Questions on Considering re-gearing for better fuel mileage

[petehall12]

I Currently have a 2004 cv713 quad dump truck the truck never totes over 70000 pounds. The motor is a  Ami. 370 a t310MLR trans, 4.64 gears and 24.5 tires.  Truck currently runs at 1475-1500 rpms at 55 mph averaging 6 mpg. Considering gearing higher to bring my rpms down to somewhere around 1275-1300 at 55mph. Not to concerned  about power but just wanting better fuel efficiency.  But not sure if the motors power curve can handle that. 

[BOBWhite]

Is the motor stock? If the stock restrictor manifold is still on that's what's holding your MPG back the most. Here is a great post describing the whole process of Souping up one of these motors:

I think some people on here have done re-gears on Mack axles but I'm not sure the on process (if you have Mack axles).  

[mrsmackpaul]

That I think would have to be the most detailed thread on here to follow on this type of thing

 

Paul

[petehall12]

4 hours ago, BOBWhite said:

Is the motor stock? If the stock restrictor manifold is still on that's what's holding your MPG back the most. Here is a great post describing the whole process of Souping up one of these motors:

I think some people on here have done re-gears on Mack axles but I'm not sure the on process (if you have Mack axles).  

Yeah it’s a stock Mack with mack rears. I have read through that and that project is in the works maybe not the injectors right now.  but definitely helping my dog breathe better. But only having that 10 speed keeps my rpms so high with those 4.64 gears. Wasn’t sure how much of an improvement I will get just by fixinig  the exhaust side. 

[The Heinz]

6 hours ago, BOBWhite said:

I think some people on here have done re-gears on Mack axles but I'm not sure the on process (if you have Mack axles).  

We have a customer with a somewhat new to them 2000 RD690 that wanted similar, so I was told to get a quote for different ratio diffs. We ARE a dealership after all, much cheaper in the long run to swap diffs thanks to labor rates. I'd assume you could find some diffs on a wrecked truck for cheap and clean them up before install as a money/time saver. 

[Geoff Weeks]

Only thing I'd add is DO YOUR HOMEWORK! don't guess, look at BSFC figures and base your desired operating speed to match that, realize often a small change makes big a difference, that is both good and bad, as if you are close but not right where you need to be, it could be a wasted effort.

 I did my Marmon and gained 3/4 to 1 MPG in my operation. I was mostly on hiway 65MPH and could make my selection based on that. I had a 15 spd Eaton that could handle the low end, but went with 2 spd rears anyway.

 I did a full spreadsheet, looking at starting ratio, and what it would do to hill climbing power, where the engine would be at differing speeds in all gears.

 When I did the swap, everything was where the math said it would be, made a much more "driveable" truck for my use. That said, I have heard from many that made swaps based on "what someone else said would be better" or a seat of the pants "guess" and were unhappy (not surprisingly) with the outcome.

 Your truck and engine are new enough you should be able to get the BSFC graphs, you need to really log your usage and look at all you need it to do, starting in soft ground etc. before making a choice. It may take more gears in the trans to make use of the gears in the back to their best.

 If you just slow it down in the rear, you may have trouble getting out of soft ground loaded.  It is a whole system, and needs to be looked at that way. In my opinion, 10 spds have too much ratio gaps, but I was working on older, mechanical engines, designed for many ratio transmissions (13 or more gears). Still the starting ability on soft ground is still something you need to keep in mind.

[petehall12]

1 hour ago, The Heinz said:

We have a customer with a somewhat new to them 2000 RD690 that wanted similar, so I was told to get a quote for different ratio diffs. We ARE a dealership after all, much cheaper in the long run to swap diffs thanks to labor rates. I'd assume you could find some diffs on a wrecked truck for cheap and clean them up before install as a money/time saver. 

Yeah my question is how high of gear do I need to go to and hopefully an estimate on the improvements in the MPG. 

