Reply
 
Thread Tools Display Modes
 
Old 10-22-2016, 09:59 AM   #1
Bus Nut
 
Join Date: Jun 2011
Location: KANSAS CITY
Posts: 690
Exclamation Why you don't want the Allison AT545 Transmission in the mountains.

In mountains that are knarly you need braking assistance. This bus surely didn't have the AT545. I am just sparking conversation about the position you could end up in. On this bus the JAKE BRAKE failed.

12 Dead, 18 Injured As Bus Goes Over Cliff In Cariblanco | Q Costa Rica

12 Dead, 18 Injured As Bus Goes Over Cliff In Cariblanco

the driver was not able to engage engine compression to slow down the bus as it went down the steep hill, veered onto the oncoming lane
__________________
Former owner of a 1969 F600 Skoolie.

1998 Ford B700 Thomas body 65 passenger. 5.9 Cummins 12 valve with MT643 Transmission 123,000 miles.
Versatile is offline   Reply With Quote
Old 10-22-2016, 10:30 AM   #2
Bus Crazy
 
turf's Avatar
 
Join Date: Apr 2013
Location: Colorado
Posts: 1,599
Year: 1993
Coachwork: bluebird
Engine: 5.9 Cummins, Allison AT1545
Rated Cap: 2
that accident is awful!

i don't think it had one (an at545) but......driving mountains with the AT545 has a learning curve. the transmission sure isn't gonna help you.

if you downshift at the top of a hill, the fact there is no lockup will soon be apparent as gravity accelerates the bus down the incline. the rpms will roar, then the transmission starts making awful noises like the metal vanes in the torque convert are snapping off, and the truck accelerates down the hill. the transmission will not hold you back!

my rule for hills with the 545, don't go any faster down than you did up. its going to annoy people behind you, but 10 tons of steel hurdling out of control is absolutely no fun. if i can only do 40 on the way up, i try to not exceed that on the way down. I stab break at 40mph, down to 30mph, and repeat.
i do downshift the trans into a lower gear, but only one that i can keep appropriate speed at. 3rd gear works if you keep it under 45 with the brakes.

the allison at545 manual states that the only thing that will slow the transmission is the service brake. downshifting won't.

going up wears out the truck, going down wears out the driver.

good luck!!
__________________
.
Turfmobile Build Thread
turf is offline   Reply With Quote
Old 10-22-2016, 12:16 PM   #3
Bus Nut
 
Join Date: Feb 2015
Location: Cincinnati, Ohio
Posts: 866
Year: 2000
Coachwork: Blue Bird
Chassis: International
Engine: TE 444
Rated Cap: 12
The bus that wrecked most likely had a manual transmission, automatics are rare in most third world countries on buses built for sale there, different story when they import our used buses because they are cheap, saw old US school buses when I was in the Dominican Republic
Kubla is offline   Reply With Quote
Old 10-22-2016, 02:14 PM   #4
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,120
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
the AT545 isnt horrid in the mountains if you drive it correctly.. yeah you gotta go slow.... 3rd or 2nd gear and it pulls down nicely..

if tyou have a 545 that is modern on a computerized engine, you can piut a switch o nthe modulator and force it down to 3rd at a faster speed by about 5 MPH over what the manual shifter allows..

but yeah for serious mountain driving a Lockup tranny is desirable..
-Christopher
cadillackid is offline   Reply With Quote
Old 10-22-2016, 04:32 PM   #5
Bus Crazy
 
Join Date: May 2016
Location: Georgia
Posts: 1,651
Year: 2001
Coachwork: Blue Bird
Chassis: IH
Engine: T444E
Rated Cap: 14
Golden rule when descending steep hills - or rounding sharp curves - or - basically anything else . . .

