Hey 4.3,
That's not always true...you can find 2-speed rears that have better high gear ratios and give about the same ratio in low as the original single speed rear. I did this on my fire truck. It has an Eaton rear and I just replaced the center pumpkin. I went from a 7.17 single to a 6.14/8.36 2-speed which gave me a lower low and a higher high. I gained 10 mph and now run in the low 60's all day long. Total cost fot this was under $400 ($250 for the rear and $100 for a drive shaft and about $50 misc).
I think this is the cheapest way to gain speed while keeping the pulling power to haul a load.
Mike B
