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Old 07-12-2018, 12:32 PM   #1
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Mountain driving - which engine/transmission

Howdy,



I am searching for a bus to fit my needs and am curious if any of the knowledgeable folks here can point me in the right direction.

I'm looking to full time in the bus, and will be in the mountains for a majority of the time, as well as put in a lot of miles on the interstate traveling between destinations. I'm leaning more towards a shorty, as I feel many mountain roads will be too twisty for me to comfortably or safely drive a full size bus.


Basically wondering which types of engines or transmissions I should be looking towards, and any that I should steer away from. I appreciate any feedback or tips! Thanks
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Old 07-12-2018, 01:14 PM   #2
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Are you thinking of "mountain roads" as in unimproved logging roads, forest service roads, or paved two-lane county and state roads?
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Old 07-12-2018, 01:25 PM   #3
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Short answer: you do NOT want an Allison AT545 transmission - it freewheels down hills and overheats going up.
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Old 07-12-2018, 03:14 PM   #4
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Quote:
Originally Posted by family wagon View Post
Are you thinking of "mountain roads" as in unimproved logging roads, forest service roads, or paved two-lane county and state roads?

When the term mountain road comes to mind, the paved two lane roads were what I was referencing. I'll probably have a bike as well, and love hiking, but something that could tackle the steeper grades is my main concern. I'd love to hear any suggestions for the unimproved roads as well, as I do foresee many of those in my future.


Dapplecreek - Thank you for the information! Does the term freewheel reference the fact that the transmission will not hold you back and help to moderate speed?
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Old 07-12-2018, 04:46 PM   #5
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Exactly! The AT545 does NOT have a lockup torque converter, so there is no mechanical connection to the engine, only a fluid coupling. Very minimal engine braking, with lots of slip and wasted energy going up hills.
An MT643 is a good solid 4-speed, the 1000 and 2000 series are solid overdrive 5&6-speed trannys and the MD3060 is a very solid 6-speed transmission. *However* if you want to use the full capabilities of them, make sure 6th gear is unlocked as some of them have it locked out.

My dream setup would be a 250+HP DT466 or a Cummins 8.3 mated to an MD3060 transmission with around a 4.11-4.38 geared rear end!

John
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Old 07-12-2018, 05:26 PM   #6
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Originally Posted by johnbloem1974 View Post
Exactly! The AT545 does NOT have a lockup torque converter, so there is no mechanical connection to the engine, only a fluid coupling. Very minimal engine braking, with lots of slip and wasted energy going up hills.
An MT643 is a good solid 4-speed, the 1000 and 2000 series are solid overdrive 5&6-speed trannys and the MD3060 is a very solid 6-speed transmission. *However* if you want to use the full capabilities of them, make sure 6th gear is unlocked as some of them have it locked out.

My dream setup would be a 250+HP DT466 or a Cummins 8.3 mated to an MD3060 transmission with around a 4.11-4.38 geared rear end!

John

Thanks for the info John! It is going to help greatly in my research and search for a bus! Can't wait to get in the mountains!
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Old 07-12-2018, 07:18 PM   #7
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Quote:
Originally Posted by johnbloem1974 View Post
Exactly! The AT545 does NOT have a lockup torque converter, so there is no mechanical connection to the engine, only a fluid coupling. Very minimal engine braking, with lots of slip and wasted energy going up hills.
An MT643 is a good solid 4-speed, the 1000 and 2000 series are solid overdrive 5&6-speed trannys and the MD3060 is a very solid 6-speed transmission. *However* if you want to use the full capabilities of them, make sure 6th gear is unlocked as some of them have it locked out.

My dream setup would be a 250+HP DT466 or a Cummins 8.3 mated to an MD3060 transmission with around a 4.11-4.38 geared rear end!

John
Hummmm, I have the 8.3 with a MT647 & 4.10 rearend, What do I need to know about that setup?
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Old 07-12-2018, 08:24 PM   #8
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Hummmm, I have the 8.3 with a MT647 & 4.10 rearend, What do I need to know about that setup?
As far as I know, the 647 is pretty similar to the 643, making it -in my mind- a pretty solid setup. I have an MT643 in my bus, and I am happy with it. Paired to an 8.3 makes that a real nice setup.
I'm assuming you probably are able to cruise at 65-70 with a nice low RPM?

