i have 05 with the allison 5 speed.i was going to do a fluid change on it my self. how much fluid does it take and what fluid do you guys think is best

Pan drain only 7.5 qts, add 2.5 qts for deep pan

Full flush 12.5 qts, add 2.5 qts for deep pan

These are estimates that I have I accumulated through various threads, but seem to be the norm. I just did a deep pan drain and flush and used 4 gallons.

the truck has 55000 miles on it and the fluids been changed once.should i drain it are flush it