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leegsr52

Need help selecting transmission for new Granite

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I don't disagree with Superdogs logic. 1550 isn't way high and based on your application, slightly higher than typical may just work a bit better

From talking to a couple dealers (Nashville and Knoxville TN) it seems they make no distinction anymore between vocational and highway specs. All the guys I have talked to keep repeating is economy and fuel mileage,they don't seem to get the average speed or off highway aspect of dump truck work. I agree 4.19 rears are lower than the road gears in the high 3's but they are still specing a truck based on engine rpm @ highway speed for fuel mileage. I did a little quick math to get some low gear numbers for off road use with one salesman and he actually seemed surprised I was more interested in low speed off road use than highway cruise speed. I had to explain to the guy that I would run the interstate to get to the job, or part time in between but would spend over 80% of my time under 55mph. I also can't understand why when I call a dealer to ask about a dump truck or chassis for sale they don't have the light weight available, its a truck your going to use to haul by the ton weight is key. I guess I don't understand the "NEW" truck sales tactics, maybe if I was running 300 trucks and wanted maximum fuel economy.

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When specing a vocational truck trans first things on my list would be startability and gradability as fuel mileage will not help you out sitting there with a twisted driveshaft or u-joint broken. I personally think most salespeople are worried about the engine sweet spot for fuel mileage and RPM.Vocational trucks are a whole different world. Just my 2cents. Joe D.

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We had salesmen telling us to spec our log trucks with 3.91 gears, even one reccomended 3.73 or 3.55 . We told them no, we ordered 4.30. Its crazy to put road gears in a vocational on/off road truck, but the salesman don't understand the diference.

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You don't factor fuel economy on a dump truck.

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The whole discussion about fuel economy in my business is a total waste of time. When we get to a job, we sit there, running at 1250 rpm mixing concrete, anywhere from half an hour to two hours. How's that doing for your fuel economy?? So running at a little higher rpm on the highway isn't the end of the world. Matter of fact, I think I'm leaning more to the 4.8 ratio. The low end capability is more important to me than fuel mileage.

Another question I'd like to pose, and I know this is an engine and transmission topic, and not drivetrain, but for the sake of keeping the discussion of this truck in one place, I'll proceed. After calculating my max loaded weight, I end up with 47,000 lbs on the tandems. My original spec for rears was 46,000. Now the amount of time that I will actually be loaded to full 47,000 will be minimal, maybe a couple of times per week, if that. But being as this is a new truck that will probably be around for 25+ years, I'm thinking on upgrading to 52k rears @ an added cost of approx. $1600. Seems like a cheap investment for peace of mind and longevity. Anyone?

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what about your tag axle? or are you just running a tandem? whats the total gross weight? steer axle rating 20k?

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This is great information but its clear you have never driven either in actual use, I can tell you that there is no slipping an AMT to get very slow speed operation needed during paving and milling operations, the clutch is engaged and out and engaged and out and it is not smooth enough to stay in front of a milling machine unless you spec it with gears low enough to get the clutch fully engaged by 1 mph and keep it there, then you have no top end. The Allison has no clutch and therefore can be used from 0-top end speed very smoothly and there is also no clutch change needed every couple years as with every AMT I have ever heard of. The Allison keeps smooth power on the drive tires off road in rough terrain and loose materials where the AMT or Manual transmission ends up with driveline slack and shock loads. I agree AMT transmissions are the future for on road applications but Vocational trucks are just not suited to them and so far everyone I have heard of trying one hated it in slow speed operation, that same slow speed operation is where the Allison shines and I have never seen one get hot during slow speed operation, probably because you are not using enough throttle to heat it up.

I actually have a great deal of experience with both the Eaton AMTs and Allison in actual use. But we won't go there.

Anyone who disliked AMTs in low speed operation is probably thinking about the earlier (on-highway) UltraShift DM3 that used a centrifugal type clutch which engaged via engine speed. MUCH has changed since then.

First, the latest Eaton UltraShift Plus AMTs uses an electric clutch actuator which now allows the clutch to engage at idle, which significantly improves low speed operation. The original UltraShift DM3 and the current UltraShift Plus are two different animals (I fault Eaton for not creating an altogether new name for the current product to avoid confusion).

Second, Eaton now has an entire range of purpose-designed AMTs specifically for the vocational segment.

http://www.eaton.com/ecm/groups/public/@pub/@eaton/@roadranger/documents/content/ct_243345.pdf

You said something to the effect that if the clutch is constantly engaging and disengaging, then it is not smooth enough to stay in front of a milling machine unless you spec it with gears low enough to get the clutch fully engaged by 1 mph and keep it there, then you have no top end.

For that scenario, Eaton offers the 11-speed VMS spec AMT (paving, ect.) with a 26.08 first gear. That ratio, combined with the specialized vocational software and the electric clutch actuator, results in smooth low speed operation.

In reality, Eaton's vocational AMTs geared correctly will not engage and disengage the clutch. The driver selects the gear he wants and holds that gear. This disables upshifts and the clutch is engaged for slow speed curbing.

Another advantage of Eaton's vocational AMTs is the ratios available to creep at various speeds by selecting any gear. Allison has such few gears, the driver has little choice. Eaton is winning vocational business from Allison every day because of the UltraShift Plus AMT's slow speed maneuverability. The Allison's "urge to move” makes it harder to control the vehicle, while the Eaton AMT has no such problem.

