How bad is using low gear in high range in an 18spd fuller? (Driving it like a 20spd)

Posted by Far_Somewhere_8425@reddit | Truckers | View on Reddit | 21 comments

How bad is using low gear in high range on an 18spd fuller? (Driving it as a 20spd)

Hey, I'm an owner operator and I've got an 18spd in my truck. I work for my dad's business and he taught me to use low gear in high range, which a lot of people call the ghost gear I believe.

4th high split in low is 2.73 ratio, 1st high split in high (aka 5th high split) is 1.95 ratio, the ghost gear low with high split in high is 3.29. Physically these 18spds are 20spds but they say using low gear in high range is damaging. I get why, the torque multiplication is dangerous to the range box.

But my dad has been driving this way for decades, and never had a trans issue, and I've been driving using the 18spd as a 20spd for 8 years since I started, and never had any issues.

How bad is it really to use these gears? I find it convenient to not have to switch the range box, even though it's a lot harder to rev match and float low, gotten used to it though.

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Then-Bet8731@reddit

I do it occasionally in my 13, when I need a few more rpms, but don’t want to shift to the low range. Going around faster corners is where I mostly use it.

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Ozdriver@reddit

I don’t see why you’d bother. I’ve got an 18 in my truck and trailers and it’s usually at 79 tonnes / 174,000 lbs and it’s perfectly adequate using the 18 as Fuller intended. I remember a transmission specialist saying there was a reason not to use that “funny” gear but I’ve forgotten what it was haha.

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Chiknlitesnchrome@reddit

The reason is that your gear is only partially meshed with two different gears on the trans, and isn’t in full contact, so a lot more strain, on it, and if it chews through it while using that ghost gear, well guess what you now lose that hole, meaning you have no low, low, or low hi, and you have metal in your trans now

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anxious_polarbear@reddit

Isn't lo gear in high range the same ratio as 4th in low range? Helpful in a 13 because you can split it, but pointless in an 18 because you can already split 4th.

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Far_Somewhere_8425@reddit (OP)

No it's not, low in high is a higher ratio. It's a different ratio to all other gears.

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anxious_polarbear@reddit

Well it's close enough that I can't tell the difference.

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acs0311@reddit

Occasionally I’ll use the “ghost gear” while downshifting while rolling down a steep exit ramp or into town. Did it yesterday in TN taking 243,000 lbs down a 7% grade ramp to a stop sign. Otherwise I don’t use it. If it’s there use it.

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Far_Somewhere_8425@reddit (OP)

Thanks, I only use it when downshifting as well

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fightfire28@reddit

It’s called the cheater gear by old timers, there are situations where it is helpful and there are no issues with using it.

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Far_Somewhere_8425@reddit (OP)

Awesome

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pervyjeffo@reddit

Perhaps I don't understand the circumstances in which you use it. Do you mean you go from 4 over, to Low over, to 5 direct? Or do you ride in Low over before you go into first?

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Far_Somewhere_8425@reddit (OP)

It'll drop down into it when I need it, I don't use it when accelerating because low high high range is a higher ratio than 4 high low range. So that would be a downshift.

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Supertrucker82@reddit

I don't think its bad at all. I also don't think its really necessary. You got plenty of gears already. The only time I have ever used low low gear is from a dead stop on a super steep hill fully loaded. Once your rolling and went through the whole low side of the Trans grabbing that ghost gear is pretty pointless.

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Far_Somewhere_8425@reddit (OP)

I find it more convenient than swapping range

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sk8zero0619@reddit

The problem is floating it into ghost gear in high rpm. I always clutched it

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Vast-Yak-8713@reddit

It’s fine it’ll be ok

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JOliverScott@reddit

I think it's mostly just about powertrain protection so that a novice driver doesn't strip gears or blow out a gearbox. Megas had problems with drivers wrenching u-joints on driveshafts because they didn't learn how to properly drive with a clutch so instead of teaching them fleets just switched to automatics.

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ursisterstoy@reddit

It’s not a big deal as long as you don’t try to go from 4 high to low low in high range. Low in an 18 speed is a slightly bigger jump than between every other gear and 4 high into 5 low is about the same amount of jump as between all the other gears. If you went from 4th gear to low in high range you’d be downshifting but you can skip 4th and go to high range after 3rd and it would not matter as much because you’d still be going pretty slow and you can shift to 5th from there and keep going.

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