so under shifting the manual transmission or suddenly acceleration it does hard shocks to the differential
i put the transmission in N and put the handbrake on and got play between the ring and pinion gear (here a video http://sendvid.com/5ldtixzn )can i readjust the ring gear ?
how much play should be there ?

 

Can't really"adjust" anything.

It probably needs pinion and carrier bearings.

 

rear end looks like has little extra play really needs torn down to inspect parts and bearings

 

I think if it were the pinion bearing the U joint flange would wobble around concentrically. It's nearly unrealistic to have significant play between the ring and pinion gears and not have a rear end that whines incredibly or can still turn. My bet is that your carrier needs rebuilt.

 

Thank you so you mean not the pinion maybe the diff itself ? The car doe have 121000 miles on it

 

Yeah, at 120K miles I'd say the carrier needs rebuilt. Might as well do bearings while you're in there.