I'm experiencing a 25-50mph driveline vibration, worst at 35mph. It happened over a 7 hour round-trip, I didn't notice anything until we were off the highway. It hasn't gotten any worse since then.
I can feel a vibration through the gas pedal, and can hear it faintly. It's a pulsating vibration, and doesn't seem to correspond to acceleration/deceleration, turning, etc. The pulsation does speed up with vehicle speed.
I've been assuming for now that it's a driveline vibration. I checked the angle gear for oil and it's full. Turning does not make it better/worse, so I doubt it is angle gear or wheel bearings. I'm thinking either a front axle bearing or the drive shaft.

The driver's side axle has quite a lot of lateral play where it comes out of the transmission, is this normal? I would say around half an inch.
The passenger side axle felt fine to me, no play.
The driveshaft doesn't seem to have play either. Could I simply unbolt the driveshaft at the transmission and diff without removing it to test it, or would it clunk around?

Thanks for any help.