I reckon its the crown n pinion wheel... they're probably just scuffed... cuz maybe at one stage there wasnt enough oil in there...
Does the noise come on when ur on partial or no throttle...but if u floor it... the noise goes away...? If thats ur problem... its nothin major... and should still last for a while... Just make sure theres diff oil in there...
I personally wouldnt bother fixing it... just get the money together and go for a T series...
