What engine/transmission to get?

[TrevorH]

With the help of you all and some sleepless nights, I have decided to take a full size school bus and convert it.  My plan being to start with a front engine, truck frontend type skoolie and take off the entire body/floor etc behind the windshield.  Then fab up a body that is 102" wide with plenty of headroom, the full length of the factory bus frame(aprox 35').  It will be driven mainly on the interstate, the interior accomodations will be nice but nothing too crazy, and I will be hauling around 4-5 dirtbikes(aprox 1200 lbs), I will also sometimes be towing my 23' wakeboard boat(dont know the weight).  I currently have a skoolie that fits my size requirements but has a DT360 with an allison 545, thinking about adding a fuller 10spd but dont know if the motor has enough go juice (maybe add propane injection?).  Fuel mileage is at the top of the list.  I'm thinking a manual tranny for the extra mpg's.  What engine and transmission would you recommend for the above setup? Trying to keep it around $6kish for the shell... 

[Dallas]

Hmmm,

I think if I were you, I'd look into buying an older IH, Freightliner, Pete, KW, etc conventional truck with as long a wheel base as possible, then use your bus frame to extend it even more.

That way you get the engine and transmission of your choice and highway gears too.

There are a lot of older tractors out there for 3-4 K that would fit your bill.

[TrevorH]

Good idea but, I am a good welder but dont know if I would trust such a key component to my welding abilities.  Would be difficult to be precise, level, etc.  Wouldnt the large motor in a semi be way overkill and thus cost me fuel mileage?

[TomC]

First off toss the Allison AT545.  Since it does not have a torque converter lockup, it will be slipping all the time at freeway speeds creating lots of heat and getting less than desirable mileage. 
The DT360 puts out about 450lb/ft of torque-about half of what you should have.  My suggestion is to find a DT466/530/570 that is around 300hp and 800lb/ft torque and use either a MT643 Allison 4 spd or the excellent Allison 6spd World transmission-that would be the MD3060, MD3066, MD3560, 3000HS, 3000RDS, etc.  Look for a crunched schoolie or straight truck that has the DT466 and auto trans, then remove everything including the wiring harness and shifter-buying those items separately can be expensive.
If you're going to remove the complete rear end of the bus, why not start with a medium duty truck like a Freightliner, International, Ford or GMC-they usually have a stronger frame than the schoolie.
I know with Freightliner (since I sell them) that the 33,000gvw trucks have virtually the same axles and frame as our big over the road trucks.  Currently the top horsepower in our M2106 is the Cumminis ISC at 330hp and 1000lb/ft of torque-more than enough power-it is rated for truck use up to 75,000lbs.
Personally-from my own bus and the large amount of money I've spent to get the power train right, buy a used truck (there are lots of them) with the correct engine you want.  If you want to change to an Allison HT740-there are shops that can do it for about $10,000.  Good Luck, TomC

[Dallas]

Good idea but, I am a good welder but dont know if I would trust such a key component to my welding abilities.  Would be difficult to be precise, level, etc.  Wouldnt the large motor in a semi be way overkill and thus cost me fuel mileage?

For the welding, you could always take it to the local tech school and let them do it... they would love real world application to teach the students.

The large motor in the truck doesn't have to stay large. In my last truck, a IH 9670 cabover with a Cummins Big Cam IV pushing 400 HP and a Fuller RTOO14613, my differentials were geared at 3.73:1. I averaged 5.67 mpg over the period of a year. Most of my loads were OD and my average weight was over 105,000 pounds. I think that pulling a 35' box weighing less than 30,000 lbs would increase your mileage dramatically.

You may also want to consider that the truck frame is built to haul heavy loads on and off road. The suspension can be set (with air ride) to be comfortable, but still firm enough to handle abuse, and if you have air ride, you can set it up to manually level when parked at the campground or bike trail.

[TrevorH]

What kind of mileage would you think I would be able to achieve with that setup?  I completely understand that we are just shooting from the hip.  But it will help me weigh out the pros and cons.  Also any ideas on what I should be looking for that would have that engine/tranny setup?

[tekebird]

schoolie is not the way to go iIMHO......

I'd go with a medium duty Expiditer truck, they are a dime a dozzen because most of the freight shippers require a 4 year old or newer truck for thier owner operators.

as for the 102 vs 96......it all depends on your layout.  I have been in 102's that are alot more cramped than other 96's.

the A 3 I bought my folks though was a 102 the way it was layed out....alot more room than the other three 96" wide buses in the family

[Dallas]

What kind of mileage would you think I would be able to achieve with that setup?  I completely understand that we are just shooting from the hip.  But it will help me weigh out the pros and cons.  Also any ideas on what I should be looking for that would have that engine/tranny setup?

