Seeking Bus advice - Thomas CAT engine

cesar.quattro

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Apr 3, 2018
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Hey everyone, I've been looking for a bus to purchase for nearly 2 months and I recently found a 2003 Thomas CAT rear engine, Allison transmission with 118k miles. Does anyone have experience with cat engines?

I did a quick VIN search provided by the bus owner and I got this info: image attached
Nowhere in the report does it say it has a cat engine it just says it's a 6 cycle diesel?? It also doesn't mention anything about the transmission.

I'll mainly be stationary, I'll probably tavel 2-3 times a year.
 

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It's a cat engine, but I cant tell if it is a 3126 or c7. Both were put in buses as I hear, but possibly the 3126 was more popular in school buses? Hopefully one of the experts will show up and confirm shortly.
 
The owner did say it has a CAT engine but I can't find where it says it on the VIN report.

You think a 6 cylinder is enough for the weight it will be pulling?
 
Absolutely. That engine, whether a c7 or 3126, is likely between 250 and 300 horsepower. Plenty to carry a bus loaded with people most anywhere. It would not take much more than a trip to the cat certified repair shop to have it re-rated to a higher horsepower should you feel the need to do so.
The trans is likely as stated, an Allison. An excellent transmission. One of the most robust and easy to use transmissions ever. Probably a 5 speed.
I will mention, even though you may already know this, there is no "Park" position with these allisons. You put it in neutral and set the park brake. Set the park brake every time you leave the seat.
 
Awesome but I'm wondering if it's capable of pulling the weight of a converted bus.

I'm kinda new to this website, you think I should post this somewhere else in another thread so more people see it?
 
Seldom would you need more power even with a conversion. You'll over load the axles and tires before you'll run out of power. That said, it can be a preference to have gobs of power to pull 65mph over the steepest of hills. But all that comes at a fuel cost.

Think of each kid weighing 100 pounds on an average. Likely it would be more if you have a lot of high schoolers on the bus. But that's well over 4 ton of peopleon an 84 passenger. Not sure what they consider your bus to be, but even 4 ton is a lot of lumber and appliances.

If you can find the curb weight on the bus, that will tell you what you are starting with and then the gross weight rating, which should be listed on the bus will give you the max the bus can weigh loaded. Probably somewhere around 32 to 34k.

This is the right place to ask. It takes time for people to end their week and get around to setting down at the computer and opening skoolie. You'll get some good answers coming up. Meanwhile you can also use the search feature and find a lot about the bus you are looking at that others have worked on or maybe now driving.
 
Great! Hey thanks a lot for all the helpful info, it feels like I've been in the search for the "perfect" bus though it's not as easy at it first seemed.
 
I feel your pain. I just put up a thread about finding my bus after months of looking, then getting an offer I could'nt refuse on it before I even brought a wrench to the first seat bolt.

If the bus you are looking at actually is a no rust chassis and body, that is a rare keeper. Cat and cummins are the usual engines and both are excellent engines for buses of all shapes and sizes. Allison is the industry standard for transmissions. They basically set the bar for all others to attempt to meet.

The pictures look great as far as I can see. I tend to prefer conventional buses as the overhang over the front axle is something I do not like. But it is a trade off that I choose. The rear engine is so much quieter for the driver.
 
While Allison does make several bus transmissions, the AT545 is the least desirable for most conversions that plan on spending much time on the open road. It will likely only be able to go 55mph. It is not intended for long stretches of high speeds 60mph+, or for pulling the weight of your Skoolie over large mountain passes. I waited and found a bus with a Cat and a 3060.
Seldom will your conversion way anywhere near what a full load of passengers weigh. I'd be curious to see what some of these conversions weigh with a full array of solar panels and an upper full deck.
 
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2003?

That will likely be a CAT 3126, predecessor to the C7

This was one of the few final years you would see the 3126 and this also means most of the kinks and updates have already been incorporated into this engine

Should be 300 HP and 700 or so ft lbs of torque

Plenty to push the bus
 
The owner did say it has a CAT engine but I can't find where it says it on the VIN report.

You think a 6 cylinder is enough for the weight it will be pulling?
For sure...6cyl diesel is a lot...it's the tranny and diff that is gonna determine speed
 
Try the Gates VIN decoder;

https://www.gates.com/search-by-vin

It'll at least say the engine mfr and displacement, and that's usually enough to narrow down the model.
I just tried this and it says invalid VIN any ideas why??
My insurance company also told me it didnt come back correctly, however i read the VIN on the Title.. and even submitted a picture of the titile

DOESNT MAKE SENSE TO ME...
 
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Do you have pics of the data plates inside the bus? That will tell you your gross weight and axle ratio. Often will also include tranny model, or at least the tranny serial number. I would be shy of buying that bus with an AT545 transmission, but with any other model, I'd jump on it.
 
Do you have pics of the data plates inside the bus? That will tell you your gross weight and axle ratio. Often will also include tranny model, or at least the tranny serial number. I would be shy of buying that bus with an AT545 transmission, but with any other model, I'd jump on it.

The push button shifter would indicate a 2000/3000 series transmission. Given the year I would bet that it is an MD3060.
 
2003?

That will likely be a CAT 3126, predecessor to the C7

This was one of the few final years you would see the 3126 and this also means most of the kinks and updates have already been incorporated into this engine

Should be 300 HP and 700 or so ft lbs of torque

Plenty to push the bus

Don't let a CAT 3126 put you off buying, just check the condition.

Do let the C7 encourage you to walk away, and if it has already grown-up into the ACERT ... run away.
 

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