Your 1999 jeep wrangler is shaking violently after you hit a pump at around 55-60 miles a hour what is going on?

Answer 1

NOTE: Most shops will tell you all you need is a new steering stabilizer, this does NOT fix the problem, it only covers it up.

You have found a harmonic in the suspension that is common with the type of suspension on Jeep TJs XJs and ZJs. Basically something is worn out in the front suspension or steering In stock from it only requires one part to be worn for this to occur. Luckily almost every part that could wear out and cause this "wobble" is under a hundred bucks. For lifted jeeps WITHOUT a long arm suspension kit this "wobble" becomes more violent and can occur with no parts worn out.

TESTING:

First look under the front of the jeep while someone turns the wheel about 1/2 to 1/4 of a turn in either direction as to shake the jeep. If there are any joints in the steering or track bar (aka pan-hard bar) that show movement the they need to be replaced. Looking at the control arm bushings for any wear in the same way. The final test requires jacking the front wheels off the ground. Try to push and pull the top and bottom of the front tires. If there is any movement it is time for new ball joints. All parts except for the ball joints are cheap/free from parts store/Craigslist. For ball joints go to an alignment shop. They are a huge hassle and require a special tool.

FOR LIFTED JEEPS:

The main cause in lifted jeeps is from the track bar and steering not being parallel. Thus as the suspension cycles the steering has to turn slightly to stay in line with the fixed track bar.(bumpsteer) This accelerates the wear of components and may cause the "wobble" to reoccur frequently even with replaced parts. Shops specializing in Jeep lifts have many solutions including track bar relocation brackets combined with high-steer kits to re-parallel the steering and track bars as well as level them more to stock angles.