Ok I just got home but barely in my 2001 forester s with 184k miles on it. The previous owner definitely neglected this car. I replaced the engine a month ago and have put 3500 miles on it especially from this trip from El Paso, Texas to Leavenworth, Kansas. I have this vibration/hesitation feeling/clicking/popping sound coming from the front end. Over my 500 mile drive back, it got worse. How to tell the difference from a center diff issue and a driver front axle issue? Both look in good condition and not torn or leaking. It now makes this noise when I turn backing up in any direction, accelerating forward, and its worse going up hill and turning. It feels like it hesitates but the RPM's don't change. Its definitely a drivetrain not engine issue and it does it all the time now, cold or hot, fast or slow. It gets better when there is no load on the drivetrain and when the clutch is pressed in and turning then it doesn't pop. Any help where to start or advice from experience is much appreciated. If you would like a video I can make one later today. Thanks.