Vibrating steering wheel

:banghead: We just bought a new 2006 Ford Escape in June. It has a V6 and all-wheel drive.
You can feel a shallow, subtle but very rapid vibration in the steering wheel and floorboard. It starts around 45 mph. In July the dealer said it is normal for a Ford Escape to do this. It is part of the all-wheel drive system.
It just doesn't feel right. For the first 300 miles of driving this condition didn't noticeably exist. It just seemed to start between 300 and 400 miles of driving.
A squeak developed also around this time. The dealer said we had a bent axel, and they replaced it. The squeak went away but the vibration did not.
Does anyone have any thoughts?

You say the vibration starts at 45 mph but do not say if if goes away.
Usually a vibration from tire balance starts around 50-55 and goes away at 65.
Check the tire pressure first, a lot of dealers ship vehicle with too much air in them. Should be 29 all the way around (V6-auto-awd...but I put 30 psi in).
If tires are at 30 then add some and try it.

If it is not the tires, then I would look at the engine and trans mounts. Then at the steering column. Make sure no engine hoses are touching the steering or the body.