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Old 07-02-2016, 01:12 PM   #1
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Join Date: Apr 2013
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Engine: 5.9 Cummins, Allison 545
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weight and towing

happy holiday 4th of July weekend to all.

i went camping this week in the mountains and took my atv along for the trip. about half way there i stopped for fuel and they had a scale at the truck stop.

i haven't weighed since before the conversion so i was curious, and i was towing.

so the scale says -
front axle------------10,120
rear axle-------------11,280
tow axle---------------2,960
gross-----------------24,360

the tag on the bus says -
front axle-----------12,000
rear axle------------19,000
gross----------------25,800

so the front axle is at 84% of its weight rating and the rear axle is at 60% of its rating.

the bus still doesnt care for towing, it slows down the top speed a couple mph, and the mountain grades are slow (10-15 mph).

my bus has the cummins 5.9, at545, and a 4.7 rear. top speed is 67 or 64 towing.



fwiw
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Old 07-02-2016, 07:21 PM   #2
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Happy 4th, turf! Thanks for this info.

My brother's '95 Ram w/5.9l CDT & AT is only rated at 18k lb GCWR with the 4.10 rear. It is sluggish at full-load but fine once you get things moving. The interstates are not fun at all with more than a 16' runabout behind you (3k lbs max). We always feel we're in the way. Even the 18 wheelers pass us up hills and on flats.

My biggest complaint about skoolies is the totally inappropriate drivetrain for our purpose. Swaps are mega $$$ and beyond most good home mechanics. Skoolies generally require trade-offs and lowered expectations.


Quote:
Originally Posted by turf View Post
happy holiday 4th of July weekend to all.

i went camping this week in the mountains and took my atv along for the trip. about half way there i stopped for fuel and they had a scale at the truck stop.

i haven't weighed since before the conversion so i was curious, and i was towing.

so the scale says -
front axle------------10,120
rear axle-------------11,280
tow axle---------------2,960
gross-----------------24,360

the tag on the bus says -
front axle-----------12,000
rear axle------------19,000
gross----------------25,800

so the front axle is at 84% of its weight rating and the rear axle is at 60% of its rating.

the bus still doesnt care for towing, it slows down the top speed a couple mph, and the mountain grades are slow (10-15 mph).

my bus has the cummins 5.9, at545, and a 4.7 rear. top speed is 67 or 64 towing.



fwiw
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Old 07-02-2016, 07:56 PM   #3
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I had a 96 Ram, cranked up to about 400 hp, 5 speed. Put 260,000 miles in 2 years. Regularly grossed over 25,000 lbs. Would pull most mountains in 5th Gear witn cruise on. Averaged about 13 mpg.
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Old 07-02-2016, 08:57 PM   #4
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I had a 96 Ram, cranked up to about 400 hp, 5 speed. Put 260,000 miles in 2 years. Regularly grossed over 25,000 lbs. Would pull most mountains in 5th Gear witn cruise on. Averaged about 13 mpg.
That's some tune on the RAM. My brother's is stock at 175hp. Even 300hp would be an incredible boost to driveability on the interstates; for skoolies too.
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Old 07-03-2016, 12:38 AM   #5
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I think that's the trade-off for the skoolie - the weight rating is less for cargo and hauling capacity then it is for durability and longevity of the suspension and other parts.
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Old 07-03-2016, 02:41 AM   #6
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That makes sense. But shouldn't the drivetrain be overspeced too for durability and longevity? We work these drivetrains harder than when they were school buses. They just aren't driven as often.
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Old 07-03-2016, 11:41 AM   #7
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Quote:
Originally Posted by BusFiend View Post
Happy 4th, turf! Thanks for this info.


My biggest complaint about skoolies is the totally inappropriate drivetrain for our purpose. Swaps are mega $$$ and beyond most good home mechanics. Skoolies generally require trade-offs and lowered expectations.

I have to disagree to a point.

I certainly do agree that a 5.9 Cummins is not ideal for our application in larger busses. Especially when they stuff an AT-545 behind it. I wouldn't mind one a bit in a smaller rig but would still be looking for an AT-643, MD-3060 or comparable tranny.

Most of the busses that I am looking at myself have a DT466, Cummins 8.3 or a Detroit 671. They are backed by appropriate transmissions such as the Allison 643, 647, 3060 or 740 or a Fuller 6 -10 speed.

I think that those are more than appropriate drive trains for our applications.

"There is no replacement for displacement"

Just my $.02..

BTW: My 2004.5 Ram 3500 w/ 5.9 Cummins is built to about 450hp with the tuner on its top setting. Approximately 375hp on the "tow" setting.
I ran a 5000 mile trip grossing about 22k # and averaged 13.9mpg for the trip.
I would NOT build a bus motor in the same manner. My truck runs 90% of the time with very little load. With a converted bus you are running loaded 100% of the time. A 400hp 5.9 Cummins would likely not have the ideal life span in that application.
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Old 07-03-2016, 01:33 PM   #8
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Originally Posted by BusFiend View Post
That makes sense. But shouldn't the drivetrain be overspeced too for durability and longevity? We work these drivetrains harder than when they were school buses. They just aren't driven as often.
It really just depends on what kind of terrain it was built for. Midwest buses get away with lower HP engines and compensate with deeper gearing but can't even do 55mph. That's why Western and mountain area buses command a higher price for our purposes because they are usually higher HP and geared to do highway speeds because they had to cover a lot of terrain.
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Old 07-03-2016, 09:12 PM   #9
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school busses are often designed for in town trips... durability asied.. they are put together to handle lots of stop n go situations and lots of idling...

wieght-wise im guessing a conversion is a wash or even a little better than a bus full of seats and full of kids..

I do notice that the busses that are used out west do tend to be a bit beefier.. but even those that end up on mountain passes are few and far between... as the bus is still going to be driven with the intention of being stopped shortly so top speed isnt reached or cared about...

Long haul RVing is the opposite purpose.. Powerful busses are out there as some schools bought busses for sports and talent-team use where they knew highway travel would be the norm... or larger city districts where the busses may spend a good bit of time on the freeway..... or out in the country...

plus a lot of the USA is flat or enough so that standard drivetrains handle 95% of the situations normally encountered...

sure there are mountain ranges in the eastern 2/3 of the country but those pale in comparison to the rockies... and how many school districts are in the rockies in comparison to school districts in flat areas of the country.....

simple numbers come up that nice log haul rigs are tough to come by... and like anything commercial expensive to build..
-Christopher
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Old 07-03-2016, 11:21 PM   #10
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Rated Cap: 72
I have paid a number of visits to school bus barns lately looking at buses up for auction.

I see a number of 5.9/545 equipped busses and hear the bus drivers and maintenance people talk about them.

The impression is that the 5.9/545 purchase decisions are (in this area) made by bean counters who are looking more heavily at acquisition cost than at O&M costs.


The drivers love the DT466's and Cummins 8.3's. The maintenance guys love the 8.3's and the old (pre MaxForce) DT466's.

The impression that I got is that if the bean counters had all of the say then all of the buses would have T444's and 6B's. If the drivers and maintenance folks had all of the say then all of the busses would have DT466's and 6C's. Reality.... It is all a big compromise: geography, budget and politics.
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