why did they use too make 15 speed trannys then stop what were they made for if the use too makethem

One of the toughest trannys there is, and great for anything you can do with a truck, You just have to shift every gear and do not have any half gears like a 13 or 18.

 

Its basically a 10 speed but with a 3 speed aux section instead of a 2 speed. Its called a 15 but in reality if you started in the lowest gear and progressively hit every gear you'd only use 12 gears. You'd shift through all 5 in deep reduction, flip the blue button to go into low range and shift to 4th in the main box. Then you'd hit 5th, flip the range selector and then shift all 5 in the main box. 3 of the ratios overlap, so they aren't actually useable if you were to shift the way I describe. In most cases I'd just drive it like a 10 unless you needed to start out in a hole or on a steep grade.

 

Yep on pavement it is a 10 speed, unless you are having to start a heavy load on a serious grade. On a typical interstate freight truck, you would not use the deep reduction gears much at all, and even if you do, you don't need to go through all five in it, just shift three change range and go back to the last gear you were in.

 

Why do you think they have quit making them? Fuller has 5 or 6 series of 15 speeds still in production.

Deep reduction is labeled 1-5, direct 1-5 and 6-10. If you do not use D/R you would usually start in 1st or 2nd direct, not 6th.

 

Just don't put it in deep reduction and start out in low range. Pretend the blue button isn't even there. It has an interlock similar to the 13 speed. If deep reduction is selected you will not be able to lift the range selector switch.

 

Low is not actually6th even if you go through all the gears in deep reduction. If you do go through all 5 gears in deep r, you shift from 5 back to 4 in low range. if you just use 3, then you shift back to 2cnd, if that makes sense, it is easier to show someone than it is to tell them. lol
Is yours up against the dash in high gear or normal?