[Geoff Weeks]

32 minutes ago, petehall12 said:

Yeah my question is how high of gear do I need to go to and hopefully an estimate on the improvements in the MPG. 

Homework grade F!

No one can answer that question without knowing how and where the truck is operating. the roads (or lack of them) and the loading and unloading under what conditions.

 You want simple answers and there aren't any. The mfg chose the ratio the truck came with, to fit the widest range of operation. That was a guess, if you want to optimize for your operation you HAVE to do the math and plot it out.

 If you are not willing or able to do so, save your money you would spend on a ratio change and put it into fuel, it will be the best bang for the buck.

Edited April 10 by Geoff Weeks

[petehall12]

1 hour ago, Geoff Weeks said:

Homework grade F!

No one can answer that question without knowing how and where the truck is operating. the roads (or lack of them) and the loading and unloading under what conditions.

 You want simple answers and there aren't any. The mfg chose the ratio the truck came with, to fit the widest range of operation. That was a guess, if you want to optimize for your operation you HAVE to do the math and plot it out.

 If you are not willing or able to do so, save your money you would spend on a ratio change and put it into fuel, it will be the best bang for the buck.

I have been doing my homework “hence asking questions on here” and I have some ideas. But I I am a big advocate of asking other people as well to see what their experiences have been like. To further my knowledge and try to make the best informed decisions I can make. So I just don’t throw money at it hoping it works. 

Edited April 10 by petehall12

[BOBWhite]

You could even drop a few MPG by going with a higher rear gear! Your working each of those 12 Liters pretty hard even if your only hauling 70,000lbs! 

10 gears just isn't very much to play with, and like Geoff said getting out of the mud loaded is a big thing to consider. I would get some sort of fuel flow meter to see what RPM that motor wants to be at and do your ratio calculations off that. 

[petehall12]

34 minutes ago, BOBWhite said:

You could even drop a few MPG by going with a higher rear gear! Your working each of those 12 Liters pretty hard even if your only hauling 70,000lbs! 

10 gears just isn't very much to play with, and like Geoff said getting out of the mud loaded is a big thing to consider. I would get some sort of fuel flow meter to see what RPM that motor wants to be at and do your ratio calculations off that. 

Awnsers like this is what I am looking for.  This truck was specked for the hills of PA and I live on the coast of NC. So everything is fairly flat and I mostly haul asphalt and rock 98% of the time. I am very rarely in a sand mine. But if my conclusion is I need to leave it alone I am fine with that. But if there is improvements I can make I would like to you know what I mean

[Mark T]

I had one ( similar )  4.17s.  mine wasn't very good on fuel and it was terrible as far as drivability.

[Geoff Weeks]

This is exactly where the BSFC graphs come in. In the old days a good truck salesman did the calculations for each truck, working with the buyer and the available options from the mfg. That is what YOU need to do. If you don't understand it, you need someone who not only does, but knows EXACTLY how you are going to use it.

 Basing you choice off what someone here or somewhere else says worked for them, will far more likely put you in a worse position then you are now.

 Modern trucks are often made to to best compromise and not "spec built" like they were in the older days. It can be the best it can be, as new trucks can handle wider operation than the older mechanical truck could. So if there is any improvement to be made, you are going to have to optimize for your exact need, or even know that there is no change that will yield better results. The time to work this out is before you plunk down dollar one on any change, not after you tried something and found it didn't yield the improvement you had hoped for.

 Getting it wrong may mean a slight improvement on the hiway but will tear up clutches and drivelines  getting started, or may even give no advantage on the hiway and still tear up clutches and drivelines.

 That is why, as someone who has done it, I say do your homework! Been there done that and got the T shirt, I saw the results I saw exactly because it put the time in, and the results were exactly what the math predicted it would be.

 With modern electronic engines, they can do well in a broader range of RPM and load, so the answer you get may well be stay with what you have.

 I am not being obtuse or mean, I am giving you the experience of someone who actually has done it.  There are no shortcuts that will give good results.