You can do it a million times too slow. You can only do it too fast once.
Brad_SwiftFur is offline   Reply With Quote
Old 10-22-2016, 04:52 PM   #6
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,027
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
I just started my bus up, looked it over a bit and headed home to FL from KY.
A friend caught a bit of video going down a pretty decent grade on Monteagle TN.
I was a bit nervous as it was only a few hours into the trip. The lockup TC did its job and there was no drama coming down. I had a bus with a 545, and this time around I really wanted something better.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 10-22-2016, 05:10 PM   #7
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,120
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
Quote:
Originally Posted by EastCoastCB View Post
I just started my bus up, looked it over a bit and headed home to FL from KY.
A friend caught a bit of video going down a pretty decent grade on Monteagle TN.
I was a bit nervous as it was only a few hours into the trip. The lockup TC did its job and there was no drama coming down. I had a bus with a 545, and this time around I really wanted something better.

your vid brings up a great point... basically about the difference bus size can make..

ive run the DEV down that hill 3 or 4 times now and barely even hit the brake... its a short bus vs a big full size one like yours.. my AT545 holds up just fine in a bus like that.. whereas im guessing in a large bus like yours it couldnt stand a chance..

the brakes on DEV and your bus are likely similar size..

headed northbound that 3 mile 7% (I think it is) into cinci I touch the brake now and then... on the new bus its so light that I just let off the pedal and it ran itself down the hill about 63 the whole time.. (that hill is straight so no reason to not drive that speed)...

with the new bus i fixed its trans temp gauge so it will be interesting to see as I drive it in the hills how hot the transmission gets.. around town in oghiop where its cool out of course it barely goes to 150...

-Christopher
cadillackid is offline   Reply With Quote
Old 10-22-2016, 05:25 PM   #8
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,027
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
I still tapped the brakes a bit on the way down but putting it down into "3" it seemed to stay at around 40-45 mph. Auto slack adjusters and abs on a 92 like mine are rare, but are also great peace of mind on a grade.
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Old 10-22-2016, 05:32 PM   #9
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,120
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
the DEV doesnt have ABS but does have auto slack adjusters.. my new bus is hydraulic ABS disc.. I havent played in the rain with it yet to see how it stops in a panic stop..


my main point thouigh is an AT545 in a smaller bus may just do the job fine.. whereas in a big bus its inadequete for hills..

-Christopher
cadillackid is offline   Reply With Quote
Old 10-22-2016, 05:35 PM   #10
Bus Crazy
 
turf's Avatar
 
Join Date: Apr 2013
Location: Colorado
Posts: 1,599
Year: 1993
Coachwork: bluebird
Engine: 5.9 Cummins, Allison AT1545
Rated Cap: 2
when ever i see a 7% grade sign... i turn on the 4 ways and let everyone pass me until im back down.

mount rushmore, in south dakota, has a 10% grade. want to see your transmission slip? try that one out!


i did add a trans cooler to my at545 setup and that has helped tremendously. it was like bolting on a turbo.... i got a lot more power.
__________________
.
Turfmobile Build Thread
turf is offline   Reply With Quote
Old 10-22-2016, 05:52 PM   #11
Bus Nut
 
GreyCoyote's Avatar
 
Join Date: Mar 2016
Location: Danglebury, Tejas
Posts: 310
Year: 1999
Coachwork: Blue Bird
Chassis: IH 3800
Engine: Navistar DT466E
Rated Cap: 72 passenger
The 545 isnt a world beater by any means, but it IS a fairly decent tranny for when it was developed, and for WHAT it was designed for (there. I said it). Many tens of millions of miles have been logged hauling school kids around with them, and they appear in all sorts of medium duty trucks. You dont get this kind of market penetration if you are building an Edsel. The 545 really isnt "bad". But it is old technology and getting long in the tooth. And its not made for pulling hills all the time in a 30k GWV bus.

Many of the people who roundly decry the 545 as "junk" have never owned one. Or if they did, they got it with the bus (at auction, with its socks down around its ankles) and it had 200k miles of wear. And then they refuse to use the correct, current generation fluid, they crank-up the injection pump, and then take it out on a hilly banzai run in the middle of summer without a cooler. And they wonder why there are troubles.

The truth is, its not a bad tranny. And if you have one, you would be well-advised to read the Allison service bulletins and learn to drive it and maintain it properly. It isnt idiot proof, and it does not suffer shock loads well at all. But it WILL perform to the nameplate values with basic care.

