Hello i have a problem when turning full left. It starts knocking and it kinda tries to "jump" and it feels like its gonna fail apart any second . All this coming front the left front wheel.

Also another problem i have is when driving above 50mph it starts shacking and knocking...thought i may be u joints, replaced but that didnt help. Could it be a drive shaft or yoke?

 

Have you checked ball joints including rod ends on the steering?

As for the over 50mph, have you had your wheels balanced recently, tyres changed without balancing or hit a curb? Without getting the wheels checked, you could swap the front with the back and see if it changes. If it does change, it could get better or worse depending on how the rear wheels are but a change would show that you've moved the issue.

I had an unbalanced wheel on the front and when I hit 55, it vibrated so badly I had to stop. Luckily I have my spare so swapped it out and got the bad wheel balanced the following Monday.

 

I havent yet checked the RE nor the BJ, gonna do that tomorrow.

For the other thing...
New tires 4 weeks ago, 235 75 15 BFG KO2 balanced
Wheels balanced 3 weeks ago.

Issue was there before the tire change.

 

The only other thing I can think of would be bearings or physical damage to the knuckle or hub. Let us know how the joints check out.

 

Also check for any cracks or rusting out of the control arm brackets, the control arm bushings (they shouldn't have put tires on it if the bushings were bad.. but some shops don't give a f) and that the sway bar bushings are in good shape at the ends as well as where the bar mounts to the frame.

 

Jumping, crow-hopping, thunking, and binding while in a full lock turn is almost always front axle u-joints. They don't like being at full lock in general, but as they wear out the condition will get worse. This problem will not be related to ball joints, tie rods, or control arms.

Shaking and knocking above 50 is going to require a little more information. If it only happens when "under load" (torque applied/accelerating) but smooths out when off the gas pedal, this will typically be failing drive shaft u-joints (rear more common than front).

But, if the condition persists at speed, even when not loaded (like coasting at 50mph down a hill) then this is usually related to wheels, tires, or alignment (or a mixture of the 3). Such as damaged wheels (out of round), tires out of round, unbalanced, etc.

 

The O.P. said that he has already replaced the axle u-joints without a change in the behavior.

 

OP should check if his turn stops are in place on both sides (on the knuckles). Even if the u-joints are changed/brand-new the XJ does not do well turning at the full rate. It especially struggles when in 4wd (when load is actually applied to the u-joints).

It goes back to a problem with using a single u-joint on each side of the axle. As a u-joint is deflected it does not make a rotation at a constant rate (unlike a constant velocity (CV) joint). In order to have a constant velocity with u-joints it requires at least 2 u-joints be used any time the rotational force changes direction (like on your drive shaft where constant velocity is a must). But on the front axle there is only one joint - which means the more you deflect your wheel the more that joint's velocity (rotating) is not constant. Meaning, it goes faster for a bit, and then slower for a bit as it makes a rotation. So when making a full deflection turn (like in a parking lot) it can lead to that hopping, jolting feeling that leaves you thinking your u-joints are about to explode. It will be particularly apparent on surfaces where the tires are gripping very well, because they can't scrub/slide/skid on the surface.

 

I could totally see the stops being broken off and allowing the wheel to turn too much.

I've never had any issue with turning the vehicle full right or left myself, but I'm also never going very fast or aggressively when I'm doing it, so I've never pushed the limits.

 

O.P. - Does the knock and vibe at high speed --feel-- the same as the the knock when turning?

 

Completely different.
Im going to check everything everyone mentioned above this weekend.
Thanks everyone for the time you spared to help me out. Much love.

 

Full left would be the right front hub bearing complaining and vice versa for a right turn. But, you mention shaking and knocking at 50 mph which would be a shimmy caused by a loose tie rod. That all said, does the truck drift off to one side or the other at speed causing you to constantly correct? If so, it's definitely tie rod or steering related. If not, then I'm thinking you need to park it and check your hub bearings. The knocking noise it typical of worn sway bar cushions under the frame straps and a loose tie rod shimmy will definitely keep that bar noisy.

 

I would check the LH engine mount, using a mirror, just to be sure...if the rubber is rotted away, the engine can bang around a lot

I would also check the trackbar has no play, this part stops the entire front assembly from moving side-to-side under load.

most older vehicles have more than one thing that is worn, even if preventative maintenance has always been carried out by-the-book

In addition to the other things previous posters advised

 

Just as an anecdote on the tie rod causing shimmy - I had all new steering parts, and I got a vibe right at about 55. The driver's side tie rod was torqued as much as I could get it, but the knuckle must have been wallowed a bit since the stud would spin in the knuckle. Between that and the grooves in the pad sliding surfaces and a sticky caliper, I bit the bullet and replaced the knuckles as part of the brake job.

Note that the tie rod end DID pass the strict MA safety inspection in that state. It just didn't pass my tolerance for vibration and exceeded the acceptable level of "old Jeep clunky-ness" for me.

The stud on the TRE went right into the new knuckle and was solid and no longer spun, so I could torque it to spec. As soon as the TRE was tight in the knuckle the vibe completely disappeared and now my Jeep drives solid and smooth at all highway speeds.

So the lesson is, yes, even the slightest fault in the front end can make a difference.