18 speed

Even grossing 120-130k I rarely split the bottom unless I'm off Road.

 

You'll only ever need those low-end halves if you are grossing over 100,000lbs and starting from a dead stop on a hill.

Unless you've got 2.90 rear ends, you'll probably never use them. I drove a 3.70/550 CAT/18-speed combo with 137,500 lbs gross on B-trains and started in 1, shifted 2-3-4-5/O-6/O-7/O-8/O most of the time.

 

Owner-operator spec trucks generally are spec'd for variety. The ability to take any load anywhere in the country. Company trucks (9 or 10 speeds) are spec'd for the regions that company operates in, so if they don't do a lot of hills (and even if they do, those transmissions are cheaper) they don't need a lot of power or lots of gears.

They are spec'd for fuel efficiency first and foremost, and the pencil pushers in the office ordering the trucks don't understand what it takes to pull 80,000 lbs up a 10 mile-long 8% grade, so they get the 400 hp 12-litre with the 9-speed and 3.25 rear end governed at 58 mph and wonder why all the drivers are complaining.

 

I gross 140,000 quit a bit. I usually only split 6th, 7th, and 8th.

 

i drive an 18 speed milk truck, i rarely split the bottom gears, one exception being a steep hill i climb to one of the farms. on completely flat ground i would only maybe split 7th and 8th. everything around here is hills though and the truck is usually around 90-100K gross. splitting really isnt necessary too much on flats especially at only 80K

 

If it feels like it is lugging then split them. If not, no need to split, you are just adding more wear and tear on the tranny. On an flat, loaded 80k, I typically take off in 1st and don't split until I hit the high range.

 

Well how about this truck I'm thinking of buying. 2001 Western Star. Pre emissions of course. How to frame rebuild Detroit with new 18 speed. I have not seen the chart yet but he saying 610 horsepower.

 

(Necro alert!)
This thread is very helpful, thanks guys.

I just started hauling sawmill chips, after driving automated 12 speed for 8 months. I had the same questions as OP, and I'm glad I searched before starting a new thread.

Well haul pretty heavy, with possum belly triple axle trailers. This is in NW Montana and southern BC.

I was intimidated by the 18 speed at first, but my trainers have been very helpful and patient, and my shifting is coming along nicely, although I have a long way to go.

My biggest problem right now is getting back into 2 and especially back into 1 rolling at stops, but I'm gaining ground slowly.