[mechohaulic]

I'M REALLY LIKIEN  the part about "in the old days a good truck salesman did the calculations!! boy ain't that 110% right. can remember a salesman bringing a customer out to SEE and ROAD TEST  a unit. many were built for this terrain. today "one size fits all attitude" and "not spec built "LIKE THEY WERE IN THE OLDER DAYS ". and yes I agree with  Geoff.  seeing the $$ cost of things here , I would do a heck of a lot of calculating first.

[67RModel]

Its been a while since I drove an ASET AMI but as I recall they were very gutless in low rpms. Pretty respectable reliability for an early EGR engine but completely contrary to what Mack vocational engines had been since the 237 Maxidyne was made in 1965. The AMIs had zero lugging ability and seemed like they were derated below 1300 -1350 RPMs. The old mechanical E6 & E7 Maxidynes would keep pulling like a freight train down to 1100. These things were nothing like that. My guess is your current ratio is specd to keep the Revs where they are for a reason. I would not want an AMI 370 to cruise below 1300 or 1400 RPM. 

Edited April 10 by 67RModel

[mechohaulic]

and a freight train they were. when things went from 15/18/20 speed transmissions to a ( 5 ) FIVE  speed later to 6; you knew changes were on the horizon! BUT THOSE 5 and 6 speeds did the job ; even better in some cases. many old timers (not me then) said NO WAY a truck pulls down to 11/1200.  don't know about this ASET  AMI stuff, one indication glad I gave up my CDL. 

[petehall12]

1 hour ago, Geoff Weeks said:

This is exactly where the BSFC graphs come in. In the old days a good truck salesman did the calculations for each truck, working with the buyer and the available options from the mfg. That is what YOU need to do. If you don't understand it, you need someone who not only does, but knows EXACTLY how you are going to use it.

 Basing you choice off what someone here or somewhere else says worked for them, will far more likely put you in a worse position then you are now.

 Modern trucks are often made to to best compromise and not "spec built" like they were in the older days. It can be the best it can be, as new trucks can handle wider operation than the older mechanical truck could. So if there is any improvement to be made, you are going to have to optimize for your exact need, or even know that there is no change that will yield better results. The time to work this out is before you plunk down dollar one on any change, not after you tried something and found it didn't yield the improvement you had hoped for.

 Getting it wrong may mean a slight improvement on the hiway but will tear up clutches and drivelines  getting started, or may even give no advantage on the hiway and still tear up clutches and drivelines.

 That is why, as someone who has done it, I say do your homework! Been there done that and got the T shirt, I saw the results I saw exactly because it put the time in, and the results were exactly what the math predicted it would be.

 With modern electronic engines, they can do well in a broader range of RPM and load, so the answer you get may well be stay with what you have.

 I am not being obtuse or mean, I am giving you the experience of someone who actually has done it.  There are no shortcuts that will give good results.

No sir.  you are not being mean at all.  this is why ask questions because I am not a now it all. With out people giving responses like you have nobody learns anything even just telling somebody to use graphs and what things to account for helps. I understand there is no magic combination. That is why I ask questions and do my homework before I spend money. If I just spent money when ever an idea popped in my head with out doing this I would make a lot of stupid decisions. 

[mechohaulic]

wouldn't go extreme of saying " I would make a lot of stupid decisions ", may be more accurate in to days world of stating " I would make a lot of EXPENSIVE unnecessary decisions.

[petehall12]

59 minutes ago, mechohaulic said:

wouldn't go extreme of saying " I would make a lot of stupid decisions ", may be more accurate in to days world of stating " I would make a lot of EXPENSIVE unnecessary decisions.

Isn’t that truth

[The Heinz]

The customer I mentioned previously never actually went through with the diff swap, it just cost too much money and downtime just to get his RPM's and top highway speed to where he preferred. It's definitely doable especially if you do it yourself or have someone cheaper than a Mack dealer do it. I don't know which you'd rather do/have done: the "ASET delete" or the regear/diff swap. In my opinion, which doesn't hold much weight mind you, giving your engine the ability to breath would probably be the first thing I'd do if I were in your shoes. 

