Carbonite Cummins was from 2012...
I bet they split the formula into Delvac 50, which is GL-4, and Delvac 75W-90, which is GL-5...
Or I could have forgotten to shake the bottle...
Note that there is a third Delvac transmission fluid, Delvac ATF, which is very similar to Dexron III / Dexron VI...