How to get an AT545 down wolf creek pass CO...?

[Shef]

You guys kill me! Glad to hear of relavent mtn driving stories/tips. Had no idea a bus could do 90 downhill with a 545!? Well, with my additional wind resistance I don't think I have to worry about much going down monument hill anyways.

[karrlot]

You might try sails or a drag chute.

[Elliot Naess]

Amazing. A generation gap, I suppose, because... three pages, and still no mention of...

https://www.youtube.com/watch?v=X6LzWZYWpOU

[turf]

ahhh, the long lost art of redneck rapping. trucker songs

[EastCoastCB]

Originally Posted by Tootalltechie

Is it possible to put a lock-up torque converter on a AT545 transmission? I have a 1974 chev bluebird with a 350cid and a at545. Driving home from where I bought the bus I had at least two 9% or 10% grades. I down shifted on the hills making sure I stayed in the speed range of the gear.

Sent from my SM-G530W using Tapatalk

Negative on the lockup TC. The 545 ain't got one.

[Shef]

Great ditty!

[Versatile]

Originally Posted by cowlitzcoach

I will be one of the first ones to say the AT540 series of Allison transmissions were built more to a price point than anything else.

As a consequence a lot of shortcuts were involved when designing and building it.

That doesn't mean it is a bad transmission. I have known some to go well in excess of 300K miles without anything except for regular fluid and filter changes. I have had personal experience with that transmission on some pretty steep hill routes. We never had any problems going up or down hill other than we used up more brake lining over a year's time than we had previously.

The one thing that will kill an automatic transmission quicker than anything else is to get it hot. And it will if it doesn't have enough cooling capacity.

In September of 1990 our district put into service ten TC2000 12-row buses with the Cummins 5.9L 190 HP/AT545 power package. Three things became very clear within the first week.

• The transmission cooler was inadequate. The first afternoon I went up the hill on the route I had been on for more than five years with a Loadstar chassis bus with the MV404/AT545 I knew we had a problem. I went up the hill like I had for five years. Before I got up the first mile the transmission temperature was well out of the green and heading for the red.
• The new power package did not hold back on the downhill as well as the old one did. I headed down the hill and geared it down to 2nd like I had been doing with the Loadstar. In the Loadstar that meant I went down the hill with virtually no application of the service brake at speeds of about 25-30 MPH. In the TC2000 that meant that even with stab braking I was doing about 45 MPH.
• The brakes on the new buses were not adequate. Come to find out the rear brakes had 20/20 air cans when the spe'c was supposed to be 30/30 air cans. 50% more braking chamber capacity makes a HUGE difference in braking ability.

Over the next few weeks all ten of the buses went back to the dealer for extended stays as they upgraded everything.

When the buses came back with 30/30 air cans on the rear brakes, with the first application of the brakes when leaving the bus garage I knew I had a LOT more braking ability.

The new transmission cooler was large enough that it almost completely covered the front of the radiator. Even on the hottest days the transmission temp never ever went much above halfway in the green scale.

And I learned that in order to get any engine braking I needed to lock it down into 1st gear before I headed down the hill. Locked into 1st gear I could maintain an average of 25-30 MPH with stab braking while going down a 12% grade.

This long winded reply is all to say that if you are prepared properly there is no reason to think you will have any problems going up or going down any pass in the country as long as you drive smart.

On the way up the hills, when you start to see your temperatures rising slow down before you have to stop and cool down. Dropping down a gear and slowing down an addition 15-20 MPH will take less time to get up the hill than if you have to stop for half an hour cooling things down.

On the way down the hills, lock the transmission down into the lower gears before you break over the top of the hill. Even if it means locking down into 1st gear and moving very slowly down the hill with your flashers on, it is better than learning how to use the runaway ramps.


Good luck and happy trails to you!

Great post. Totally agree. This very much. "as long as you drive smart."

