If you put one 2 speed differential in the front and one 2 speed differential in the rear, wouldn't they cancel each other out.
:confused3:
thats exactly what he was saying
Using a 2 speed rear end in the back only, means that the front axle only makes the same speed as the rear end in either hi or low, if you shift the rear end whilst in 4wd it will eat tires like mad.
In Europe most trucks under 12 ton use a six speed, 12 ton with trailer has an 8 or 9 speed. The Volvo F89 of the 1970's had a 16 speed, but modern I-shift is only a 12 speed, because of the increase in horsepower per tonne ratio, as well as the much flatter torque curve of the last 15 years.
With a high power to weight ratio the acceleration is so fast that it takes more time to change gears than to actually accelerate to the next shift point: its just not efficient.
Only with a dual clutch design like VW is using, or Deere in tractors (Direct Drive) its useful to have more gears, because shifting occurs in milliseconds. With conventional automatic transmissions its no use either, because it has a torque converter to overcome gear differences, and using more clutch packs means more drag losses. The beauty of a dual clutch gearbox is that as the name says, it has only two clutch packs creating drag losses, and the speed difference between the two is never more than the ratio difference between one gear and the next, while auto transmissions make the 1st gear clutch slip as fast as the 6th will spin it.