Cast Iron Cases

• The GM transfer case can be identified by its cast iron casing in GM Blazers and K series trucks made before 1984.
  
  

Aluminum Cases

• In GM Jimmy, S10, Suburban, Tahoe and Astrovan models made between 1988 and the present, transfer cases are made from aluminum. The ones in the Jimmy and S10 models are light-duty cases; the rest are medium-duty cases.
  
  

Magnesium Cases

• GM's line of K3500 trucks, as well as its Safari, Bravado, Typhoon and Cyclone models from 1987 to the present sport magnesium cases. The K3500 cases feature oil pump spacer plates.