18 gears. WTF Chuck?

I was told less moving parts, less things to break. 10 spd last longer & cost less ro rebuild.so I am told. I started out in a super 10. still driving it. 1.2 mil before I had original clutch replaced. still going with out any problems, never rebuilt at over 1.3 mil now. I usually gross 75,000 lbs. I really cannot make a comment witch is better or witch I like better, having driven only one type trans.

 

you go thru every single gear. do you use the clutch between shifts?

 

I don't know why he would think that going through every gear is gonna make the clutch last longer...My last clutch was replaced at 900,000 miles, Not because it was worn out but because I replaced the tranny and I always replace a clutch when I replace a tranny.


It would have easily gone another 100,000 miles had I not needed a new trans.

 

Sounds like a lot of extra work and wear and tear on the trans. for no reason to me.

I'm doing this in order to get 1 milion miles out of the clutch. It might be surprising to some, but that is exactly purpose behind 18 speed transmission.[/QUOTE]

Funny....I always thought that the reason for being able to split the lower side of the box on an 18 was so you could get a VERY HEAVY load moving with less strain on the surrounding components...I hardly think that they sat down and said "We need to design a transmission with more gears so that guys don't wear clutches out so often".

If you are easy on a clutch they will last a million miles and if you are not...You'll be replacing the clutch well before that, But it won't be a big deal to replace the clutch because you'll already have the trans. out anyway because if you're that hard on a clutch, You're hard on a trans. too!

Don't try it driving local, people would shot you down [/QUOTE]

 

For a 80k rig, the advantage is in the top end of the transmission, when you're climbing hills.

For heavy haulers, the advantage is clearly the 18 speed, where you can split the low end of the tranny for easier starts.

But, for pure fuel economy, (especially 80k rigs running mostly flat ground) the best choice is a direct drive 10 speed (not an overdriven 10 speed). Why? you ask........ because, in the case of the 13, 18, and 10 speed overdrive trannys, they all use an extra set of auxiliary gears to achieve the overdriven ratio. Extra sets of gears and shafts = more mass and friction to be overcome by the motor, hence the use of a little more fuel. You'll see about a 1 to 3 percent advantage in fuel economy, by using a direct drive 10 speed rather than ANY overdriven transmission. BUT, with that same 80k rig, if you're driving primarily in hills and mountains, then I believe the advantage goes to the 13 or 18 speed, where you have the ability to split the gears on the top end and stay in a more desirable rpm range.

In my opinion, the 10 speed overdrive transmission, is an odd transmission, and I don't see the advantage of having one. You can't split the top end, plus you have the disadvantage of using auxiliary gears. Maybe someone can shed some light on this type of transmission, as to why they're even used.

 

That has been debunked. In theory it gives you about half a percent better economy not having the extra mesh. In reality it gives you nothing, and on top of it it wears out the rear axles far faster due to the extremely tall rear end ratios.

Nobody recommends spec'ing a truck with a direct drive 10 speeds anymore as all you get for it is shredded pinion gears.

 

Maybe...But I doubt it.

The amount of fuel you'll save based on that criteria alone will be so nominal as to not be noticeable.
If you drive the truck correctly the transmission is going to have little if anything to do with your fuel mileage.
You can straight shift a thirteen or eighteen speed when you are light or empty...But you can't split a ten speed ever so when you want to keep the motor in the most efficient operating range on a grade, You can't! The extra fuel you'll consume by having to deal with the wider ratio splits in a ten speed will more than make up for whatever fuel I'll use with the "extra gears and shafts" as you say in a thirteen or eighteen!

By the way...You do know that the front half of the trans. is essentially the same in a ten speed and exactly the same in a nine speed as in a thirteen and an eighteen speed trans. and that the difference is in the back of the trans. and doesn't really add that much drag over the nine and ten speed versions don't you?

I've had these gearboxes apart myself and there is just not that much additional drag created by the additional gears

Again...This comes down to knowing how to operate the equipment!
In many situations I find that being in overdrive helps my fuel mileage and there are many situations where being in direct is better, The trick is to know when you need to be in what range.

There you go...I would extend that to say that there is never an advantage to a ten or nine speed transmission if you know how to operate the equipment efficiently!

That is why fleets buy ten speeds and nine speeds...Because the vast majority of fleet drivers these days are little more than seat warming steeringwheel holders and have no knowledge or interest in knowing how to properly operate the equipment.

We are in complete agreement here...
I bought a truck with one in it about twenty years ago...I ran a few trips with it and came to the conclusion that it wasn't a very good set up.

I removed it and had a thirteen speed box installed.

 

I stand corrected.

your comments are a good example of "real world experience" vs "book learned experience" (mine).

Thanks much for the info.

 

Sometimes it looks good on paper but just doesn't hold up in daily use.

 

I wasnt going to enter this arguement, but as long as it has been brought up.....
I agree, i always start in low, even empty. But explain to me how using every gear after that is going to make a million mile clutch? The only clutch wear should be in the starting gear? I look forward to learning more, right here...