I know when we were bobtail, our fuel mileage could be counted on to be in the mid to sometimes upper teens. Normally though it was around 14-16. As a bobtail we weighed in at less than 16K.

With an empty flatbed trailer it was a little less than that and probably averaged around 11-13 mpg. 33-35K

If we were accidentally  pulling a dry box van trailer we could figure around 8-9 mpg empty. 34-36K

Look for a truck, whether it's a Class 7 or Class 8 that has gears low enough to walk you into and out of places that buses have a hard time with, and also has upper gearing that will send you down the road with your tach in the sweet spot.
You don't need a lot of horse power, but a 3406B or C Cat engine set at 350 to 400 or a Cummins set up the same way or a 12.7L Detroit 60 series would give you all the power and torque you would ever need.

One nice thing about a full twin screw tandem axle class 8 tractor is that if you start slipping you can kick in the power divider and have 4 more tires pulling you. Much nicer than having an air tag that can cause no end of traction problems under off road conditions.

You may also want to remember that if you choose a Class 8 conventional tractor, there is going to be 10' of hood and bumper out in front which is unusable. My preference would be a cab over to keep the length as reasonable and as usable as possible.

[HB of CJ]

Dallas is really onto something here.  Lots of good, older, used tractors can be had for very little $money$.   They may be a little bit tooss tired for heavy hauling, but would work just fine for your application.  Find a nice bobtail and lengthen the frame to your desired length.  You probably will only need two (2) axles with your projected all up weight.  I bet if you kept your foot out of it, you could get eight, maybe ten miles per gallon at a reasonable road speed. 

[buswarrior]

Yes, absolutely choose a truck chassis instead of a skoolie.

You will kill yourself trying to remove the school bus body, they are built like tanks, to protect the little kiddies. And hanging toys in that long rear overhang has a real potential to lighten the steering, letting the front hunt around at highway speed.

If you go all out and get a tandem axle, if you are going off road, you really want the full locking differentials, 4 way locks, not just an inter axle power divider. You want all 8 turning, locked together, to get out of whatever excellent adventure you have taken on.

There are lots of "long cars" out there, stateside, highway tractor tandems with 270" wheelbase and longer...check the auto-trader heavy truck equipment edition in your area.

Trucks and buses are awfully easy to get stuck, compared to a light duty personal transport, and cost exponentially more to unstick.

happy coaching!
buswarrior

[TrevorH]

So for my application, what would the pro's and con's of a dual axle rearend?  What is the longest length that I could extend the rear axle to do as far as wheelbase is concerned?

[tekebird]

ther eis a very nice expidited chassis sleeper on ebay right now.

I think a three axle truck is way overkill for your application not to mention the increase tire and maint costs.

[TomC]

I'm in the designing stage of my next motorhome-using most likely an Freightliner Argosy cabover.  I want to keep it to 40ft (too many campsites that don't allow over 40ft) so with a tandem rear end and having 12ft of over hang behind the rear most axle, and with a 40" front axle set back that works out to be a 270" wheelbase (measured from the center of the front axle to the center of the two tandems in the rear).  So the measurements work like this-40ft=480" minus 40" front axle set back, minus 144" (12ft) rear overhang to the rear most axle, minus one half the distance of the tandem spread to get the middle of the tandem- 26" = 270" wheelbase.  This will keep the chassis well balanced, but not to long for good turning radius (270" is how long our Freightliner Classic XL wheelbase is).  Good Luck, TomC

[rv_safetyman]

Chiming in here a bit late. 

I built a motorhome (actually a toterhome) on an IHC Class 7 chassis.  It had a DT466 (very durable engine) with a 5 speed plus two speed (with the gears, this was close to being the same as a nine speed truck transmission).  The engine was rated at 210.  It was a mechanical engine.  I had it turned up a bit, but it was no where near the power really needed.  My truck had a GVW of 34K and weighed about 24K.  I had to really row the gears on the hills in MO and it was a real challenge in the mountains.  I did haul a small car trailer once and it was not a lot of fun.

I drove a similar truck with an electronic DT466 (about 24K, 7 speed) for many miles when I was teaching a class around the country and it was no better.

You have been given good advice!  DO NOT SETTLE FOR LESS THAN A CLASS 8 TRUCK.  Go to any truck stop and there will be several paper type publications with hundreds of used trucks for reasonable prices.

You will generally get a much stronger engine, Jake brakes and BIG air brakes.

Jim

[tekebird]

http://cgi.ebay.com/ebaymotors/NEW-07-DAMON-OUTLAW-3611-TOYHAULER-SINGLE-SLIDE-LOOK_W0QQitemZ310013551826QQcmdZViewItem?hash=item310013551826