vibe

'01 F-250 SD XLT 7.3ℓ 4x4 While in 2WD and slow speeds, Drive over a bump and a vibe starts coming from the front end. The ways I have found to stop the vibe is to: Engage 4HI, stop, or hitting another bump works sometimes. This does not happen while in 4HI. Could this be the 4WD driveshaft...