If the 3500 was built as a chassis cab it could have the Aisin 6 speed (as68rc) which uses MOPAR® AS68RC ATF ,,6.8 litres as a service refill or 13 litres for an overhaul. The 68rfe trans uses ATF+4 at 6 litres for a service or 16 litres for an overhaul. ... Login to read more.