Question: what is the difference between a grand national and gnx?
Answer: There already is an engine oil cooler in the Grand Nationals, and the GNX adds a cooler for transmission fluid, though that's the only change to the Turbo Hydramatic 200 4R. ... Buick had already reached the limits of the Regal's suspension with the Grand National, so the GNX is beefed up still more.