I'd assume R134a since R-12 was banned in 1994.
R-134a
How many onces for 134A refrigerant does GMC Sierra use?
134A
NO.. They are a different type.
The refrigerant capacity of the 2002 GMC Yukon depends on the type of air conditioning system the vehicle has. Front only AC has a capacity of 28 ounces. Front and rear AC has a capacity of 42 ounces.
The 2012 GMC Sierra-2500HD has overhead valves (OHV).
The 2008 GMC Sierra-3500HD has overhead valves (OHV).
The 2014 GMC Sierra-3500HD has overhead valves (OHV).
The 2007 GMC Sierra-3500HD has overhead valves (OHV).
The 2008 GMC Sierra-2500HD has overhead valves (OHV).
The 2010 GMC Sierra-1500 has overhead valves (OHV).
The 2011 GMC Sierra-3500HD has overhead valves (OHV).