Need help selecting transmission for new Granite

[leegsr52]

How much of a weight difference we talking?

What's the recommended axle ratio with the Allison for on/off road applications?

[leegsr52]

1. The thing i've heard from guys who use these for construction, is that you don't have the control backing uphill and downhill when you're offsite. You can't hold the truck back like you can with a standard. I'm sure once I find out what the added cost is for the 2 speed reverse, i'll probably sing a different tune. LOL

[rsb502]

The 4500 weighs in at 893 with a pto, and 968 with a pto and retarder, the 4700 weighs 1149 with a pto and 1224 wth pto and retarder, the 4700 is 10" longer and 3 quarts more oil capacity also. I have never seen a truck with the 7 speed, all the garbage trucks, buses, fire trucks, concrete trucks and dump trucks I have been around were 5 or 6 speeds. I was looking at the gearing talking with mighty fruit about this check out his post on understanding specs in drivetrain it has road speed versus rpm for different rear gear ratios and tires sizes posted with the 4500 series. I have the rugged duty series brochure right here, the 4500 series has a 4.70 low gear and a .67OD, the 4700 has a 7.63 manually selected low gear but a 3.51 low for automatic use so when driving around the lowest gear you would have is higher than the 4500 series without stopping and selecting the low gear every time, the .64 OD doesn't really offer much difference from the .67 OD in the 4500, the rpm versus road speed would be like 30rpm difference with 11r22.5 tires. your 4700 series low second reverse gear is only offered with torque limiting and your first three gears are also torque limited in the 4700 your max torque input of 1850# is only rated for gears 4-7, in the 4500 series its rated for 1850 in gears 2 -6.

[rsb502]

You have to hold the brake pedal to hold the truck back with an automatic and a lot of guys are used to selecting a lower gear and using the engine brake in low-low, an Allison with a retarder and an engine brake will hold pretty good I would think from the stuff I have driven.

[rsb502]

Really need more info to select a gear ratio, tire size, desired road speed what kind of rpm at that road speed? Select a gear based on top gear driving the torque converter will take care of the slow speed stuff unless you just go nuts and get a super high gear, most of the Allison Mack trucks I have seen are 5.02 to 4.42 rears with several using the MP8 coming with 4.64 rears lately and I would think that would be a great gear for them.

[leegsr52]

So. It appears that you can't get the 4700RDS in a Mack anyways, because there is some f***ed up agreement between Mack and Allison, that limits what versions that Mack can put in their chassis? I don't get that. Mack must not have enough market share to throw their weight around. You can get it in a Kenworth, but that's not gonna happen. Back to the drawing board.

[rsb502]

4700 is overkill, you still only have 6 forward 1 reverse gears to use auto. The low 1st and second reverse are manually selected and torque limited anyway.

[leegsr52]

So. Made trip to the dealer today, and tried out the allison and 18 speed. The more we look at it, I think the Allison is the way we're gonna go. We do a lot of city work in Boston and suburbs, and the ease of driving that Allison will make the job a whole lot easier. I also rode with a friend of mine that has a 2006 Mack triaxle with the Allison. The truck shifts real smooth, pulls the hills nicely, and has plenty of engine brake power to help slow it down. I was impressed.

Now I just need to narrow down the axle ratio. Superdog's recommendations make sense. Somewhere between 4.64 and 5.02 seems like a good range. We go in a limited radius for our work. Probably within a 30 mile radius we do 80% or more of our work. With 12R24.5 rubber, I think the taller gears will give me all the highway speed we need. I want to be able to cruise at 65 in the optimum rpm range, but still have the ability to ramp it up to 70-75 if we have a long run, without pushing the rpm limits.

[maxidyne237]

Come on put 12.00 R24's on it!

[BC Mack]

So. Made trip to the dealer today, and tried out the allison and 18 speed. The more we look at it, I think the Allison is the way we're gonna go. We do a lot of city work in Boston and suburbs, and the ease of driving that Allison will make the job a whole lot easier. I also rode with a friend of mine that has a 2006 Mack triaxle with the Allison. The truck shifts real smooth, pulls the hills nicely, and has plenty of engine brake power to help slow it down. I was impressed.

Now I just need to narrow down the axle ratio. Superdog's recommendations make sense. Somewhere between 4.64 and 5.02 seems like a good range. We go in a limited radius for our work. Probably within a 30 mile radius we do 80% or more of our work. With 12R24.5 rubber, I think the taller gears will give me all the highway speed we need. I want to be able to cruise at 65 in the optimum rpm range, but still have the ability to ramp it up to 70-75 if we have a long run, without pushing the rpm limits.