[cadillackid]

cowlitz - this is a question along the same lines since we are talking aboiut brakes..

in orlando on thursday as i left to come to ohio, a crash happened right in front of me.. I was in RedByrd which has hydraulic disc brakes.. I hit the brakes hard.. not hard enough to engage the ABS. but hard enough anything left on a seat was now on the floor wit ha bang... I stopped with extra braking power to spare...

everyone goes on about air brakes are better blah blah...
when I practice heavy stops oin my DEV bus which are air drums.. I am smoking 4 rear tires when I still can press harder and grab more from the front brakes and gain more stopping power..

I was told with air brakes that 80% of my stopping power comes form the rears unlike a car... yet I sure had MUCH more confidence in those hydraulic disc thursday than I wouldve in my air brake bus.. im quite certain I wouldve been part of the pile-up had I been in the DEV bus.. with air brakes.. are my air brakes broken? or is it just the rears lock up easier on them?
-Christopher

[DoubleO7]

You likely have less pounds per square inch in contact with the road. Plus bus tires are not too grippy rubber to get the most miles out of them.
Less psi on the road and the rears lose grip of the road and immediately skid.
At the same instant your front brakes become your prime stoppers.

[dredman]

Originally Posted by cadillackid

everyone goes on about air brakes are better blah blah...
when I practice heavy stops oin my DEV bus which are air drums.. I am smoking 4 rear tires when I still can press harder and grab more from the front brakes and gain more stopping power..


-Christopher

I have had EXACTLY the same experience with my brakes. I bought into the "air is the only way" mantra also, and was disappointed my new bus had hydraulics UNTIL I drove the bus. I think the difference is night and day. The hyd-braking is more like that of a car than the air brakes offered - smooth and confident braking rather than the ON/OFF of the air brakes. Don't get me wrong, they both stopped the bus, but one smacked your face into the dash?

[cadillackid]

I understand the concept of weight transfer.. I used it in reverse when I raced cars.. I typically adjusted my suspension for the momentum of my suspension to bottom (most weight on rear tires) when I was between 60-100 feet into my run (most torque on the tires at that point)..

but if it was just weight transfer.. I sure shouldve been screamin the rear tires on the bus thursday.. or at least triggering the ABS.. ( I know what the ABS feels like in it because I played with it in the snow over the winter in ohio)..

I had a nice even stopping experience and quick..

on the DEV.. I feel like my rear wheels are useless in braking.. kind of that empty pickup truck feel only somewhat worse.. after all skidding tires are not doing alot of stopping.. they are merely telling anyone behind you that you are trying to stop (with a smoke screen)...

I also dont have any control over that rear end if the wheels are stopped.. sure i can press harder and get some more out of the fronts.. and in a perfect world i was going 100% straight when i hit the brakes and the rear would continue that path. in the REAL world chances are that rear is going to swing one way or the other.. esp if I was in a slight curve before slamming the brakes..

with air if I rapid pump the brakes to simulate ABS and control the rear i soon find im losing air pressure quick.. which means not as much pressure to the fronts or rears and less stopping power..

maybe my air brakes are misadjusted? not proportioned correctly?
-Christopher

[turf]

my 2 cents is that one system is not better than the other, only different.

i'd bet that disc brakes are at their physical capacity on a medium duty truck and the air brakes are more capable for larger weight handling, and at the bottom of their usefulness on a medium duty truck weight range.

[cowlitzcoach]

Originally Posted by cadillackid

cowlitz - this is a question along the same lines since we are talking aboiut brakes..

in orlando on thursday as i left to come to ohio, a crash happened right in front of me.. I was in RedByrd which has hydraulic disc brakes.. I hit the brakes hard.. not hard enough to engage the ABS. but hard enough anything left on a seat was now on the floor wit ha bang... I stopped with extra braking power to spare...

everyone goes on about air brakes are better blah blah...
when I practice heavy stops oin my DEV bus which are air drums.. I am smoking 4 rear tires when I still can press harder and grab more from the front brakes and gain more stopping power..

I was told with air brakes that 80% of my stopping power comes form the rears unlike a car... yet I sure had MUCH more confidence in those hydraulic disc thursday than I wouldve in my air brake bus.. im quite certain I wouldve been part of the pile-up had I been in the DEV bus.. with air brakes.. are my air brakes broken? or is it just the rears lock up easier on them?
-Christopher

Air brakes have several advantages over any wet brake set up. Among them is they can accommodate larger braking surfaces and dissipate heat more readily. Any wet brake system will transfer some heat into the fluid which will degrade braking efficiency.

