when and only when i hit 70 does the front end shake when i apply the brakes.I had done alot of work to the front end and both sides shake. the tires are 265 65 r16 and one on back left is 235-65-r16 (having it changed to match tonight). the front drive shaft is out im putting it back in aslo tonight. What else could cause this.

I would check for warped rotors.

That's a pretty classic symptom of warped brake rotors, but also make sure the wheel lug nuts are properly torqued.

After having the rotors machined or replaced, be sure the properly torque the lug nuts in the proper star pattern to reduce the chances of the rotors warping due to lug nut tightening.

-Rod