1999 Jeep Grand cherokee, can't steer

should be clips along the brake hose it clips in to

Vibration from about 40-60 mph is usually attributed to wheel balancing, but the onset when you hit a bump seems to indicate play in the steering linkages (tie rods etc) or suspension members and stabiliser bar rubbers but you had that all checked out, that brings us back to the wheel balancing.

Check your ball joints. also, if the tires are somewhat worn many times they won't have enough rotating mass to overcome side harmonics and can shake but most oftern the joints are worn. No play is acceptable there.

I can't say for sure without actually checking myselft but it sounds like one of four possiblilities, ball joints, tie rod ends or sabilizer bar ends or shocks.
To check the tie rod ends put the jeep on jack stands or a hoist, with the steering wheel locked try to turn the wheels back and forth and look for movement in the joints of the linkages.
To check the ball joints, while the jeep is up in the air grasp the top and bottom of the wheel and try tipping the wheel in and out, checking for movement in the ball joints.
Lower the Jeep back to the ground. Continue the tests by having a big friend or family member bounce the Jeep while you listen for and look for movement in the ball joints, stabilizer bar ends and along the linkage and abnormal movement in the shocks.

A steering vibration at high speeds is usually a result of front tire imbalance. A loose or worn front suspension or steering component can sometimes cause a vibration as well. You should check over all the joints (ie: tie rods, ball joints, track bar etc) and if that checks out have the front tires balanced.

check rear bushings, panhard bar etc. alighnment?

Problem may not be at the wheel but maybe something going on with the steering linkage, tie rods, or suspension part.

A very good possibility is a bad trac bar in the front-end, also how old is the front steering damper?

having off balance wheels will cause this. or bent wheels

Check your tie rods and the drag link bar which controls the steering. Have someone turn the steering wheel back and forth while you are underneath and you should be able to pinpoint the noise location.   I had the same problem on my 2001.  Replaced the lower tie-rod ends and also the ones on both sides of the drag link. This solved the problem.  Whether you do this job yourself or not, you will definately also need an alignment upon completion.