I have a Ford F-350 2002 Diesel Crew Cab Long Box 4wd dually with the ZF 6 speed manual trans. Mine has the oil cooler and pump. Would I be better off using a manual transmission fluid or Mobil 5-30 HM than ATF. It lives on our 4 horse goose neck. It only has 129,000 miles on it but it has never been changed yet. The truck is bone stock but I have plans to bump it up a little.