First i will give the history on this 98 blazer 4wd 245,000 miles . I just bought this truck a week ago knowing it needed front end work and tires so here is a list of what i replaced.

Both front Axles new ones advance auto
all 4 ball joints
inner outer tie rods
both front wheel bearings
front end alignment
4 new general grabber tires
new brakes all the way around.
new shocks all the way around

Now here is the problem truck drives straight as an arrow , brakes are perfect no pulsing no steering wheel shakes. drives pretty smooth up to about 50mph then i start to get a vibration in the front and it continues to worsten at 75mph the truck is shaking pretty hard .

what should i be looking at next i was thinking a seized u joint any other suggestions.

 

i would try the u joints...but i would also look at the steering stabilzer not sure if you changed that...