What I did to get the part numbers for the diffs was create an eService case. They usually suck, but specification questions like this do well with them. I have to have the entire VIN to start one if you wanted to go that route. I unfortunately don't have old books or knowledge on diff part numbers and their gear ratios! 

[petehall12]

2 hours ago, The Heinz said:

The customer I mentioned previously never actually went through with the diff swap, it just cost too much money and downtime just to get his RPM's and top highway speed to where he preferred. It's definitely doable especially if you do it yourself or have someone cheaper than a Mack dealer do it. I don't know which you'd rather do/have done: the "ASET delete" or the regear/diff swap. In my opinion, which doesn't hold much weight mind you, giving your engine the ability to breath would probably be the first thing I'd do if I were in your shoes. 

What I did to get the part numbers for the diffs was create an eService case. They usually suck, but specification questions like this do well with them. I have to have the entire VIN to start one if you wanted to go that route. I unfortunately don't have old books or knowledge on diff part numbers and their gear ratios! 

Yeah I am definitely going to make I breathe better don’t now much about the ASET delete but I am going to put a fleet air filter on it and upgrade the exhaust Mack technicians way with a older exhaust manifold. I just don’t now if spending $2000 on a polished one would be worth it

[Geoff Weeks]

My guess is the time and money will not be worth the trouble. I had about $3K total in my swap, but I did everything myself, and I already had a single axle parts truck with a 2 spd rear. I bought the front "core" and re ratioed both myself (purchased new ring and pinion for both). The housings in the truck would accept 2 spd in place of the singles with no change to the housings. I have the experience to replace gears and set-up a hypoid drive set.  All that was done over 10 years ago. Look at your return on money spent and include down time in the figures. 

 I doubt you could replace the rears like for like for that price. That is just for the "pigs" and no labor, using used "pigs".

 $3 grand pays for a lot of fuel.

[The Heinz]

4 hours ago, petehall12 said:

Yeah I am definitely going to make I breathe better don’t now much about the ASET delete but I am going to put a fleet air filter on it and upgrade the exhaust Mack technicians way with a older exhaust manifold. I just don’t now if spending $2000 on a polished one would be worth it

The guy that posted the original improved ASET upgrade mentioned getting one from a local scrapyard, given getting a brand new one from a dealer like me (and discounting the three pieces heavily) costs around $1k + shipping, I'd vote for the scrapyard route to save money. He also mentioned not needing to replace the cam, which seems logical; to my knowledge the internal EGR the cam performs is similar to the Cummins 24 valve common rail engines, which were extremely reliable. Someone correct me if I'm wrong though. 

[Mark T]

I've reread this many times. I had a '06 AMI 370  4.17s and a Fuller 9 speed (overgear is pretty close as your transmission).  I speced it to be light and aiming to get good fuel mileage. I can honestly say that was by far the worst truck I had ever purchased new.  It was terrible on fuel, and by terrible I mean in the low 70s (weight) you had to drive it likean old lady to get in the four miles per gallon range. The thing was like a turtle on it's back. There were spots on blacktop it had all it could do to get moving.  It was back to several dealers and on the dyno and .....  The truck was junk, and while a little worse than others , not night and day difference.  Like I said, I've read this over a couple times, and from your first post ?   I think I would leave it alone and keep doing what you're doing to it as far as operating it ( you're doing something right )  Those engines were filthy too, you go spending a bundle on reratioing it and next thing you know there's a hole in the block where a wrist pin let go.  Personally, I think it's a case of  "if it ain't broke.... don't fix it"   The gearing it faster for mileage might not work on this one without spending a fortune.

[Geoff Weeks]

Oh, and one thing I didn't mention but may be should have, when I did my swap, I went from 3.90's to 4.11'/ 5.63's, and my mileage went up. You can be too slow.