Jack it up, remove the tires and reinstall a couple of lug nuts to hold the brake rotor tight. Put it in drive and watch the axles and see if one is bent.
I replaced a bent drivers side axle last year on a members car that made the EXACT clunk clunk sound. It was the axle pushing on the brake caliper every revolution but you would only hear it at slow speeds.
only sound on D, In 1 or 2 selected no sound....
He let it get so bad that the pads wore away all the metal for the brake pad slides and I had to replace the caliper bracket..
Just watch it rotate with out tires and make sure it turns true and isn't bumping into the brake caliper every rotation. I did that one day....no sound
My bet is on the axle being bent at the outer end.