I own an 88 300 SEL with 164,000 mi. I have noticed a vibration between second and third under moderate to hard accel. Both flex discs have been replaced as well as the center support bearing and rubber support. I change the trans oil every 30,000mi and the oil is clear red with no particulate matter in pan. I have owned this car since 98 and am very familier with it's "personnality. Could the problem be the U joint?