Gear cog size

Hi, while I'm still trying to get to the bottom of my noisy gearbox episode , I got to thinking are indian gear boxes machined slightly larger regarding tolerances than the Italian ones ? in respect to the teeth & the internal diameter where cogs run on the lay shaft & where the sliding dog catches the cogs ? the reason for the question is could this be reason for the noise as they are a slightly looser fit from new ? I've not got an Italian box to compare to my indian one so can't confirm this . thanks for any info . cheers 
