Downhill Grades With A Bus

[Rudy]

I would like a Jake Brake. I think it would make me a Broke Bloke though.

I'll be lucky to have money for diesel which will make this Joe Go.

[Headache]

Rudy, as a general rule of thumb using the same gear down as up is a good gauge but there are some caveats worth mentioning.

First is the most important of all; if you are unsure about stopping DON'T MOVE until you have satisfied yourself that you have adequate braking for what you want to do. If you don't then make the mechanical adjustments and find an alternate route. Lack of experience and/or education in dealing with emergency braking will be your most important indicator in decision making here.

As a commercial driver it was damn near a requirement that if I lost my brakes and the motoring public was threatened that it was my duty to crash my rig to save others. This included driving off a cliff to certain death if it would save lives. Don't put yourself in that position.

If you have more motor than you have in brakes you may find yourself in trouble. If you ever have any doubts drop to the next lowest gear BEFORE you crest that grade going down and err on the side of caution if you are uncomfortable/inexperienced with downshifting while heading down a grade.

You must also consider the length of the grade as even air brakes will succumb to friction and fatigue the longer the grade. Weight and gravity also play a HUGE factor.

I had been in a situation where I was heading down Willamette Pass(OR-58 ) in Oregon. It was a group of us and we all stopped at the mandatory brake check area to make sure our brakes were adjusted properly. Mind you, I was a brand new CDL holder and had only been driving for a month. Since I was the "rookie", the instructors decided that I got to lead the pack down the pass.

Not long after starting down(about a 1/4 of the way) ONE brake started to smoke a little when I applied brake pressure. Not good and nowhere to stop for miles.

The smoke got worse with each application and unfortunately the only way to stop the smoke was to either stop the truck or to remove a source of fuel to the fire. In this case the only option I had according to my instructor was to ride the brakes all the way down. This significantly reduced the amount of air getting between the shoes and drums, preventing a fire from starting, at least that's what we all hoped.

I mentioned friction fatigue earlier; yeah I had some. The longer I rode the brakes the harder I had to apply them to control the air flow. By the time I hit bottom at 50mph(starting at 25mph at the top) and could pull off, my legs were cramped from clipping my toenails on the engine fan and my hands would not unlock from the steering wheel.

I found out later that the instructors made some huge mistakes in judgment that could have cost me and the one that rode with me our lives, but that's another story.

The important thing is that you make sure you have all the tools necessary to stop, before you go.

An engine retarder is an excellent option when used appropriately. I'm sorry but I'll never be convinced that using jakes on flat ground around residential areas is necessary.

A properly working tachometer should be a mandatory piece of equipment for any vehicle with a manual transmission. I don't care how long someone has been driving, things can happen to throw a drivers rhythm off and it's good insurance to have that tach there just in case.

Rudy I know times are hard and all costs are going up making it even harder to live. However, the cost to you to purchase and have installed the above equipment(not so much the retarder but definitely the tach) will be priceless if you are ever caught in a situation where you have to make swift decisions and save lives.

[Sharkey]

And Rudy, remember also that along with all the necessary caution, your fully converted bus doesn't weigh even a third as much as a fully-laden tractor and trailer, so you don't have nearly as much to hold back on the grades as they do. The brakes on your bus were designed to work properly to keep the bus and it's passengers safe under all driving conditions. Make sure the brakes are in good adjustment and repair, and use them wisely and you will be fine.

Now, having said that, I'm really glad my bus has an exhaust brake!

[Dennis The Bus Dweller]

Headache

I may be wrong but I do believe Rudy's bus is a automatic.

[Headache]

I'm sorry, I thought I saw 4 speed somewhere. It's an assumption on my part when someone posts how many forward gears they have I automatically think manual.

[Headache]

your fully converted bus doesn't weigh even a third as much as a fully-laden tractor and trailer, so you don't have nearly as much to hold back on the grades as they do.

Now, having said that, I'm really glad my bus has an exhaust brake!

Hey now, I only had about 30,000 lbs in the wagon!

Sharkey is right but I posted my huge caution novel because I have seen a few buses smoking the zipper up so it's not impossible.

[ezrablu]

Headache...very good post on braking, thanks! I do have a 6 speed and freak myself out many times in the mountains out in Arizona, New Mexico and Colorado just in my little 5 speed pickup truck! Living around mountains for 20 years, I've seen plenty of truckers smoke their brakes and have to stop by driving off the emergency ramp into sand piles and stop barrel barricades.

I've also seen many at the bottom of a canyon along with other vehicles. Most are from back like pre-70's before they've redone all the highways to make them more mountain friendly I remember as a kid looking down the edge of cliffs while my dad drove...LOTS of crashed vehicles down at the bottom....no guard rails and roads so narrow two vehicles could just pass each other It left a very memorable impression on me and mountain driving.

