Dream Machine

[oldog12]

So... What combination of engine, transmission, rear end and body would make every one's knees tremble with anticipation???

[eggman]

I am really happy with my DT466 and AT545......only thing that could make it better is if it had the AT643 in it. 7 hours is the longest that I have driven it, did 11 mpg pulling a 7K trailer.

Just my $.02

[frank-id]

These buses were made for a very long tima at about 80 years. The body shape changed little and remains a good looking bus. The Crowns were made in several lengths including 35 and 40 feet. The engines of modern Crown buses have been Cummins and Detroit diesel. The engine have been located midbody under floor and later buses were pushers. Crown buses were made as postal units, tour buses, city buses and school buses. Mostly Crown buses are found mostly on the left coast in Ca, Wa, Or, Az, and occasionally in other nearby states. The last buses were made about 1991. The beautiful rounded bodies are a design of old world class. Mechanical parts are easily found. Ca is presently destroying many Crown buses to satisfy the new clean air laws. Used Crown buses seem to slowly increasing in price and value as the bus is discovered. Average price for a Crown is between $3500 and $5000. There is high degree os parts interchange from many years models. Every time I get into my Crown, my face becomes a smile. I've tried the Greyhounds, transits and other tour buses. Nothing beats a Crown bus. Frank

[Steve]

I agree with Frank, if they had Crowns around here I would own one. They have such a classic look to them that other buses have not had in 30 years.

[the_experience03]

It's a twinkie with headlights and wheels. I sure wouldn't mind one with a 671 and 10 speed road ranger.

As for my bus...my body and chassis could have been speced with the 7.8 Brazilian, 13 speed Road Ranger, and air ride. While the 7.8 doesn't have the following that the DT466 does, it does have plenty of power and is reliably simple. The 13 speed would be great for mileage, pulling hills, etc. Heck...even the RT6610 10 speed would have been ok. And honestly...how many of us WOULDN'T want air ride?

[oldog12]

And honestly...how many of us WOULDN'T want air ride?

Ooooo Air Ride.....

Can't remember where I read about some carrier beam problems... Something to do with drive shaft geometry I think...CRS (Can't Remember S***t) strikes again!!

But I digress, what about the rear end? I'm a little confused as to what I should look for if I'm planning on hooking up a toad given that the engine will probably be a Cummins 5.9 with a MT643...

Whachya'll think ????

BTW Crowns DO have that classic look about them...

[the_experience03]

Toad or not, I don't think you need to be gearing for power unless you plan to sped A LOT of time in the hills. My bus has 4.56 gears and that's all the lower (numerically higher) I'd like to be geared. A two speed rear end would be nice, even with an automatic.

[oldog12]

So a 4.11 is not a good idea???

[the_experience03]

4.11 would be a GOOD idea. Low gears are numerically high. 4.10 is a "higher" ratio than 4.56. It is counterintuitive. At freeway speeds our buses make plenty of power and do not need that extra gear reduction. The higher gears will give you a better top end, a happier engine, and better mileage. Many buses were geared in a compromise range, mine included. 4.56 wasn't ideal for log trips, but was better for the typical start and stop traffic a bus on a rural route might see. A bus in a city like Duluth here might have 6.17 gears. The distance between stops is short and this town is on something like a 6% average grade. You'll notice that often the same buses are used by high school sports teams for "away" games. This is because they were speced with the best gearing for the job, underbody storage, etc. Those are the ones we want as converters.

[Elliot Naess]

Those are the ones we want....

Known as Activity buses or Field Trip buses.

I'm still hoping to find more information on two speed rear ends. A servicable
used "pumpkin" might cost a heck of a lot less than a Gear Vendors unit! If anybody
has a clue, my rear axle is a Spicer J-190-S according to the build sheet.

About finding an Allison MT643 behind a Cummins 5.9, or any engine below 235 HP,
look for a GVWR (Gross Vehicle Weight Rating) above 30.000 Lbs. The AT545 is
limited to 30.000 Lbs and 235 HP.

(Edited to correct HP rating.)

[the_experience03]

Isn't the Gear Vendors unit only rated to something like 10,000 lbs GVWR? Even if it was rated for more...marrying it to any transmission other than the typical TH350, TH400, SM465, Muncie car trannies, etc would be a pain.

[Elliot Naess]

They put Gear Vendors boxes in Class A motor homes.
For commercial service they say max 25.000 lbs, but I don't see a limit listed
for recreational use.

And they can be installed "free standing" with a drive shaft on each end.

But those things cost thousands.

[Elliot Naess]

Ooooops...

Correction: Only 235 HP for AT545. It's the MT643 that can take 250 HP.

To recap:
AT545 -- 235 HP and 30.000 Lbs -- no lockup.
MT643 -- 250 HP and 73.280 Lbs -- locks in 3rd and 4th.

[oldog12]

Man... I'm still playing with crayons compared to you guys !!

[Elliot Naess]

How so, Oldog? Ask questions -- somebody here will get you up to at least watercolors
in a hurry!

Everything takes learning. 18 months ago I didn't have a clue about buses either.
So I started reading on this and other web sites. Then I bought a $250,- bus and learned
a lot from toying with that and driving it on two "expeditions" (and then I scrapped it).
And I pick the shop foreman's brain at work. Everything takes learning.

[the_experience03]

Good to know about the GV unit, Elliot. I had never heard of one being mounted in a divorced setup, but sure isn't tought to go from married to divorced mount. The other way is a bit trickier...

What is the maximum input torque on the AT545? The first Series 1000 Allisons in the GM pickups were rated at 520 ft lbs I believe and I would imagine our ratings are very similar. Interestingly enough, the Allisons in the Duramax trucks have lagged behind the engine output in terms of input torque max.

The reason I ask is because I plan to up my fuel rate come spring. I'm not interested in more top speed right away (though I will likely turn the governor up later on). I just want a little more power on reserve in drive on the highway. My engine most certainly runs out of fuel on the top end. From the factory my particular turbocharge and intercooled 6.6 Brazilian was rated at 185 hp and 474 ft lbs. It isn't a tremendous amount of power, but it is the H.O. version of the 6.6. It only makes 5 horsepower less than the bottom end 7.8 Brazilian. I'd like to bump the horsepower up into the 200-210 range (seat of the pants dyno, mind you), but I'm concerned what this will do to my torque. A 25 horsepower increase may well give a 50 ft lbs increase putting me dangerously close to AT545 shredding terrain.

[Elliot Naess]

AT545 max input torque is 445 lb ft.
MT643 -- 640 lb ft.

No, I don't walk around remembering this stuff!
It's all right here: http://www.industrialautomatic.com/html/onhiway.htm

[the_experience03]

Well...that makes me a little nervous given the fact that my 6.6 is rated at 474 ft lbs at the crank stock. I suppose there is some room in there given that the 474 is lower in the powerband and not really something it would be subjected to constantly. Do I need to be concerned about turning my pump up? What is the 6BT Cummins putting out for peak torque?

[Elliot Naess]

What is the 6BT Cummins putting out for peak torque?

I suppose I could look that up, but I don't need to -- I have the big tranny.
BWWWAH-HAH-HAH-HAH-HAH-HAH!

Oooo, this is fun!

[boojiewoojie]

Well, I would love a tandam axle Crown bus with a 10-speed. That would be classic.
How expensive are the parts to put in a 4.10 rear end? Is it something a shade-tree mechanic can do?
Rick