Mercedes Sprinter 2007 Automatic XLWB High Revs?

[TTinkle]

Hi. I have recently purchased a Mercedes Sprinter 2007 Automatic XLWB minibus with Tacho & double rear wheel, plated at 5 ton. At 60 mph its revving at around 3K! I have asked around and it seems it may have a low speed/ high rev ratio diff fitted as it was a city mini bus? Can anyone throw any light on this please, either information on the diff or preferably any advice on how to change this to a standard sprinter ratio if possible? If anyone knows how to remove the tacho that would be good too! Cheers TT