherwise.
any help would be appreciated.

brent

 

[jlsparky7]

Few other things to check.

Wheel bearings
U joints
Driveshaft bent? (needs balancing?)