John
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Old 07-13-2018, 09:34 AM   #9
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As far as I know, the 647 is pretty similar to the 643, making it -in my mind- a pretty solid setup. I have an MT643 in my bus, and I am happy with it. Paired to an 8.3 makes that a real nice setup.
I'm assuming you probably are able to cruise at 65-70 with a nice low RPM?

John
When I drove it home at WOT top speed was 67mph BUT the tach was reading 4500 rpm,, I Think it's a little off . Even at idle it reads 1200 rpm & I've tried another tack so thats brings up the next question, Where does the tach take its reading on the eng? I think I read off the alt but haven't really dug into it yet.
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Old 07-13-2018, 11:08 PM   #10
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4500!!?? Ya...you really need to check that tach. My old 6v53 Detroit "Screamer" only ran about 3300 at that speed and it was one of the highest winding (and loudest) diesels ever built.


Most factory diesels explode around 4000.


You might check out a little device called the "Tiny Tach". Brick simple and very accurate.
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Old 07-14-2018, 12:19 PM   #11
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chances are the tach was replaced at some point and it either has dip switches or was getting its feed from an alternator tach output that may very well be different than what was installed at the factory.. the tach in my DTA360 was WAY OFF.. it was pegging at 4100 RPM when i got that bus.. turns out the dip switches were set incorrectly for a flywheel that had many less teeth on it. so it was reading high.. when i set the switches o nthe back of it.. works perfect..

thats navistar, im not sure how Crown gauges get their signal.. navistar just has a hall effect sensor on the flywheel...

-Christopher
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Old 07-14-2018, 04:30 PM   #12
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chances are the tach was replaced at some point and it either has dip switches or was getting its feed from an alternator tach output that may very well be different than what was installed at the factory.. the tach in my DTA360 was WAY OFF.. it was pegging at 4100 RPM when i got that bus.. turns out the dip switches were set incorrectly for a flywheel that had many less teeth on it. so it was reading high.. when i set the switches o nthe back of it.. works perfect..

thats navistar, im not sure how Crown gauges get their signal.. navistar just has a hall effect sensor on the flywheel...

-Christopher
Yea Tried different switch positions lowest I got for idle was around 1000, That was trying 2 different tachs so it has to be the sensor on the motor.
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Old 07-18-2018, 03:59 PM   #13
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Short answer: you do NOT want an Allison AT545 transmission - it freewheels down hills and overheats going up.
What about an Allison MT643?
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Old 07-18-2018, 04:01 PM   #14
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Quote:
Originally Posted by johnbloem1974 View Post
Exactly! The AT545 does NOT have a lockup torque converter, so there is no mechanical connection to the engine, only a fluid coupling. Very minimal engine braking, with lots of slip and wasted energy going up hills.
An MT643 is a good solid 4-speed, the 1000 and 2000 series are solid overdrive 5&6-speed trannys and the MD3060 is a very solid 6-speed transmission. *However* if you want to use the full capabilities of them, make sure 6th gear is unlocked as some of them have it locked out.

My dream setup would be a 250+HP DT466 or a Cummins 8.3 mated to an MD3060 transmission with around a 4.11-4.38 geared rear end!

John
There is the answer to my question. Thks!
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Old 07-18-2018, 04:21 PM   #15
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Quote:
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What about an Allison MT643?
Locking torque converter, much better than a 545.
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Old 07-18-2018, 08:20 PM   #16
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I have heard the same thoughts on the AT545 that have been echoed here, and I've owned two buses with them. (Even while trying to avoid, the rest of the bus configuration and prices was too good to pass up)

With that, I have had only one problem with one of them (and even then, it was only an almost-problem). This was a bus with a T444E and an AT545, and on one one of the steepest hills in San Francisco it was steep enough that I could only creep up the hill at .5mph. I was afraid I was going to have to back down and go around, but i didn't. A lockup converter wouldn't have changed anything here, as it was a simple function of the converter stall speed. Besides that, I had zero problems with the bus at all, over ~10k miles on mostly flat stuff. ... The other bus (my current one) is a DT466E with an AT545. I drove this from St Louis to San Francisco and went down i70 in Colorado- the engine braking was plenty here. Since I've taken it to Burning Man and came back up and over HWY 50 East of Tahoe. This was "inconvenient" but not really a big problem. I'm not sure what everyone's expectations are as far as being able to go the speed-limit up every grade on the major interstates, but I was always at least as fast as the Trucks in most areas. There were a few where they would catch me on a mild hill but I would catch them on a steeper one etc.