All I can add to this this discussion is from the maintenance side... ask if it is possible to specify "Transynd" for the oil, or, change over to it on your first change. Talk to the Allison tech rep if you can and ask their opinion. Our fleet of 1200 buses with Allison, Voith and ZF trans all changed over 5 years ago from regular ATF and there has been a significant reduction in failures and overhaul time has increased, it works very well in our retarders with lowered temps...

BC Mack

[leegsr52]

Hey BC. Mack can only put the 4500RDS allison in their trucks due to an agreement with Allison. I'm not sure if you even get a retarder with the 4500RDS. I'll have to check. Would you recommend adding that option if available? Pros and Cons of having the additional retarder?

Is the Transynd an Allison synthetic oil?

Edited December 4, 2013 by Lee G

[rsb502]

4.64 rears, an Allison 4500RDS(.67OD) and 12R24.5 tires(45.6"diameter) makes for 1640rpm @ 70mph, I had 4.64 rears in my 04 Granite with a Mack 310M(.73OD) and 11R24.5 drives and that gave me 1800 @ 70 mph and it did great for me all over the middle TN area, the 4.19 rears Mack is pushing for Vocational trucks now seem high to me with an Allison, with the .67OD and 12R24.5 tires that would make for 1450 rpm @ 70 and for a truck that rarely gets there that's wasting a lot of gear where you need it down low. Good Luck with the truck and keep us informed on what you do.

[rsb502]

Yes a retarder is available with the 4500 series, I asked around today and from what I have been told nobody here has ever seen a 4700 series in any truck, according to my buddy at KW they are supposedly reserved for high horsepower heavy haul trucks all they sell in dump trucks is the 4500 series. Also from my Allison literature the 4500 is available with low,md and high capacity retarders and the 4700 is only available with medium, the 4700 series seems to be a very specialized transmission for specific applications only.

[leegsr52]

Just for info sake, for anyone looking at this. The MP8 Maxicruise has an operating range from 1200-1950 rpm. It has a maximum torque of 1660 lbft between 1100-1300 rpm. Max horsepower of 415 hp between 1500-1700 rpm . So with those numbers, along with 12R24.5 rubber, anyone got thoughts on axle ratios?

[RFCDrum]

I drove a granite with an 427, 6 speed Allison with transmision retarder 58 rears on 11r24 big rubber.

[leegsr52]

Thanks superdog! Have you had any experience with retarders on your own trucks? Would you recommend adding that option?

[leegsr52]

Hey RFC. Did you see any advantage to having a retarder, as well as the engine brake?

[BC Mack]

Hey BC. Mack can only put the 4500RDS allison in their trucks due to an agreement with Allison. I'm not sure if you even get a retarder with the 4500RDS. I'll have to check. Would you recommend adding that option if available? Pros and Cons of having the additional retarder?

Is the Transynd an Allison synthetic oil?

We use the older B400 and B500, plus the new 'hybrid' which is just an electric B400.... the transmission retarder has been in city buses nationwide for many years, there is also an electric 'Telma' unit for drivelines, heavy loads downhill are normal for us and recent trials for a new bus order study had buses loaded with sandbags disconnect the retarder for the test, most smoked the disc brakes at the bottom of the test hill, they actually had to tow the Orion away.

the retarder and trans cooler should be on your list "to be considered" if you plan to be loaded down long hills with these auto's..

we have the programming set for "throttle off" but "brake on" is available but driver feedback was complaints of sore legs on the second option as the retarder held the speed with throttle off and the occasional dab of the brakes. Certification for the bus is done with retarder off and IIRC it is for two full stops within a time period and I was told by our test engineer this is marginal in real life. Probably the same spec Mack has to meet for braking distance so the retarder may be seen as a back-up and not just a lining saver.

Transynd is synthetic... I think we pay $7 per litre in bulk but the 24,000km change for ATF is now 72,000km for Transynd, so the math is good.

HTH.... and sorry guys for using the 'bus' word so many times.. LOL

BC Mack

[rsb502]

The Mack spec sheet I have specifies Allison synthetic fluid and trans cooler from the factory in the 4500RDS, this seems to be a good spec sheet to build a Granite from, it has the MP7 405M, 4500 Allison 6 speed, Im still not sold on the M Ride 46k(Volvo T ride) rear suspension but it is spec'd in this truck and supposedly has a close to 4300# weight savings over 44K camelback, I would change some things to make it nicer for the driver, if it was mine to drive daily probably the Rawhide package, if not every available option for the interior and a full gauge package.

