Still need help with vibration noise

I am still trying to find this vibration noise on my car and i cann't figure it out. It only makes this noise in every gear and at 2400 rpm. No where else will it do this not even reving the motor standing still. So far i have changed the following: Bad rear shocks, Crossmember bushings, motor mounts, and check everything by tapping on things with a hammer (which nothing stuck out like it was the problem). I am coming to a dead end at what to look for next. I am starting to think that maybe the drive shaft or mufflers going bad, but then i would think that it would make this noise elsewhere not just one spot in the rpms. A friend rode with me and thought it was coming from the rear but i think it sounds more like the middle to the front of the car.

Just looking for some more help on what i could look at. Got do be something in the driveline i guess.

i have check the cross member and the exhaust. both are fine. unless my mac mufflers are rusting out from the inside. i tried one time to jack it up but it would not make the noise when i did. don't understand why. i will try that again though to see. thanks guys

i can feel the drivetrain vibrate around there but i hear a noise. i took it for a ride just now and it stopped doing it after i drove it for a bit. stop then left again and it was making noise then stopped. now it is not doing it all the time. i am really lost now.