I have purchased this 88 VL few weeks ago and i am experiencing some problames with the gears(auto trans) especially when i am on freeway the car slightly shakes as it changes from 3rd to 4th gear then it runs fine and the same thing happens during downshift aswell,all other changes occur smoothly.the previos owner adjusted the gear rations 3.9 -> 4.11 could this cause the problame?