Quote:
Originally Posted by allan5oh
I looked up the number and a 10 speed direct has a 14.8:1 first compared to a 14.4:1 first on the 18 speed. Not much difference. The problem is I think doing this is useless because the 18 speed simply drags a lot more than a 10 speed ever would. I would consider a 15 speed deep reduction with a 1:1 final over an 18 speed any day of the week, especially hauling heavy. But they don't exist on truck paper. But speccing new they do.
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How do you figure 18 drags a lot more in direct drive? Which was the point I was making. There is no parasitic loss as the the input and output shafts are essentially linked across and you are using no other gears in direct. It makes no difference if you are using a 10 direct, a 10 OD in 9th, a 13 in 11th, or an 18 in 16th. All are direct 1:1 ratios. The only issue on using a taller ratio with an 18 is that you would have to start out in a lower gear than you would with something like a 3.55. Even then, except in the most extreme cases, you would not have to start out in first unless you were trying to pull the barn down. Can't even recall the last time I used 1st to start out. And I live rural on hilly gravel roads (i.e. extremely muddy when raining) and have no problem at 80K weight. And there are several folks that are having good results with an 18 with something like 2.79 rear ends and are pulling on the heavy side. Then when light, no wind, flat ground, etc... just slide it on up into 17th and cruse along at a lower rpm. Nothing exists that says you even have to use the top hole or even the top two gears, if one runs slower. That is truck driver school stuff and OEM literature.