[rsb502]

send me your email in a pm and I will forward the spec sheet I have for a dump chassis, its set up for a 16' body and a tag axle to make a heavy tri axle.

[MackMann85]

the 4700 is not available due to the extra weight and the stresses that causes and is a very specialized application trans. any reference to an agreement being the issue is false.

the MP s ideal rpm for fuel economy is in the 1350-1450 range where the hp and trq curves roughly cross over. I would stay on the high side of that for cruise rpm, 1450-1550 with a cement truck not spending much highway time, maybe 1600. with this more modern engine you don't want to be cruising much above that at highway speed to reduce fuel use and NVH

[leegsr52]

I did some digging on line, and came up with the formula that is used for computing gear ratios, mph, etc, by entering the known entities. Here it is:

engine rpm x 60 / transmission ratio / tire revs per mile / rear axle ratio = MPH

Using this formula, you can calculate for an unknown, if you know all the other components

Here are my fixed knowns:

12R24.5 tires - 458 revs per mile

Allison 6th gear ratio - .67

My three unknowns are engine rpm, rear axle ratio and MPH

What we are trying to determine is which axle ratio we should go with. The three ratios that Mack has available for the 46k rears, that are in the ballpark of what we might want are 4.19, 4.50 and 4.8

We do work in and around the Boston area. We are frequently on the main highways, 95, 93, 128 and 90 getting to our jobs. We don't travel for hours on end at 70+ mph to get to our jobs. We generally travel in a 25-30 mile radius If we don't hit traffic, our longest steady run is probably an hour, and even that is occasionally, not every day.

Realistically, we are in a lot of rush hour traffic, road work , etc, and so if I had to give an average high speed that we might reach, I would say between 60-65 would be the top end. And most times, we are probably under that. And highway driving is maybe 50% of our driving, with the rest being on back roads.

That said, I'm using 65 mph cruise speed in the above formula to come up with my calculations. Based on Mack Legacy's post above, and the Mack performance data for the MP8, I'm using 1550 engine rpm for my selected cruise speed.

Plug all that into the formula:

1550 engine rpm x 60 / .67 transmission ratio / 458 tire revs per mile / axle ratio = 65 mph

Rework the formula to get your unknown (axle ratio), and you get a 4.66 axle ratio

Substitute 1600 rpm in the formula, leaving everything else the same you come up with a 4.81 axle ratio

Now do the formula putting in the actual available ratios, leaving the 65 mph, and calculate the resulting rpm, and you get the following:

4.5 axle ratio @ 65 mph - 1496 rpm

4.8 axle ratio @ 65 mph - 1595 rpm

I think the 4.5 ratio may be the best pick. It puts the engine in its optimum fuel economy rpm range for 65 mph cruise speed.

Although, the 4.8 ratio is only 50 rpm outside the optimum fuel economy rpm range (1450-1550). It would give a little more torque on the low end for off road, and backing up grades.

At least I'm able to narrow it down to two ratios. Let me know your thoughts.

[RFCDrum]

Hey RFC. Did you see any advantage to having a retarder, as well as the engine brake?

Lee the Allison retarder I drove had a problem and worked good on the low rpms but didn't do shit at high speed. I also drove a Granite with an Allsion and it had a Jake and that worked pretty good. I also ran a Western Star with a 6 speed Allison that had a 3 stage Pac Brake on a Series 60 Detroit which worked good. I still think the two combined would be a great combo.

[rsb502]

I'd run the 4.80 with a 12R24.5 tire, 4.50 with an 11R22.5, that puts you right around 1550@65mph which is perfect for torque and pulling hills. Lots of talk about economy and fuel mileage gets thrown around with truck dealers now and for a highway truck it pays off in the long run. However in a heavy haul,on/off road truck a higher gear is killing your bottom end which is where the truck will spend 75-85% of its life. Its really up to you, you have all the information so I'd say you are a well informed buyer, you have to figure your average speed and work from there. For a dump truck that is going to run off road hauling dirt and rock low gears are key to keep drive line stress to a minimum and keep the truck moving on extreme grades and in soft ground. For a dump truck like say a quad purchased to stockpile a concrete or asphalt plant the truck will spend more of its life on the road and can benefit from 4.19 gears for fuel economy. I would have to go with the numerically higher gears above for the work you have planned, like I said all the dump trucks I've ever run were 4.42 or 4.64 rears with 11R24.5 drives and the 4.42 trucks could have been geared steeper at times with the manual transmission where the Allison would have done ok due to the torque converter.

[MackMann85]

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