Axle ratios

[luvrbus]

According to his serial number he has a good engine that can be upgraded for more power  W=12.7L  K= DDEC 111 or lV  B= premium built engine  28= bus engine 1991 or later FWIW 

[wildbob24]

Something else to consider when you're going 80mph is your tires are rated for a maximum speed of 75.

Bob

[eagle19952]

I'm not going to do 80 mph all the time, only when it is legal and I deem it safe in my best judgment to do so. I want the ability to go 80 mph.

The vehicle weight is 35,100 lb, GVWR 48,000 lb. I don't tow and I don't have slides. Tires are 315/80R22.5, diameter 42.3". Engine is a Detroit Diesel 6067BK28 12.7L rated at 430hp. I understand fuel economy will be poor at high speeds, but I'm looking to save whatever fuel I can. Again, I usually only run flat routes.

save your 80 for 1%-2% grades...down hill..
But, do tell, where is 80 mph in a bus legal ?

[Swadian]

save your 80 for 1%-2% grades...down hill..
But, do tell, where is 80 mph in a bus legal ?

In Nevada, South Dakota, and possibly Utah and Wyoming.

Usually, I'm at 75 mph; again, I would rarely actually go 80 mph. However, I'd like to save fuel at both 75 and 80.

[luvrbus]

save your 80 for 1%-2% grades...down hill..
But, do tell, where is 80 mph in a bus legal ?

From El Paso to Junction Tx on I 10 some of the turn pikes are 85 mph and they do run the speed limit it's scary to have a 50,000 bus pass you loaded with tourist when you are driving 70 to 75 mph  

[luvrbus]

Hum I think this is the guy with Wang that is starting a bus line to run between Phoenix and Reno not for sure.I did see a gofund account for a start up bus line there in May ,he has a bus blog also if it is same guy real passionate about buses and bus travel.

[TomC]

Only occasional 80mph, I would gear with 3.90. 315/80-R22.5 are also 485rpm tires (overall diameter and rolling diameter are different). Then with 1450lb/ft torque and figure 40,000lbs (for future stuff) you'll be fine.
Startability is figured- first take your maximum weight and multiply it by 10.7 and put that into memory. Then take your maximum engine torque (on a manual would be your clutch engagement torque) 1450 multiply by first gear 3.51 multiply by torque converter ratio-which for a 1450 torque engine would be 1.62 (2450 maximum torque converter divided by engine torque) multiply by rear ratio of 3.9, multiply by tire rotation of 485 then divide by the memory weight factor and you'll get 36.4% startability! (Freightliner figured 22% startability for off road trucks and at least 18% startability for on road trucks). You'll have no problems. Good Luck, TomC

[luvrbus]

Allison won't approve 3:90 for a B500 he will need a outlaw to reprogram it because Allison will lock out 6th gear with that ratio for lubrication purposes if he goes there

[AdamWalkup]

I have a 99 DL3 with 12.7, and gear was changed to 3.73.  It works great, no problems starting, changes to 6th gear at about 65 mph.  It gets great mileage on the highway, and is our first coach out for long out of state trips, often running Biloxi trips from our bus shop in south Florida on a weekly basis.

Interestingly the actual in the field fuel mileage is not THAT much better, I see larger variances between different buses.  On a standard coach with a 4.30 ratio, we average about 6.5 mpg on the highway, where this bus will get 6.8-7.5 regularly.  What I do notice is that the weight will change the mileage more on this bus, when running light it gets MUCH better mileage, but on a trip loaded with people and LOTS of luggage, the mileage won't be much better.

The bus seems overall very happy with this set up, and I may change some more of them.  It brings the shift point to a higher speed, but the engine tranny seem happy, they just think they are running slower road speed then they really are.  When mountain climbing it just down shifts earlier, but is very happy climbing in 5th, or even 4th.

[Swadian]

Hum I think this is the guy with Wang that is starting a bus line to run between Phoenix and Reno not for sure.I did see a gofund account for a start up bus line there in May ,he has a bus blog also if it is same guy real passionate about buses and bus travel.

Mr. Wang is my friend. He's the one looking to buy a bus from Charlotte, but he can't find a mechanic to inspect it.

I have a 99 DL3 with 12.7, and gear was changed to 3.73.  It works great, no problems starting, changes to 6th gear at about 65 mph.  It gets great mileage on the highway, and is our first coach out for long out of state trips, often running Biloxi trips from our bus shop in south Florida on a weekly basis.

Interestingly the actual in the field fuel mileage is not THAT much better, I see larger variances between different buses.  On a standard coach with a 4.30 ratio, we average about 6.5 mpg on the highway, where this bus will get 6.8-7.5 regularly.  What I do notice is that the weight will change the mileage more on this bus, when running light it gets MUCH better mileage, but on a trip loaded with people and LOTS of luggage, the mileage won't be much better.

The bus seems overall very happy with this set up, and I may change some more of them.  It brings the shift point to a higher speed, but the engine tranny seem happy, they just think they are running slower road speed then they really are.  When mountain climbing it just down shifts earlier, but is very happy climbing in 5th, or even 4th.

Considering this, I think I'm gonna replace the current 4.30 with a 3.73. Prevost had a demo X3-45 with 3.58. I'm not sure if I can go much higher (lower numerically) than 3.73 with this particular unit. I'd go all the way to 3.21 if I could.

[AdamWalkup]

you can go to 3.21, I have a 3.21 unit on the floor in our shop, and a friend has a 99 DL that was changed to 3.21.  That ratio is way to high, and will hunt for 6th all the time, not only is it hard on the transmission, it is obnoxious for the riders feeling it shift on every overpass.  With our 3.73 I think we are turning about 1350 at 70mph, which is close to perfect.

[luvrbus]

That Prevost he is talking about has a D13 Volvo engine 1100 rpm peak torque the most popular ratio is 3:58 to 3:91 for that bus around here in AZ with the generation V World 4000 transmission they don't hunt because the generation V controls the engine.
The ones with the 12 speed I shift use a 2:50 gear.I plan on using the Allison 10 speed if fuel goes back to 4 bucks a gal I already have the 10 speed Allison.From all the info I can find the 12.7 will yield you better fuel mileage set @ 510 hp so that is where I am at and will see if not back to 470 hp  

[Swadian]

Can I update the transmission to the latest Gen V to go to a higher gear without hunting?

Also, can I go any higher than 3.73 with the existing gear ratio without hunting?

[luvrbus]

I have no idea but you would need the lasted electronics on the engine,this is conversion RV board most of us are loaded and towing a trailer or vehicle traveling around 60 to 65 mph and you are a charter bus running as fast as you can from point A to B huge difference for revenue that I understand.I know 3:73 gears in a RV at the speeds we drive it will drive you nuts hunting between 5th and 6th gears BTDT

[AdamWalkup]

I agree, I run the 3.73 in one of our charter buses, because they cruise 95% of the time with cruise set on 70mph.  In my motorhome I'm happy with the standard 4.30, since I tend to run a little slower, and the bus is so heavy, and I often have a 10K trailer behind.  I would also not use the 3.73 if I was in a mountain area, but it does work wonderful on the flat lands of the south, in charter operations.