wmoses wrote:I wouldn't get too hung up on fuel economy differences between these two rear ends. Really, I wouldn't. The change is very minor (11%). All it means is with one you'll be spinning 11% less RPMs. That does not equate to 11% better fuel economy. In fact, it may equate to worse fuel economy, depending on the type of driving you do. If you do a lot of stopping and starting, as I do, a lower (numerically higher) gear is more advantageous to fuel economy. If you drive all freeway, the opposite is true. That said, I'd be very surprised if either of those two rear ends produced any measureable difference in fuel economy.Even if the rating were linear, it would mean that 7000# becomes 7700# which is greater than the GVWR of the RV I am contemplating, while at the same time not impacting my fuel economy as much as a lower gearing would. Since this truck is my daily driver that is very important.
wmoses wrote:I don't think the relationship of "tow rating" is linear with respect to anything since it doesn't make a lot of sense to begin with. There's no magic going on here. The laws of physics say you'll get 11% more torque, the "tow rating" number says you can tow 37% more weight. Which do you believe?The reality is, if GM can rate their 3.42 geared truck with my configuration at 9600# (+37%) then the relationship is not linear with respect to rating.
wmoses wrote:Try dropping a gear while towing. Like I said, it'll give you a lot more torque, and it's free.At the end of the day, I would be going for more than the RV GVWR that the new ratio can give - whatever that margin is - and I still hope to get close to the usual non-towing 17 mpg average I get now.
