I have a 1990 k5 blazer, 4 inch lift, with 33 BFG mud terrain tires. When I am cruising down the road or I accelerate or just tap the brakes it starts to wander the the left and right a little, almost feel like the front is floating around a bit. I have replaced everything from the ball joints all the way up to the steering shaft. I replaced my old steering box with a red head and added a xj steering shaft and it still wanders. I didn't notice any cracks in the frame when I replace the steering box and I also have a Bolt In Steering Box Brace installed. Any ways is there any others place the frame could be cracked at. My next option is to take it in to have it looked. Respectfully

 

Check the sway bar bushings and the leaf spring bushings, especially on the left side. Because of the push-pull steering setup, the sway bar on those acts as a track bar.