I started this thread a few years ago since my 6spd tranny SUCKS and I was looking to improve the low speed towing - mainly to be able to hold 2nd easier up winding hills while towing my 11K 5th wheel. To date I haven't done the swap just since I don't get out towing that much and am just to busy/lazy to be without my truck for a few days. Also, as the years tick by it seems throwing 2K into my truck for an optional upgrade isn't the smartest financial decision. I'm 6 years in and almost to 100K.
Anyway, I'm intrigued with all the discussion about RPMs in 4th/5th/6th gear while towing. Honestly, that never even entered my mind. RPMs while flying down the freeway at 80 (without a trailer) is a factor but I guess I don't think that I'd know (or care) about the difference if I were rolling along at 65 in 6th with 5.13 gears or 5th with 4.56 gears. If the RPMs are the same isn't the power the same? It seems each ratio might have its own "sweet spot" but the upper gears seem to be pretty close together so a different ratio could just be compensated for with a different gear. (which is basically my complaint with this tranny.... large gap at 1-2, tight spacing at 3-6)
I'm not a MPG micromanager at all.... especially these days with gas prices. Is this a MPG thing? Or, is there some other reason it matters what gear you're in while towing at a common speed like 65MPH?