strange sound from front driver.....

after a few months riding on my 3 in. lift, there this clunking noise coming from the front driver side. it only happens when i reverse out of my dirt driveway. if i hit bumps,cracks whatever no noise. i've check all ball joints (worn out), the only thing i notice is my axle boot leaking. this is driving me nutz

front/rear spacer lift=3in lift
1in front diff drop.

 

I had something very similar, turned out that my inner tie rod end was SHOT

 

do you mean your cv half shaft is leaking....
if so thats a problem