what on earth shall i do with this pinion yoke?????

. you said that you checked the pinion angle, both ends of the drive shaft need to be at the same angle, when you put in the springs ,you raised the back of the car ,thus raising the angle of the tranny . if every thing else fails to fix the problem I would look into the drive shaft angles.. they must be equal, other wise one u -joint will over speed the other one ,this can cause a hi pitched vibration. also make sure the car is sitting on its wheels when you check the angles, I have had to shim a tranny or the cross member to correct a problem like this before. this one is a long shot, but when all else fails, we need to check everything.... good luck