Kind of Off Topic

I hope I can plumb the collective experience and knowledge on this site. My 77 Cordoba has a high frequency vibration shortly after starting up from a stop, starts to kick in at about 20 mph, continues from there and on. Here is what we have done so far:

1. Total front suspension rebuild, idler arm, bushings, tie rod ends, ball joints, steering box.
2. New ESPO rear springs (second new set, trying to solve by correcting pinion angle)
3. new u-joints
4. new tires/balance

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Kind of Off Topic