I install in a ib5 gearbox with rear starter mount a quaife differential with new bearings and ford racing puma internals , the problem is in the diff, when I close the gearbox it's blocked!!! no running free!! I don´t know whats happening

 

Did u get the diff shimmed correctly?

 

the diff crown wheels are different thickness on the ib5

 

Try and mark the edge of the crownwheel with a marking dye, engineers blue or similar, make sure inside of gearbox casing is clean, and bolt it together quick, it should leave blue dye anywhere it touches the case, then you can file/machine/grind it back to fit?

 

the problem was with 4th gear main shaft . I will put a photo