BNR34 new gearbox rebuild still making noise is it oil or bad build

[Htowngodzilla]

BNR34 new gearbox rebuild still making noise is it oil or bad build

Hi guys 

so I when I was building my car thought I go ahead and change bad syncros and the mechanic said I also needed few gears as well.  It's been I year and  1/2 I just never used the car cuz been under restoration and engine build. So I can't go back for Warrenty,  the mechanic rebuild Supra gearbox all day so he suggested to use the Supra gearbox oil from toyota. And  at first driven the car no problem like new.  Then did engine upgrade did dyno but now I come to drive the car I can say been 100 miles on this box and now I hear shine noise when I let go the gas at low speed and plus start grind for some gears. Wtf.  

I even use OS GIKEN thriple plate clutch beside the Clutch noise at  idle. I was told that normal. So I'm ok with that.

but I been reading you guys use different oil on forms. Is my problem oil. Or bad build

thanks

[Chris-06R]

Assuming your mechanic used something like Castrol Transmax Z which is commonly used for Getrag gearboxes in both Supras and 34 GTRs that should be fine.  So it might be something else...  Take it back to the builder and get their opinion.