Vibration in overdrive
I have a 1989 Chevy Celebrity Wagon that has 105,000 miles. I Had all the vacuum lines under the hood replaced because of a slight rough idle. Some things were rerouted and I wanted it all original. I drove about 125 miles parked and two days later when I got on the highway it would vibrate the car in overdrive. If I put it in third or kicked in to passing gear it would stop. I replaced the map sensor and transmission modulator but it is still doing the same thing. Any suggestions? it may be two separate issues but they happened so close together I am confused.