I just replaced the bad transmission in my 1990 190E 2.6. The job went very smoothly and was pretty easy. While the new trans shifts and generally performs wonderfully, I have a very, very slight vibration between 40 and 45mph. I paid particular attention to making sure the front and rear driveshaft sections were aligned properly per the markings. Is their a particular orientation for the front flex disk relative to the trasmission and driveshaft? I could find no documentation of such but I am at a loss as to the cause of this vibration. When I say slight, what I mean is nobody but me can detect it. It's there but presents at very low frequency and intensity.

Any tips on where to look next would be a great help.

Thanks,

Sam