And, having a 0.73 overdrive top gear, top end (speed) is in no way compromised. In fact, all Eaton vocational AMTs have a 0.73 or 0.74 top gear.

As for clutches, the precise electronic clutch engagement of Eaton's AMT transmissions consistently results in longer clutch life, not shorter.

Of course, different dump applications have varying requirements. And that's why Eaton offers 5 different vocational AMTs to ideally meet varying requirements. For example, I already mentioned the UltraShift Plus vocational 10 (VCS), 11 (VMS) and 13 speed (VHP) AMTs have 3 reverse gears, and the 18-speed (VXP) has 4 reverse gears.

Compared to the Allison, the vocational UltraShift Plus AMTs are significantly cheaper, will give you a simpler installation with better chassis integration, and deliver lower maintenance costs and better fuel economy. The Allison will definitely burn more fuel while sitting in torque converter mode, unable to lock the converter. While it may not become overheated, it is still wasting energy.

When I spec a municipal transit bus or residential refuse chassis, vehicles in stop-and-go operations, I spec an Allison transmission. But with school buses, the Eaton UltraShift HV medium duty AMTs come out ahead of the Allison with lower initial purchase cost, lower cost of ownership and superior fuel economy.

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I recently spoke with a contractor friend of mine, who bought an RD 10 wheel dump with the Allison. He's not thrilled with it. He says you don't retain control enough over the truck when backing down steep slopes and such.

An advantage of Eaton's vocational AMTs is the ratios available to creep at various speeds by selecting any gear. Allison has so few gears, the driver has little choice and less control.

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The whole discussion about fuel economy in my business is a total waste of time. When we get to a job, we sit there, running at 1250 rpm mixing concrete, anywhere from half an hour to two hours. How's that doing for your fuel economy?? So running at a little higher rpm on the highway isn't the end of the world. Matter of fact, I think I'm leaning more to the 4.8 ratio. The low end capability is more important to me than fuel mileage.

Another question I'd like to pose, and I know this is an engine and transmission topic, and not drivetrain, but for the sake of keeping the discussion of this truck in one place, I'll proceed. After calculating my max loaded weight, I end up with 47,000 lbs on the tandems. My original spec for rears was 46,000. Now the amount of time that I will actually be loaded to full 47,000 will be minimal, maybe a couple of times per week, if that. But being as this is a new truck that will probably be around for 25+ years, I'm thinking on upgrading to 52k rears @ an added cost of approx. $1600. Seems like a cheap investment for peace of mind and longevity. Anyone?

52's.

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Just to give a little more info, I calculated the rpm at various speeds for both the 4.5 and 4.8 ratios. Here's the data:

4.5 Ratio 4.8 Ratio

50 mph - 1150 rpm 1227 rpm

55 mph - 1266 rpm 1350 rpm

60 mph - 1381 rpm 1472 rpm

65 mph - 1496 rpm 1596 rpm

70 mph - 1611 rpm 1718 rpm

On average, there's about 100 rpm difference in each gear between the ratios.

My current Mack RD with a 300 hp E6 and 10 speed transmission does 65 mph at 1550 rpm, in tenth gear. At that rpm, I often find myself downshifting a gear on the highways I travel, due to the usually commuter related traffic. So, I'm thinking that going to the 4.8 ratio is not going to kill my fuel mileage. There's only a 46 rpm difference between the two. I'm thinking the value of having a better low end will offset the slightly lower fuel mileage that I may see.

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Just to give a little more info, I calculated the rpm at various speeds for both the 4.5 and 4.8 ratios. Here's the data:

4.5 Ratio 4.8 Ratio

50 mph - 1150 rpm 1227 rpm

55 mph - 1266 rpm 1350 rpm

60 mph - 1381 rpm 1472 rpm

65 mph - 1496 rpm 1596 rpm

70 mph - 1611 rpm 1718 rpm

On average, there's about 100 rpm difference in each gear between the ratios.

My current Mack RD with a 300 hp E6 and 10 speed transmission does 65 mph at 1550 rpm, in tenth gear. At that rpm, I often find myself downshifting a gear on the highways I travel, due to the usually commuter related traffic. So, I'm thinking that going to the 4.8 ratio is not going to kill my fuel mileage. There's only a 46 rpm difference between the two. I'm thinking the value of having a better low end will offset the slightly lower fuel mileage that I may see.

I doubt you will see any difference in fuel mileage.

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Just to give a little more info, I calculated the rpm at various speeds for both the 4.5 and 4.8 ratios. Here's the data:

4.5 Ratio 4.8 Ratio

50 mph - 1150 rpm 1227 rpm

55 mph - 1266 rpm 1350 rpm

60 mph - 1381 rpm 1472 rpm

65 mph - 1496 rpm 1596 rpm

70 mph - 1611 rpm 1718 rpm

On average, there's about 100 rpm difference in each gear between the ratios.

My current Mack RD with a 300 hp E6 and 10 speed transmission does 65 mph at 1550 rpm, in tenth gear. At that rpm, I often find myself downshifting a gear on the highways I travel, due to the usually commuter related traffic. So, I'm thinking that going to the 4.8 ratio is not going to kill my fuel mileage. There's only a 46 rpm difference between the two. I'm thinking the value of having a better low end will offset the slightly lower fuel mileage that I may see.

Rather then settling on a compromise spec with the ratio-limited Allison, you can have the best of both worlds in low end and high end with Eaton's vocational AMTs.

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