best rear end 240sx 95

[gismonismo]

hey guys.my build up its almost done 700+hp RB25det S-14 sow far its all been fun and the car its boosting att 21psi for the streetbut my rear end aint helping me out,when I hit high rev the dif makes a sound,its in the 800 to 900 rpm range when the sound kicks in.I know theres no one making good horse power on this engine(above 600hp range)so hope some of you have a Idea for a good dif?Anyone knows the tec blah of the Q45 and the 4.11 300Z is?please explain why and witch one is best for my new proyect Thanks