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18 spd. question


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There's a nice tractor locally that I'm considering picking up for occasional use. It's an 18 spd. and I'm just wondering if it could be driven as a 10 spd. for the most part just splitting 7th & 8th? Hoping beyerjf or someone who's driven one could give an experienced opinion. We're only pulling 40K lbs.

Thanks in advance -Steve

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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Depending on the final ratio, tire size, engine power band, road conditions, and combined weight......you would probably drive it like a 9 speed unloaded, a 13 speed loaded, and an 18 speed off road.

 

This is based off my having a 13 speed and wanting an 18 speed when off road.

1999 Peterbilt 385 C12 430/1650 13spd

2006 Dodge 3500 DRW 4x4

2010 Hitchhiker Champagne 36 LKRSB

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The 18 also has a lower reverse gear which really helps when you have the tall final gear for running in 16th gear (direct) loaded. Then you have two OD gears for running bobtail at high speeds.

1999 Peterbilt 385 C12 430/1650 13spd

2006 Dodge 3500 DRW 4x4

2010 Hitchhiker Champagne 36 LKRSB

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If it's the same as the ones I drove, it has a "low range" which is really hardly ever used. Like "super-grandma". The ones I drove were somewhat duplicates of the bottom gears on the main, like if you wanted to work it up thru the low range you'd do 1-2-3-4-5 and then go to 4 on the main or 3 depending on rear ratio, etc. Today's engines don't need to have their tail twisted like the old ones to get going.

2000 Volvo 635 A/S, N-14 Cummins
"The Phoenix"
'03 KA 38KSWB

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Yea, learn as a 9. Then follow the graduation steps Cooter has above, then skip the types and mix it up and just give it the gear it wants when it wants it. It'll take many many months to get to that point, and then a few months after that before you measure your fuel economy.

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An 18-speed is a 5-speed transmission (L-1-2-3-4) with a two-speed range shift (low range, high range) and a two-speed splitter (sometimes direct, overdrive, other times direct, underdrive). In high range, L gear is a no-go, so essentially it becomes L-1-2-3-4-5-6-7-8. In those nine gears, you can split every one if you want, making it 18-speed.

 

Honestly a 13-speed is exactly what you see above, but with the splitter disabled in low range. A 9-speed is often exactly what you see above, with the splitter disabled completely.

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18 spds are "standard equipment" in our land... like Scrap says just mix and match whatever works... the splits are nice for cruising through towns, back roads etc.

 

The splits are needed hauling 140,000lbs on gravel roads...

"Are we there yet?" asked no motorcycle rider, ever. 

 

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3.55 ratio, 40" (22.5) rubber. Looking at a Roadranger chart, same as a 13spd skipping 2, 4, 6, 8, 10. It'll definitely take some getting used to!

What engine? 3.55's aren't horrible, but 3.21's would probably suit better. Mine had 3.90's and it was on the low geared side so I swapped to 3.36's, but would have gone 3.21's if I lived where the towing speed limit was higher.

1999 Peterbilt 385 C12 430/1650 13spd

2006 Dodge 3500 DRW 4x4

2010 Hitchhiker Champagne 36 LKRSB

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Like has been mentioned above, you are just not going to need to split the gears in low range. An 18 speed is needed for very heavy loads in either hilly or off road circumstances. You will like the "13 speed" splits in the high range. The differential ratio, 3:55 makes sense with the 18 speed, the whole spec is to be able to get some monster load rolling in trying conditions. Engine and cruise speeds are totally secondary. If you can live with those limitations get it. If you can't, look at another truck. I wouldn't even attempt to start changing rears and transmission ratios, not cost effective.

Jeff Beyer temporarily retired from Trailer Transit
2000 Freightliner Argosy Cabover
2008 Work and Play 34FK
Homebase NW Indiana, no longer full time

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I wouldn't even attempt to start changing rears and transmission ratios, not cost effective.

Totally agree! I drove it yesterday... KW, interior was nice but just the engine noise from the short gearing was enough to give you a headache in an hour. Also too many cracks in the bodywork for a 2014. As you surmised about the loads, they haul bricks!

"There are No Experts, Do the Math!"

2014 Freightliner Cascadia DD16 600hp  1850ft-lb  18spd  3.31  260"wb
SpaceCraft S-470
SKP #131740

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