Hi I have a 2002 ford ranger xlt automatic with the 4.0 engine, it's transmission shifts ok when in drive but when going from reverse to drive CACHUNK goes the trans and the car shifts. What's wrong? Do I need a new transmission? Or can this be fixed

 

It's probably not the transmission.
A few other things to check first.
Transmission mount, U-Joints, Slip yoke on drive line, Pinion bearing in the rear diff.