any decent gearbox specialists in the north east??

[jim.2007]

just took the 4th lt77 gearbox out of my car as leaking from a seal where the shaft is on the front of the gearbox and also noticed a plastic plug on the top where oil is running out when tilted? does anyone know what this is for, overflow etc? Also does anyone know any extremly good specilaists in the north east who can uprate the box so that i do not have any more problems in the future, taking the company to court who i have been dealing with..any info much appreciated.