Wet brakes also tend to degrade just sitting. The fluid will absorb water which lowers the boiling point of the fluid. Also, the water tends to rust parts in the cylinders and pistons causing them to fail.

As far as braking ability, I have always found the wet brakes to stop much quicker than air brakes at slow speeds. But the wet brakes don't have the reserve capacity you want when going down long steep grades with full loads.

Going downhill empty on a wet road could almost always end up locking up the rear brakes on wet brake equipped buses. Newer buses with four wheel disc and ABS do not have the issues we had back in the day with four wheel drum and no ABS when it comes to locking up. The ABS equipped buses will stop shorter and without locking up. That is a fact.

But I would rather have air brakes with a spring brake emergency/parking brake than the best four wheel disc ABS system out there.

[EastCoastCB]

I was gonna ask if you have ABS, Chris?

[dan-fox]

And would the story be any different with a rear engine bus, where the weight distribution is very different?

[JDOnTheGo]

Originally Posted by Shef

What concerns me is going down the westbound side of Wolf Creek pass, into Pagosa.

Howdy Shef,

I've been over this pass a couple times in a car and twice in a diesel pusher motorhome with an engine brake.

This is a VERY serious mountain pass and, if I were in your shoes (and equipment), I would not risk it. I'm guessing at your direction of travel but I would likely go around via Espanola, NM. Highway 285 is a good road as is 84.

If you choose to go over Wolf Creek - note that there are two or three runaway vehicle "ramps".

Best of luck no matter which route you take!

[spenceronehalf]

Get a chain and a friend to dive behind you braking.


Sent from my iPad using Tapatalk

[JDOnTheGo]

Originally Posted by Shef

Hello all, I'm looking for some advice on a situation I've gotten myself into.

So??? What happened???

[Iceni John]

I know this trip will be the bus's last before you put it out to pasture, but it only takes one bad hill to make a mess of everything. My suggestion is to install a trustworthy transmission temperature gauge, which is something critical for a non-lockup like yours - I recently changed out my gauge for a Speedhut which works well. I also have a dual air pressure gauge that I connected to the spare ports on my E6 treadle valve: this gauge shows me the separate front and rear brake application pressures. If they are increasing for any given speed and gradient, you know your drums are getting hot and expanding, and it's time to pull over to cool off.

Another idea is to climb and descend in the middle of the night or the early wee hours, when the air is cooler and there's much less traffic. Just make sure your lights, especially the rear lights, are good and bright.

If you ever decide to drive your bus again in the mountains, try to find a used take-off Telma retarder from a scrapped school bus. (Doesn't CO mandate that all school buses there must have a supplementary brake?) One version fits on the rear axle (Focal?), and another version goes around the driveshaft. As long as your alternator can provide enough power for it, you can go down any hill without using your brakes much. It makes no difference if your transmission is a lockup or not. I'm even tempted to fit a Telma to supplement my Jakes - you can't have too much braking!

Good luck, John

[Brad_SwiftFur]

As a professional driver - who learned the hard way how *NOT* to descend a steep grade in a fully loaded truck (not to worry, the trip was completed safely) - I don't think you'll have any problems negotiating this grade. You are conscientious of transmission temperatures going up, and brake fade coming down.

Just keep speeds reasonable and use the stab braking technique. At speeds under 30 or so, you're very unlikely to fade the brakes. What usually overheats the brakes is simply riding them constantly, all the way down the hill. I've descended countless hills using low gear and stab braking and (after that first learning experience) never cooked the brakes.

In most air brake systems, your "emergency brake" *IS* the parking brake. It uses the same drums, brake linings, etc. as the service brakes. It is simply a separate portion of the brake chambers.

I would take this chance to add that if you stop with hot brakes and set the parking brake, there is a good chance the brakes will "stick" as they cool and you may have a difficult time getting them to release (does this sound like the voice of experience talking?) Might be wise to release the brakes and let the bus roll a few inches every few minutes to prevent this. Anyone else with experience on this care to chime in?