A fact I recently learned from a retired Allison engineer: full pressure on the internals (bands) doesnt occur until the input shaft hits 2400 rpm. If you run slower than this, the trans is slipping under load and under a heavy load the result is predictable. Many school districts in hilly areas found this out the hard way when they ordered taller rear-ends and set the rev limiters at 2300 rpm thinking they would save money on fuel by "better using" the torque curve instead. Those districts wrote a lot of checks to transmission suppliers.

I'm looking at upgrading from a 545 to a 643 or 3060. Not because there is anything wrong with the 545, but rather because I want a locking torque converter and something I can flog in the hills without cringing. And a couple hundred RPMs less at 60 mph would be nice too. Otherwise I'd happily stick with the 545 and call it good.

Back to the article referenced: we dont know what happened there, but if you havent mastered basic bus dynamics, that could indeed be you. So take the time to train yourself how to drive a bus, to stop a bus, and to maintain a bus before you get too far down the road. Some accidents arent avoidable, but most are.

End rant.
__________________
"You can finally say you have enough horsepower when you leave two black streaks from corner to corner"
(Mark Donohue, famed TransAm driver)
GreyCoyote is offline   Reply With Quote
Old 10-22-2016, 06:20 PM   #12
Bus Nut
 
dredman's Avatar
 
Join Date: Dec 2014
Location: Birmingham Al
Posts: 577
Year: 2003
Coachwork: Blue Bird
engine brake failed?
pedal brakes failed too?

Sounds like a shyte-driver more than mechanical/design issues?
__________________
My Skoolie Story on YouTube
dredman is offline   Reply With Quote
Old 10-22-2016, 07:11 PM   #13
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,120
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
if i do an upgrade or ruin one of my 545s.. I would likely do a 1000... it is nearly a direct drop in to a 545 size-wise and was made in SAE 2 and SAE 3 so will fit most any engine out there...

CAC even makes a TPS for it that mounts inside the bus or in the engine bay and uses a cable just like the 545 so you simply run some wires, and snap the TPS t othe existing throttle bracket... ..

I read somewhere about the 545 and the pressures... both of my busses have REV limiters set at 2600-2700 and when im on them hard they are always at about 2300 or 2400 .. esp hammering an uphill.. I keep fresh filters and fluid in them.. though I am still using the standard DEX-III that is recommended in the book..

I should probably look into some of the updated fluids..

thje other big thing people do to 545s is mis adjusted shift-cables.. or broken ones.. that will keep the line pressure low and cause issues..

on the later ones the electronic modulator relay often goes bad or the pedal switch fails (esp if schools cleaned busses by hosing them out).. that has the same effect as a broken or misadjusted shift cable... the modulator on the newer ones should engage at 65% throttle and above..
-Christopher
cadillackid is offline   Reply With Quote
Old 10-22-2016, 09:34 PM   #14
Bus Nut
 
Join Date: Jun 2016
Location: Orange County, CA
Posts: 859
Year: 1990
Coachwork: integral
Chassis: Crown Supercoach II (rear engine)
Engine: Detroit 6V92TAC, DDEC 2, Jake brake, Allison HT740
Rated Cap: 37,400 lbs GVWR
Even if you have Jakes or a Telma, you should never go faster down hill than whatever speed is controllable by the wheel brakes. In other words, you should never 100% rely on supplementary brakes to keep you at a safe speed. The extra brakes are to merely keep your wheel brakes cooler, so if you need them in an emergency they won't be already overheated and fading.

I came down Cajon Pass (a steady 6% grade) last May at 38 to 40 MPH in 3rd using my Jakes the whole way - I had to toggle between one bank and both to prevent slowing too much. I did not touch my wheel brakes at all. That's where Jakes are useful - no stress or worry, and cold wheel brakes at the bottom.

