Either someone popped 2500 badges on or worse (and most likely), someone stole the 3/4 ton axles (better ratios and bigger brakes) and swapped in 1/2 tons. They are a direct bolt in swap between 1/2 and 3/4 tons.
How is it worse? It really isn't any different. They are the same axles that would have been under it if had been a 3/4 ton. A 10 bolt front and a 14bsf rear.
Martin
