Last month or so some times when I go to do a pull and change from first to seccond it clunks in the rear end and flickers the traction light on and of a couple times and has 0 power when I hit seccond bogs out I come of the gass shift down then back to seccond and goes fine again? Doesn't happen much just occasionally just curious if this is diff or gear box ? 

This is a few months since but not sure if you still have this problem. 
 

I get a clunk in the rear on my FG XR6 Turbo and when I jacked the car up soon after buying I noticed my nolathane bushes were split in the cradle (not a big split and its still all together). It will clunk at low speeds if you accelerate hard and take your foot off the gas. If I hit a bump really hard, my traction control light will come on. I then have to turn it off and then turn it back on and drive for a little while and it is back to normal again. 

I'd say it could be your diff bushes. Check them first, then the diff possibly itself. Don't know why you get zero power unless the ECU is putting you in a limp mode of some sorts. I'm still new to FG falcons (not new to cars) so not sure if they do this. 

Cheers bud I too have nolothane bushes so will check there about 25xxxkms old so could well be but now I just do pulls with out traction control on and have no issues atall , but I think a axel may be on its way out when I go to turn I hear like thuds not all the time but when I pull out slow or something never does it at speed , and I'm too cheap to take it to a shop to diagnose 🤣