John
Iceni John is offline   Reply With Quote
Old 10-22-2016, 09:55 PM   #15
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,120
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
I'm totally if the mind of going slower..
one technique if the hill is straight and not curved is allowing speed to build to increase wind resistance.. I knew my cinci hill was straight and I have good traffi. Visibility .. so I let the. Bus run 65 knowing if I had to tap the wheel brakes it would be rare. And a short bus is light enough it wouldn't overspeed.. had I tried to keep it at 45 or 50 I'd have been in the wheel brakes a bit... so in effect with that particular grade the wind was my jake.. I wouldn't have tried to run 65 on an unknown grade or one with low traffic visibility..

Christopher
cadillackid is offline   Reply With Quote
Old 10-23-2016, 01:44 AM   #16
Bus Nut
 
Dapplecreek's Avatar
 
Join Date: Mar 2016
Location: near Christiansburg VA
Posts: 692
Coachwork: Thomas
Chassis: Freightliner
Engine: Cummins 5.9
Rated Cap: 44 or 66? 11 rows
Quote:
Originally Posted by cadillackid View Post
... to increase wind resistance....
Dapplecreek is offline   Reply With Quote
Old 10-23-2016, 03:55 AM   #17
Bus Nut
 
Join Date: Sep 2016
Location: Darrington, Wa.
Posts: 304
Year: 1994
Coachwork: Genesis/Am-Tran Tall Roof
Chassis: International, 643 transmission
Engine: DT 466ci 250hp, International
Rated Cap: 86 screaming Monsters
Quote:
Originally Posted by EastCoastCB View Post
I just started my bus up, looked it over a bit and headed home to FL from KY.
A friend caught a bit of video going down a pretty decent grade on Monteagle TN.
I was a bit nervous as it was only a few hours into the trip. The lockup TC did its job and there was no drama coming down. I had a bus with a 545, and this time around I really wanted something better.

I'm out here in Washington and I love the PRETTY DESCENT GRADE. here we can use parachutes on the backs to help slow the decent. My father comes over I 90 at the top of the pass which looks like vertical drop in his 45ft monaco with a tag axle at 10 over the limit like its a WrX soob. scares the F right out of a sane person. says the brakes don't get hot because they don't get used. its like filling the fuel tanks back up. I don't feel like I'm tall enough any more to go on that ride.
Geo Jeff is offline   Reply With Quote
Old 10-23-2016, 04:03 AM   #18
Bus Nut
 
Join Date: Sep 2016
Location: Darrington, Wa.
Posts: 304
Year: 1994
Coachwork: Genesis/Am-Tran Tall Roof
Chassis: International, 643 transmission
Engine: DT 466ci 250hp, International
Rated Cap: 86 screaming Monsters
Quote:
Originally Posted by Dapplecreek View Post
That's funny stuff tell your on that Idaho Montana fireworks pass or what ever its call Fourth of JULY Pass on I90. My Geo metro with the engine off will coast for so many miles there at 80 to 85mph. unreal.
Geo Jeff is offline   Reply With Quote
Old 10-23-2016, 08:57 AM   #19
Bus Geek
 
Join Date: May 2009
Location: Columbus Ohio
Posts: 12,120
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
ha! thats too funny.. I could imagine someone actually using parachutes on an RV just to be funny...

of course the stuff I have out east here is whimpy compared to out west... I remember traversing the rockies as a kid in our scout.. the bets ever was leaving death valley at 6am in July.. it was 98 outside when we left.. we headed right up into the mountains to go 4 wheeling... by 8am it was snowing on our windshield... Love that quick contrast as we ascended the mountains..

-Christopher
cadillackid is offline   Reply With Quote
Old 10-23-2016, 09:22 AM   #20
Bus Geek
 
EastCoastCB's Avatar
 
Join Date: Sep 2014
Location: Eustis FLORIDA
Posts: 19,027
Year: 1999
Coachwork: Thomas
Chassis: Freighliner FS65
Engine: Cat 3126
Rated Cap: 15
Quote:
Originally Posted by Dapplecreek View Post
You make some great meme material!
__________________
.
Roll Your Own Build Thread
EastCoastCB is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3

All times are GMT -5. The time now is 12:16 PM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
×