2004 Chevrolet T7500 Engine: 7.8L L6 DIESEL; Position: Fan, Alternator and Air Conditioning;. 2005 Chevrolet T7500 Engine: 7.8L L6 DIESEL; Position: Fan, Alternator and Air Conditioning;. 2006 Chevrolet T7500 Engine: 7.8L L6 DIESEL; Position: Fan, Alternator and Air Conditioning;.