The main argument I hear is that a lockup converter will help with mileage, and while I "know" that to me true, in the flying-bricks that we have, I think there are things that have a *much* larger effect on mileage. I delivered a calculated (accurate) 9mpg on both of those long trips, achieved by setting the cruise control at ~53MPH. The wind-resistance curve goes straight up around there...

Anyway, I guess my point is that if the rest of the bus is exactly what you want, don't let the AT545 scare you. Unless you're going to do some major tuning of the engine, it's built to handle the torque you're putting out, and should perform as well as any other properly-specced powertrain package.
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Old 07-18-2018, 09:04 PM   #17
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If you want to buy a true mountain bus, GovDeals.com is listing a Thomas WestCoast-ER (an upgraded version of the Saf-T-Liner) from Rim Of The World USD in Southern California, high up in the San Bernardino mountains by Lake Arrowhead. This bus has a retarder (Cummins 8.3s can't use Jake brakes, so I guess it has a Telma instead), and sanders for the considerable snow there in the winters, advertised as the Mountain Package. I looked at another WestCoast-ER from Ramona USD before I got my bus, and it had disk brakes all round and full air suspension, so they can be nicely equipped if the district wants all the bells and whistles. Rim Of The World has always had a good reputation for maintenance and upkeep, so it may be a good 'un. Definitely worth a look.

My bus was from a mountainous district in the California Sierras, so it has Jakes and the big HT transmission that locks up in 2nd, 3rd and 4th. It makes mountain driving a lot less stressful, knowing that I can descend almost any grade without touching the wheel brakes at all. I've come all the way down Cajon Pass and the Grapevine Pass at about 38 MPH in 3rd with both cylinder banks' Jakes hammering away, just like the big trucks. Fun!

John
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Old 07-19-2018, 10:35 AM   #18
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Oops, I just reread the GovDeals posting, and it says that the engine needs repair. Sorry! I guess this bus is not quite the deal I first thought it was. Too bad. A WestCoast-ER is a nice bus otherwise (assuming its engine works), and any bus with a Telma or Jake is worth getting.

John
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Old 07-19-2018, 11:09 AM   #19
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I have 2 busses... they both had AT545's.. one of them I drove around 18k. with many trips along the mountains of the east coast... never felt unsafe going up or down...



second bus I drive around 15k or so on its AT545. and samne thing never felt unsafe in the mountain ranges east of the missisippi..



both AT545's have died.. one bus has had an allison 1000 for a year (raised my fuel MPG from 8-9 to 11-14 and the engine instead of overheating in the summer mountain drives.. runs below 200 most of the time...



the other bus is getting an MT-643. (project in progress).. will report back its differences once I get it done./..


-Christopher
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Old 07-20-2018, 10:54 AM   #20
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I would echo all of the comments in regards to transmissions.

The AT-500 series of transmissions were more of a price point choice unit. Operators would spe'c that transmission for buses that were not going to be used on trips or hill routes. For a bus that was only going to drive on surface streets with very few grades up or down at speeds of less than 35 MPH the need for a transmission that cost extra $$$ wasn't a choice. The AT-500 series of transmissions are not a bad transmission for what they are. A lot of people who have converted a bus that has that transmission have been able to travel many trouble free miles. The thing is they just are not a very good choice if you are going to be doing a LOT of highway miles and/or a LOT of grades up or down.

The biggest thing to consider is the engine.

For whatever reason, regardless of what the HP/Torque numbers might say, a V-8 engine is not going to perform as well going up a hill as an I-6 engine of the same HP/Torque rating. The inline engines just pull hills better.

When it comes to pulling hills cubic inches are important as well. A Cummins 5.9L/6BT/ISB of 250 HP is going to have a torque rating several hundred pounds less than a 250 HP Cummins 8.3L/6CT/ISC. An IHC DT530 is going to out pull an IHC DT466 of the same HP rating.

210 HP is not going to be as good as 250 HP. 250 HP is not going to be as good as 265 HP. And 265 HP is not going to be as good as 325 HP. The 210 HP is not a bad choice and it will get you where you need to be going. But 325 HP will get you there without having to get into the lower gears.
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