How many quarts of transmission fluid is needed for the Dually Model? on 2002 Chevrolet Silverado 3500

I need to know how many quarts of transmission fluid is needed on my 2002 Chevrolet Silverado 3500 Diesel Duramax 6.6L V8 Diesel Turbo Dually?

DO YOU HAVE AN ALLISON OR 4L60E OR 4L80E TRANS
Allison
are you just doing a service or is completely empty?