Pre EGR overrated ?

I'll have to get back with you on the rpm's at 80. Will check sunday eve when I head out. I know, that in 16th at 1600 rpm I am at 70, and dropping into 17th there I am around 1350 ballpark. Best guess at this point, at 80 in 17th I would be at around 1550 and 18th around 1300. If the road speed calculation chart I used to look at road speeds in various gears when I ordered this is right, then 1600 rpm in 18th would be 98 mph.

The only downside to the 18 spd and 2.64 ratio is just as you mention... you are not going to jackrabbit start anything. It is not the best choice, by far, for P&D work. It is definately for road work and is more gradual process, but not so much that one can't get down a ramp and into traffic. And when very heavy, I may split the 3rd and 4th on the low side and then everything on top. I have only use granny low to start out once, and used it to do stuff like sliding tandems. Even with the tall rear ratio, it still has a lot of low end grunt. And surprisingly, reverse low is still very reasonable with tall rears. Am able to manuever very easily into any tight back and will not be racing. I really can't notice much difference from my old 13 and 3.42 rears when it comes to backing.

For a relative view of how gears and the rear match up, it is similar to a 18 or 13 tied to 3.55 rears, but with this you are one full gear lower at the same speed. Road speed is virtually identical at 65 at almost the same rpm with a 13 or 18 in the top hole with 3.55, and my 18 in 16th (or a 13 in 11th) with the 2.64's. I suppose a 13 would do fine for the most part in this setup, but the addition of the splits on the bottom with the 18 give a comfortable edge.

 

Do you think it would be similar if say I bought a different truck than you and specd it with the same gears and an 18? Id love to see the mpg's you could get out of a t660 or even a 389 with those specs.

Ethan

 

I would actually enjoy driving a truck set up like that. Most guys in road tractors with 18's never split the low side defeating the whole purpose of having one. Unecessary extra weight and expense - a 13 is all they need. I enjoy rowing through gears and never skip anything, unless downshifting. Heck I even start off in granny low every time, second when bobtailing. I've always took my time getting up to speed so the tradeoff in takeoff power - I'd likely never even notice that.

 

Whether it would be identical is up for grabs, but the concept of running in direct drive 16th (or 11th on a 13 spd) at road speed as being more efficient and the tranny running cooler is right on. Eaton's senior engineer thinks so, and I can confirm what he was putting out. I can see no reason that any other truck it wouldn't be a good combination. But only for regular OTR type of work. Those with special situations and such are going to have to avoid this. It is is not a great combination for heavy work or if you are hauling toothpicks out of the woods and corn out of the fields, or other goofy situations. This is strictly for normal OTR type of running. The 2.64's would equate well to those engines that like doing their best work in the 1350 - 1500 range, but for those engines that do better at lower rpms, like Cat C-15's, then even going taller to say, 2.47 is what is called for. Last I checked, that is all the taller you can go with a 40,000 dual axle. With something like a T660, 389, or Cascadia should be able to pop off with some impressive mpg numbers with the same setup as mine. Just because mine is all driven by a pre-egr engine doesn't mean that one of the newer engines that are doing good mpg figures wouldn't do even better.

But there is a middle ground here also.... something like a 3.08 rear ratio. It would put one in the first overdrive (.86) at road speed, but that is still more efficient than going double over (.73). Double over is just plain not going to be as efficient as direct or single over. It might be necessary to have a set up that requires double over, but 90% of what passes for trucking can live without double over or even single over. For those that have a little more demanding application that typical OTR stuff, might benefit with this middle ground ratio.

Something else about my setup, I am using new Meritor 14x axles back there. They have a premium amboid gears instead of standard hypoid gears. That could also be contributing somewhat to the increased efficiency. That is up for grabs.

 

Sounds good to me, I pull flats and my average gross is always between 70-80k lbs. Since I started flats back in June I've only hauled two loads under 70k gross.

So maybe running almost at gross all the time may not be the best option with those gears?

I don't run the mountains much, if I do its east of the Mississippi

Ethan

 

Well, like I stated earlier, Ethan, I had no issues grossing 80K and working two lane, hilly roads. It is your call. I know that when on the super slab 4 lanes and in hills, with even a gross load, it does extremely well. Much better than I would have thought. This whole concept is really "out there' compared to what most folks are doing for specs. I wondered, time and again, if I wasn't going to be crying in my beer over what I had done. But I would have it no other way, now that I have actual experience with it. For anyone else, they will have to figure out what their comfort level is in doing something like this. It violates everything we all have learned over the years about specs. It is hard to try something different. For sure, no fleet is going to try this with their trucks. This will always be an individual thing. And no OEM is going to suggest this combination. They are just as stuck in their ways as most drivers and fleets are. Nothing wrong with that. It just is what it is. I know my dealer was wondering what I had been smoking when I spec'd this truck this way. Now he is a believer, but I doubt he will suggest it to someone. He just won't go into a brain cramp now if someone wants to do this.

Unless someone is willing to go out on a limb, then they might be more at ease if they use traditional specs. I was out to make the most efficient truck I could and still do everything that I do. It worked. I like it. But, I could have been really up a creek without a paddle if it didn't work out. I sure would have hated to shell out to put shorter gears into the rears. But I took a shot.

Great signature pic, Ethan!

 

Thanks for the info, I've always wanted an 18 speed too lol. I'm sure that setup would be great, pre egr 12.7 Detroit, 18 speed, the gears you chose all in a Pete 389 glider flat top Woohoo! Lol

Ethan

 

One thing that can be amusing, when running 62-65 mph, is when someone chimes in on the CB with something like, "is that all the faster that truck will go", it can be fun to hear the response when you say "I am not even in the top hole yet, I still have two to go".

 

Schneider has been running 2:64's with direct 10's for years. Wal-Mart does it, Rhoel and some of the other megas. It's nothing new mostly like you say - very difficult concept to grasp flying in the face of logic. You do not want those specs in an ex-fleet truck with a 10 speed and 400 hp in hills always heard they fell flat on their face. But I've never driven one so don't know. The most difficult part for me to grasp is say pulling a grade like Monteagle at 80k or even running 81 in VA grossed out. I know you're saying it works but still it is hard to imagine. There are more and more specing this way..

 

I think our new flatbed trucks are geared different than the van trucks since all we haul is heavy stuff.

For instance when I had a Columbia in van division id run 10th gear, 63mph, @1450rpm and it would die on hills. Even small ones. On monteagle id have to get into 6th grossed out.

Now my flatbed truck prostar runs in 10th at 63mph at 1325rpm, and pulls hills like a champ though. Grossed out I run 8th gear up monteagle but because the Jake is crappy I have to run 7th going down the east bound side to keep from going over 35mph. My Detroit would go down in 8th and never touch 45mph with the jakes on grossed out.


If I could have the maxxforce with the Jake strength of my Detroit id be set.

Ethan