weight and towing

turf · 07-02-2016, 12:12 PM

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

BusFiend · 07-02-2016, 06:21 PM

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

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

somewhereinusa · 07-02-2016, 06:56 PM

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.

BusFiend · 07-02-2016, 07:57 PM

Quote:

Originally Posted by somewhereinusa

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.

Mark_In_MA · 07-02-2016, 11:38 PM

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.

BusFiend · 07-03-2016, 01:41 AM

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.

PNW_Steve · 07-03-2016, 10:41 AM

Quote:

Originally Posted by BusFiend

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.

jake_blue · 07-03-2016, 12:33 PM

Quote:

Originally Posted by BusFiend

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.

cadillackid · 07-03-2016, 08:12 PM

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

PNW_Steve · 07-03-2016, 10:21 PM

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.

crawler · 07-04-2016, 10:11 AM

Hello Turf
You did look a little relieved to be over the pass when I saw you the other day.
I think power trains and gearing are somewhat of a trade-off my bus pulls the pass fine but will only run 60 on the flat. A re-gear is out of the question for me because I will be around the continental divide a lot and it is not an easy task with a RE bus. So I just have to live with slower highway travel.
Soon I will be retired and travel will not be rushed so the only problem will be the people behind me that are still trying to get somewhere in a hurry.

Tango · 07-04-2016, 10:18 AM

Not sure what size tires you are running, but going larger in diameter will get you a few more MPH. You can determine just how many by using the calculator below...(the one at the bottom especially)...

Engine RPM Calculator

crawler · 07-04-2016, 10:42 AM

Tango
You hit the nail on the head, the rear stock size tires were replaced with low profile tires by the school system (for whatever reason?).
I have a deal in the works with a truck tire dealer he has use for the low profile tires they run them on some flatbed trailers to reduce load height.
I am anxious to get this completed he will match the two front tires and spare (Michelins) with 1 more to put on rear, and new tires on front. Then I will just have to go for a run to find out how the speed will change.

turf · 07-04-2016, 10:43 AM

pulling up the pass was tough. if anything, i need more power, and a transmission that wont slip under more power. i remember that peak torque is at lower rpm's, so i try an ease off the pedal and go slow. the incline was steep and long and a few times the trans gives away and slips.

not sure if it was my head or for real, but the next 100 miles of so it just felt like i was a pulling an anchor. after a fuel stop, the truck felt normal again.

i dont think the motor/trans would push bigger tires. i have 11x22.5's now. i am considering a flush and fill of the transmission.

crawler · 07-04-2016, 11:04 AM

the pass is steep frequently we see a motor home broke down and being towed back down, or a pickup with large camper. most of the time the radiator is steaming or the transmission has lost a large amount of fluid on the road. Sounds like a good idea to service the transmission.

cadillackid · 07-04-2016, 11:13 AM

Quote:

Originally Posted by crawler

the pass is steep frequently we see a motor home broke down and being towed back down, or a pickup with large camper. most of the time the radiator is steaming or the transmission has lost a large amount of fluid on the road. Sounds like a good idea to service the transmission.

as much as I like the good old AT545.. I surely would NOT want one on a steep pass..

transmission fluid can and DOES boil...

lugging a transmission WILL get it hot... by lugging it i mean running it against the stall speed RPM of the UNLOCKED converter and the differential between converter shell speed and transmission inpiut shaft is high... you will make TONS of heat..

a Lock-up transmission like an MT643 or the allison 1000,2000,3000 is a MUST in the serious passes...

as is a transmission cooler... just servicing the transmission wont prevent it from over-heating.. and all it takes is ONCE with the fluid 250 degrees and that transmission will cook...

servicing it will not hurt it.. but also make sure its ready to run a mountain climb like that... an external fan-forced cooler and a trans temp gauge at the very least..

-Christopher

Tango · 07-04-2016, 11:32 AM

I am totally on board with Chris. A temp gauge & plenty of cooler area are critical to tranny survival. It is also worth checking factory specs to see if any of the newer synthetic fluids are compatible as they handle heat much better than the older non-syn types.

Below is yet another temp/mileage chart worth reviewing if you have any doubts about tranny temps and fluid serviceability. It is consistent with Allison's own numbers for "conventional fluid". The syns are a bit better.

Hayden - Transmission and Engine Oil Coolers

crawler · 07-04-2016, 11:33 PM

yes I like the mt643 with the large cooling system I have not experienced any high engine or transmission temperature's while pulling any of the passes. The auto-chains are also nice if you have to go when chain law is on.

cadillackid · 07-05-2016, 06:26 AM

Quote:

Originally Posted by Tango

I am totally on board with Chris. A temp gauge & plenty of cooler area are critical to tranny survival. It is also worth checking factory specs to see if any of the newer synthetic fluids are compatible as they handle heat much better than the older non-syn types.

Below is yet another temp/mileage chart worth reviewing if you have any doubts about tranny temps and fluid serviceability. It is consistent with Allison's own numbers for "conventional fluid". The syns are a bit better.

Hayden - Transmission and Engine Oil Coolers

can I run syn in my AT545?

I swear i read somewhere that the front pump in the AT545 cant build pressure properly with the syn fluids lower overall viscosity.. of course now i cant find what I was reading..

-Christopher

Scooternj · 07-05-2016, 06:52 AM

Quote:

Originally Posted by cadillackid

can I run syn in my AT545?

Over on School Bus Fleet, there's a discussion about synth in an AT-545. You can, as long as its on Allison's approved list, and used with the right filters, including internal.

You may also like: