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Old 10-14-2004, 01:38 PM   #1
Mini-Skoolie
 
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More Questions, more organized

Alrighy, the other day I had some pretty unorganized questions. Let me try again.

Good or bad, if bad why?

Engine

1. Cummins 5.9:

2. DT360:

3. DT466:

4. Ford 6.6:

5. DT408:


Trannys

AT545:

MT643:


Any comments on good drivetrain combos? Gas is not acceptable.
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Old 10-14-2004, 07:16 PM   #2
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#1 Cummins 5.9 is an ok engine but does not hold up very well in school bus service. Great in a pickup but not very great in a bus. It is the standard cost effective engine in a lot of buses.

#2 DT360/366 Great engine but it lacks some power. It is expensive to rebuilt as most Navistar engines.

#3 DT466 another great engine and you can get it up to 230 HP in a school bus. The DT466 is still a Navistar engine and expensive to rebuild.

#4 Ford 6.6 If I remember correctly this is the Brazillian engine and it is supposed to be a great engine as reliability goes. I have heard from several sources that it is a dog though. In fact I think Jason on this group has this engine in his bus.

#5 DT408 I have not seen this engine is a school bus.

#7 T444E/7.3 I always hear bad stuff about this engine, I would stay away from it. You will find a lot of school buses under 100k miles with a new or rebuilt 7.3 in them.

#8 Cat 3208 The cat 3208 is a sleeveless engine so rebuilding them is not easy. The 3208 is a good engine though and it very common in transit style school buses. This engine is a V8 and is not the best on fuel but it is a good engine.

Transmissions

#1 AT545 this is the Cummins 5.9 of trannys. The AT545 is cheap to buy and just "ok". The AT545 is not a real beefy tranny and does not hold up very well is harsh service.

#2 MT643 This is a much better tranny with overdrive. It will hold up better with heavier loads and will last longer.

For all the technical tranny info check out this site
http://www.industrialautomatic.com/html/onhiway.htm

HTH
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Old 10-14-2004, 07:43 PM   #3
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that was an excellent reply to the original post.

I do have the brazialian made 6.6 liter ford. All indications is that this motor is indestructable, however, it is wimpy and parts are really expensive. My skoolie has over 276,000 on the original engine without a rebuild.

The 5.9 liter cummings: I would not buy a bus with this motor in it,especially the new compuer controlled 5.9. I'd be more than happy to have that engine in a dodge 4x4 pickup however.

The DT360 from what i read is more reliable than the dt466. Both are excellent engines.

The 360 although it is smaller by displacement than the ford 6.6 will run circles around the braziallian motor when it comes to performance. Fuel economy will be much less in a 360 than a ford 6.6. This info comes from the friendly guys at my local bus garage. They currently run both engines in 72 passenger busses. The dt 360 should get close to 7mpg, while the 6.6 gets 8.5. both use the 545 allison.

I would also like to disagree about the cost of rebuilding the dt360. According to my local bus mechanic, an entire rebuild kit can be purchased for under $1,000 bucks. This motor has sleeves and the entire engine can be rebuilt while it's still in the vehicle.

I wouldn't compare the 545 allison to the 5.9 cummings. The 5.9 is a bad skoolie engine! The 545 is very common around here in buses. It's pretty much the only auto trans i've seen in used buses here in michigan. It is pretty reliable, the biggest downside is that It does not have a lock up converter, giving approximately a 10% decrease in power and fuel economy over a manual trans. My bus (1991 Ford 6.6 allison 545) did get a new trans at approx. 150,000 miles. I don't know if this is premature failure for one of these transmissions or if 150k is par for the coarse.

There is a bus on the lot right now with a bad at545 allison, it has about 250,000 miles on the bus. I'll try to investigate and see if that is the original trans.

hope this helps.

In my next bus, ideally i would like a dt466, but i'll settle for a dt 366
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Old 10-14-2004, 07:46 PM   #4
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one more skoolie diesel worthy of mention is the 9.0 liter internation. According to Greg (who has spent years buying and selling hundreds of used busses) will last pretty much forever. It is huge motor when it comes to displacement, but it makes 180 hp or less making it every bit as whimpy at the ford 6.6 liter.

if you want a motor you won't have to work on, the 9.0 liter is the one for you.
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Old 10-14-2004, 11:54 PM   #5
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Good point about the 9.0L it is an awsome engine. Not much power but it keeps going and going. It is also excellent on fuel. The AT545 is fine for regular school bus use but I would not want to be hauling and towing cars with it. The MT643 does have a lockup converter and is a much beefier tranny. If I found the right bus at the right price with an AT545 I would probably still get it. I would not however be running it at a full load all the time.
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Old 10-15-2004, 12:17 AM   #6
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I can't speak from much experience, but my bus has the Ford 7.8L engine. It's basically the same block as the 6.6L with just a longer stroke. At least that's what I can find out about it anyway! The 7.8 is also a Brazillian engine and seems to have plenty of power with the 5-speed manual transmission I have. I can hold 60 no problem, and 65 isn't too much of a stretch either.

