Jaybird1980
Grandmaster
Ujoints is where I would startIt definitely does not vibrate like that under 75. It's all drive train, for sure. I feel it in the shifter, not in the wheel or pedals.
I want to say 5th @ 75 is about 2800rpm and I know that rpm doesn't vibrate like that in the other gears.
I haven't taken the driveshaft out and inspected ujoints yet.