4000 gallon mack water truck on 40% grade

[gio400]

Goodnight how will a Mack e7 400 with 8ll and 6.14 diff carrying 4000 gallon of water perform on hills 30-40% grade. Will turning off be good with 6.14 ratio

[gio400]

The hills is between 20-30% grade steep

[JoeH]

How fast do you want to get up that hill? You just set it in low low and keep the engine revved up, you'll get to the top eventually.

[BOBWhite]

Doesn't sound like all that much especially with 400 horse and 6.14 ratio. 32,000lbs of water plus whatever trailer is being used should be a cake walk, although liquid transport is tricky on any sort of grade. 

[gio400]

How will do in a stop and start situation?

[JoeH]

Depends how good you are with a clutch.

What year is the truck? The vmac III engines the computer will assist by maintaining idle as a minimum.

On a hill from a dead stop, you have one foot on clutch, one on brake.   Use lowest gear you have, which on an 8LL is LL. Ease the clutch out til you feel it make contact and start to grab just enough to hold truck from rolling backwards, then your brake foot moves to accel pedal and gives it an extra couple hundred rpms at most while your left foot eases the clutch out the rest of the way.

[67RModel]

I foresee lots of driveline abuse and broken axle shafts or universal joints. Do you understand how steep a 30% grade is? A lot of people would struggle to walk up a 30% grade. Canton Avenue in Pittsburgh is often cited officially and unofficially as the steepest public street in North America at 37% grade. I have driven up and down it in a Honda car and it was scary quite frankly. Plus the top 2/3 are made of brick. Technically your not allowed to drive down it only up. I could not imagine driving up that hill in a truck loaded with 4000 gallons of water. Let alone stopping a 4000 gallon tanker on that hill and trying to get started again. If you did you would never shift out of Low gear until you reached the top. Forget 400hp. What you need is lots of gear reduction preferably planetary reductions at the wheel ends. Are the axles in the truck Mack top loader double reduction or conventional Meritor axles? I honestly would be worried about starving the engine for oil at such an extreme angle. I'm not familiar with where the oil pickup(s) are on these trucks but depending on where it is you might be sucking wind either going up or down. 

https://en.wikipedia.org/wiki/Canton_Avenue#:~:text=Canton Avenue is a street,street in the United States.&text=Canton Avenue is 630 ft,feet (6.4 m) long.

 

[gio400]

5 hours ago, JoeH said:

Depends how good you are with a clutch.

What year is the truck? The vmac III engines the computer will assist by maintaining idle as a minimum.

On a hill from a dead stop, you have one foot on clutch, one on brake.   Use lowest gear you have, which on an 8LL is LL. Ease the clutch out til you feel it make contact and start to grab just enough to hold truck from rolling backwards, then your brake foot moves to accel pedal and gives it an extra couple hundred rpms at most while your left foot eases the clutch out the rest of the way.

Truck is a 2001 with etech 400

[gio400]

5 hours ago, 67RModel said:

I foresee lots of driveline abuse and broken axle shafts or universal joints. Do you understand how steep a 30% grade is? A lot of people would struggle to walk up a 30% grade. Canton Avenue in Pittsburgh is often cited officially and unofficially as the steepest public street in North America at 37% grade. I have driven up and down it in a Honda car and it was scary quite frankly. Plus the top 2/3 are made of brick. Technically your not allowed to drive down it only up. I could not imagine driving up that hill in a truck loaded with 4000 gallons of water. Let alone stopping a 4000 gallon tanker on that hill and trying to get started again. If you did you would never shift out of Low gear until you reached the top. Forget 400hp. What you need is lots of gear reduction preferably planetary reductions at the wheel ends. Are the axles in the truck Mack top loader double reduction or conventional Meritor axles? I honestly would be worried about starving the engine for oil at such an extreme angle. I'm not familiar with where the oil pickup(s) are on these trucks but depending on where it is you might be sucking wind either going up or down. 

https://en.wikipedia.org/wiki/Canton_Avenue#:~:text=Canton Avenue is a street,street in the United States.&text=Canton Avenue is 630 ft,feet (6.4 m) long.

 

44 meritor axles with 6.14 ratio

[gio400]

8 minutes ago, gio400 said:

44 meritor axles with 6.14 ratio

What’s the difference with Mack top loader vs meritor axles if they had the same differential ratio

[67RModel]

Mack top loader axles are a double reduction design. Basically the torque multiplication is done in two steps rather than one. Much less strain on components and less of a chance to break things. Much more desirable for what you are attempting to do.

[gio400]

55 minutes ago, 67RModel said:

Mack top loader axles are a double reduction design. Basically the torque multiplication is done in two steps rather than one. Much less strain on components and less of a chance to break things. Much more desirable for what you are attempting to do.

With 8ll and 6.14 ratio will give me 89.39  %reduction in ll and in ll reverse 93.45 % wouldn’t that be good

[67RModel]

I can't say I know. I just know what a true 30-40% grade looks like and I would in no way whatsoever be wanting to be repeatedly starting and stopping on it loaded down with any amount of weight. I imagine you could get by with that setup for a while or a couple times but I don't think it will hold up long term. 30-40% grade is astronomically steep and I seriously doubt your setup was "designed" for that amount of driveline strain. Another thing to think about is what type of road surface will this be. There is a big difference if its soft soil versus an improved hard surface. And like I said earlier I would be concerned about starving the engine of oil depending on which way you are facing and how long you would be in that position. I'm sure its published somewhere the maximum recommended grade or angle its safe to operate one of these engines. Ideally I would think you would want some variety of Allison automatic and planetary reduction drive axles but that is beside the point. Only one way to find out....

[JoeH]

What's the application? Tell us more about these 30-40% grades. considering 45% is halfway to straight up, I have to question the accuracy of the grades.  Is this once in a while to come out of the pit at a quarry?

[Geoff Weeks]

Most have already made most of the important points. To outfit a truck to do 40% grade with that load, would make it useless for other tasks. Meritor planitary hub rear axles with a deep primary reduction at the differential and then calculate the needed transmission reduction.

 Torque hubs put the final reduction at the hubs, the axle shafts will not see the full torque required, as would be with any conventional diff, of either single or double reduction.

[Vladislav]

33 minutes ago, JoeH said:

What's the application? Tell us more about these 30-40% grades. considering 45% is halfway to straight up, I have to question the accuracy of the grades.  Is this once in a while to come out of the pit at a quarry?

A half way to straight up is 100%. Or 45 degree. 45% means elevation of 45 feet (or meter) achieved by passing 100 feet (or meter) horizontally. You drive 100 feet and get 45 feet higher.

Anyway 30-40% grade is an extreme figure for a road vehicle. And if the pavement would turn out slicky no way to hold the rig either with gas/clutch or brakes.

[Mark T]

One thing no one seems to give any mention to here, even if the amount of grade is half (still too much for a loaded truck that isn't application specific) When this thing ends up going backwards, there's not going to be any stopping it.   No foundation brakes are ever gonna hold this thing still going backwards .  (lol)  buy a pump and some pipes .