in the past two months i have replaced almost all tie rods, track bar, shocks steering stabilizer, rotors and break pads, and got all 4 tires balanced. everything is still tight and functional tires balanced today and rotors and pads replaced yesterday. yet i still have a shim when i am driving on the highway. please help

 

Sounds like a U-Joint to me,.

 

which one would it be and how many are there (not inside the axle)?

 

I had one in my 96 replaced everything in the steering, wheels, tires,ujoints, drive shafts, everything I could think of it was still there 240,000 miles later I guess it is just a jeep thing.