So, I guess I could compare a 1500 series truck to my 3500 series truck, they're both used for towing... That's not how it works. For an apples to apples comparison, you'd have to compare 5500 series (or 3500, 2500, whatever) from all three. Not one 5500, one 3500 and one 2500, of course the 5500 is going to perform the best.

I said nothing about transmissions in my post, I was talking about the engines.

As far as aftermarket support for the 6.4, sure there are some making over 700rwhp. So what? I'm not talking about power adders, as there is much more to an engine than that.

Just out of curiosity, what are the years of all your trucks?

Oh you could compare them. I hope your 3500 would win. We are talking fire trucks here. I'm just giving my experence in the multiple fire engines that I have had the privledge of be a part of buying.