Hi All,
The car is 1993 W201 190E 2.3 with 256 miles.

I just noticed a vibration above 60 mph ONLY when I am going up hill and trying to keep my speed within the flow.
There is no vibration in level roads at any speeds.

Alignment and balance is ok and was just done recently.
Both Flex disc look fine with no cracks or damage at all.
The vibration is gone if I let off the gas pedal or accelerate gently.

could this be a bad transmission?

Thanks for your replay.

Also check the center support bearing on the driveshaft. When these wear they can let the driveshaft go out of alignment under torque.

I already checked the center support bearing whan i crawled under the car and it looked fine when I tried to laterly move the drive shaft.