Driving my bus through any mountains has been a secret worry in the back of my head ever since I got my bus. I've even told myself I will just take the "long way" around every where

[stuartcnz]

I'm sorry, I thought I saw 4 speed somewhere. It's an assumption on my part when someone posts how many forward gears they have I automatically think manual.

It's an Allison, so even though it is an automatic, it is mechanical, not torque convertor. If I'm not mistaken, so can be used manually for holding a low gear.

[Rudy]

Thanks to all for your help.

I do indeed have an Allison 4 speed automatic transmission. There is a big lever on the dash to shift it.

I talked with Bob on the phone, and assures me that my transmission will keep me at safe speeds downhill by petting it in third gear. I suppose if I was heading out west, some of those grades in Colorado might necessitate second gear.

Bob says the Allison is beefy.

I will investigate the adjustment of my brakes before I go. I am sure I'll have questions about that also. I will look into the Brake Help thread.

Thanks for all your help.

Rudy

[Rudy]

Something I am happy about is that the engine oil and filters are fresh. The transmission fluid and filter is fresh.

[Headache]

It's an Allison, so even though it is an automatic, it is mechanical, not torque convertor. If I'm not mistaken, so can be used manually for holding a low gear.

I'm a fair bit rusty in the tranny area since I was "in to" them(think Super Slide) but this sounds like my car, in that I can shift down to a lower gear and it will stay there until I put it back in "D" or a higher gear.

However, since Rudy's has no torque converter then all shifts are manual as there would be no "D" drive but no clutch is necessary(or installed), is that correct?

I remember as a kid looking down the edge of cliffs while my dad drove...LOTS of crashed vehicles down at the bottom

Reading that part sent a chill down my spine! I remember that as well, then add some vertical distance in the form of how high up bus and truck seats are.....eeewwwwww.

I will investigate the adjustment of my brakes before I go.

Very good. I am unfamiliar with your set up so as long as you never get stuck being able to shift between gears I imagine that a tach would be unnecessary.

I'm not trying to play "Chicken Little" or scare anyone, just pointing out how important it is that no matter what makes you go or how fast you can get there, it may all be pointless if you can't stop.

[Mark R. Obtinario]

stuartncz I don't know where you have gotten your information about Allison automatic transmissions but I can assure you, every Allison automatic has a torque convertor. Some have lock up convertors and some do not. But all have a TC.

If you have an Allison AT series of transmissions they do not hold back on hills very well at all when they are behind diesel engines. Normally the only way to get the engine to do any braking you need to be in the #1 hole.

If you have an Allison MT series of transmissions they do hold back on hills and they will have a lock up convertor in the top two gears.

If you have an Allison HT series of transmissions they do hold back on hills and have a lock up convertor in the top three gears. However, they go into free wheel at about 15 MPH.

And regardless of the series, if the transmission is equipped with a retarder, the retarder does not work at speeds below 15 MPH. And should never be used if the road is icy.

Knowing what you have and how they work is always a good idea before you start down a long and/or steep hill.

I have found when driving in the mountains with an automatic transmission, until one understands the capabilities of your skills and your vehicle it is best to go down the hill one gear lower than the gear you used going up. Going too slow is much preferred to going to fast.

Using the stab braking method of controlling your speed is also the preferred method of using brakes.

In order to use the stab method of braking you determine what speed you want to maintain. As your vehicle speed exceeds that speed by 5 MPH you stab the brakes to a speed 5 MPH below your determined speed. If you are using the proper gear you should not have to use the service brake very often to maintain that speed. If you have to keep using your throttle to maintain that speed you are in a gear too low. If you have to keep stabbing the brake pedal to maintain your speed you are in a gear too high.

By using the stab braking method you give your brakes a chance to breathe and dissipate heat. The whole idea of braking is to convert forward motion into heat in order to slow you down. Too much heat and you will have brake fade and possibly linings catching on fire.

Auxillary braking devices like jake brakes, transmission retarders, or driveline retarders are really nice. They reduce the amount of use the service brakes are used allowing them to be in tip top condition in time of real need. But the bottom line is every vehicle leaves the factory with what the manufacturer considers more than adequate braking capability. If used wisely there isn't a hill out there than can't be taken.

In regards to adding a jake, I would save my $$$ and spend it on something else. On a bus like Rudy's it isn't going to be cheap and isn't really worth the cost. At least I don't think so.

[kb2iaw]

Rudy, maybe ya better wear a Depends just in case the "low and slow" method don't pan out

( )

[stuartcnz]

Mark, thank you for chiming in.

The info I had on Allisons, was from a guy I work with. I asked him about them a few months ago because he used to be a bus mechanic. His explanation was much more simplistic than what you have written here, and obviously gave me the wrong impression.

[Bob]

Just speaking from my own experience and having an Allison 4-speed automatic with a 3208 cat and no exhaust brake...on really steep grades I put it in 2nd and seldom does that not keep me slow enough. If not..I apply the breaks (hard as someone else suggested) as needed to keep me under depends speeds.