About the only down-side I have heard about the Brazillian motors is that parts are pretty expensive and hard to come by.

Good luck!
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Old 10-15-2004, 10:08 AM   #7
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Hi,

I have a Blue Bird/International (65pax) with the DT466 and MT643 Allison automatic. I drove this bus home from Denver to Seattle, some around our area and just finsihed a round trip from north of Seattle to Redding, CA and back (nice hills!) pulling a 16' boat. I'm very happy with the powertrain and the power available; I'd like a little higher gearing for a bit more speed on the highway and to get the rpm down a bit (right now it runs 57mph at 2600rpm) but it pulls the hills well. So far, in the 4,000 or so miles I've driven the bus, I've maintained just a tad over 9 mpg; worst was about 8.75 pulling the Continental Divide and Lookpout Pass on I-90 coming home from Denver. We got just over 9 mpg overall on the Redding trip with the boat in tow. Right now the engine is set at 180 hp, it can be dialed up to 210 hp at the shop if I want to go that way.

A friend of mine who owns a coach company (and has everything from vans to MCI road coaches) told me to lok for the DT466/MT643 combination...so far I've been very happy with that advice.

I was told to pass on any DT466/AT545 combo I came across; I was told the torque from the DT466 can really beat up an AT545. In an attempt to save money some school districts did specify that combo and I have seen them advertised.

As evidenced by the large number of older and still running gas and diesel skoolies on the road the DT466/MT643 certainly isn't the "only way" to go; I'm sure there are lots of folks happy with other combinations and I just wanted to add my experience with my set up here.

Happy Bussin'
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Old 10-15-2004, 01:56 PM   #8
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Awesome response, thanks.

I am rather confused about the 5.9 cummins. I am getting lots of advice, both on totally opposite ends. I will probably end up getting the 5.9 and at545, but I am searching hard for the 466/MT643 combo. If I get the AT545 I am assuming a swap to the MT643 will not be much of an issue, a near bolt in. I do all my own welding, advanced mechanical work , and fabrication so from what I have been told maintence shouldn't be hard just A LOT BIGGER tools required???(question)



Here is another question I have. Most of these diesel motors have huge displacments with extremely small outputs (tell me torque not horsepower). I have known quite a few people to release power from their diesel by installing a free flowing exhaust, intercooler, higher govener springs. Has anybody tried this? now understand I am talking about releasing power that is already there, not messing with injection pumps or doing things that might cause harm.....and all of this assumes an EGT Gauge has been installed. This is another reason I am looking at the cummins, because high amounts of RELIABLE power are available out of it....assuming it holds up.
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Old 10-15-2004, 09:16 PM   #9
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The Cummins 5.9 is great in a dodge pickup because load does not weigh as much and in most cases rarly ever moves a really heavy load. In a school bus it takes a beating always starting and stopping and idleing. It also is powering a heavy vehicle that can hold a load of heavy kids. The AT545 will probably hold up ok in regular bus service but I would not want one if I was going to have a heavy conversion like hauling cars. If you can find a bus with a Cummins 8.3 you will be able to get more power out of it easy. Another problem with the AT545 is it is rated for 230 HP 445 lb ft. If you can find one with the MT643 and an 8.3 you will be set. The MT643 is rated for 250HP and 640 lb ft. Of course if you are going to put in a manual you could get higher HP and not worry about burning up your tranny. If you could find a Gillig or Crown bus with a mid ship mounted engine you would still be able to carry a car in the bus and you can find them with IIRC a 12 speed tranny. Those also have a 6v71 or a Cummins 555. Those are ancient engines but you might be able to get some HP out of the Detroit. To take a look at some Gilligs and Crowns check out http://groups.msn.com/TheGilligCoachClub/.
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Old 10-15-2004, 10:55 PM   #10
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One of the reasons medium and heavy duty diesel engines last so long is the high iron to hp ratio. You're correct, there seems to be very little horsepower compared to the large displacement of any big diesel engine. You can increase the horsepower of an engine, the downside is that you will reduce the lifespan of the engine. higher hp=decreased engine life.

2000, 2001 Lapeer Community Schools purchased several buses with the cummings 5.9 rated well above 200 hp. That's a lot of horsepower from what is probably the smallest commonly availabe diesel for skoolies. Nearly every one of these buses has been towed back to the cummings certified repair facility for new a new injector pump at least once. They are really happy with the performance of these motors, but the engines just keep blowing themselves apart. Now they order all their buses with cat motors, i forget the model.

I would not buy a bus with a 5.9 liter, or the 555 (triple nickle) cummings.

If you really want high performance (i use that term loosly), buy a big gasser, like a fuel injected 454.
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