Hill Driving Question

[Zephod]

As you know, I drive a schoolbus. When I learned to drive a bus, nobody taught us how to drive in hills because there just weren't any worth mentioning. Having been driving I have found some undulating terrain which I feel would be beneficial to use engine control rather than braking. The hilly bits aren't long - I don't get brake fade but I know if my foot was off the brake, the bus would get out of control very quickly and with the sharp bends, turnovers etc are a possibility.

So, I have (on both my own and the work bus) an automatic transmission. I've never even used other than D, N and R is my car let alone a bus.

How does it work? If I'm going up a hill, can I with my foot still on the gas, slip the transmission from D to say 3 or even 2? Same for downhill, while I'm braking, can I slip the transmission from D to 3 or even 2? How about when I'm back on the flat and accelerating, can I slip it from 2 to 3 or 3 to D with my foot on the gas?


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[buswarrior]

Yes, provided you don't mess with a gear that is not matched to the speed you are going.

When accelerating, take note of the fastest speed attained in each gear, that's your marker for using that gear in the other direction, slowing down.

The speed limit is meaningless when going downhill. You slow down to whatever speed you can keep it under control with a minimum of brake use. The ones following will have to be patient, that's what your 4-way flashers are for, and if they want a Youtube spectacular, you aren't going to be it today...

You must be off the brakes many times longer than on them. If you have to go back to the brake right away, you are going too fast for that slope.

Slow down some more, choose another lower gear, keep those brakes cool.

happy coaching!
buswarrior

[windtrader]

BW - Just curious about determining the max speed for each gear. in my MC8, there are color bands on the speedo that seem petty close to the shift points whent tranny is under load. The coach actually crosses over those points when flat out floored.

This may be a dumb question but does the 8V71N mated to a HT740 have governor(s) to keep motor from exceeding a specific RPM? If so, than can I run a test on flat ground in no wind conditions and stomp on the pedal until it won't go any faster. That is then the top end speed for that gear/motor combo in this coach?

I have driven it enough under full power conditions in the lower gears in manual mode and know about where it needs to shift but never really maxed it out to know the specific limits of each gear.

@Z if you are on mild rolling hills it still pays to use the manual shifting to keep the speed where you want without using the brakes much. Next time just put in lower gear from drive when you are feeling the need for more than a touch of braking is needed. You definitely need to shift down if you are needing to use brakes a lot to keep bus from going too fast.

Also, if you find the tranny is sifting a lot, hunting between gears, then put in the lower gear and that stop the hunting,

[lostagain]

Don, your 8V71 is governed at somewhere between 2100 and 2300 rpm. So yes, you can feel when you hit the governor when it will no longer accelerate. You can then memorize the top speed for each gear, or mark the speedo with a permanent marker or whiteout, or tape. Don't exceed that going down hill of course. The HT740 up-shifts smoother (manually) if you do it just before you hit the governor. And down shift it when the speed is at or below the line you marked. Most MCIs of that era didn't have tachometers.

JC

[Zephod]

Well, I put the work bus in 2 and it wasn't low enough. L worked better. I could run down the slope in L with my foot off the brake. I've taught my codriver to do that now.


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[opus]

You have an AT545 transmission.  Translated that means you pretty much have no braking abilities.  Your converter does not have lock up.

[Zephod]

You have an AT545 transmission.  Translated that means you pretty much have no braking abilities.  Your converter does not have lock up.

There are 3 transmissions commonly put on my Carpenter 3800 1994. I'll have to hunt for the transmission I'd plate.


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[luvrbus]

There are 3 transmissions commonly put on my Carpenter 3800 1994. I'll have to hunt for the transmission I'd plate.


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Post a photo of the shift tower you can tell by the shift tower or pad what transmission you have

[Zephod]

Post a photo of the shift tower you can tell by the shift tower or pad what transmission you have

Do you mean the gearstick?


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[Zephod]

My gearstick - bottom left


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[luvrbus]

You have a 543 Allison looks like to me

[Tony LEE]

Read up on "Snub Braking" and practice the techniques before you really need them.

Also "Factors affecting RV Performance" published by CAT is also worth having a look at. Free on the web

[Zephod]

Read up on "Snub Braking" and practice the techniques before you really need them.

Also "Factors affecting RV Performance" published by CAT is also worth having a look at. Free on the web

Oh, I do that kind of braking normally, downhill. I didn't know it had a name.


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[Zephod]

You have a 543 Allison looks like to me

So, not the 545 suggested earlier?

That would tie in with the sticker I had to remove that said to put the transmission in 1st or 2nd for engine braking.


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[opus]

For the year 1994, I still say its a 545 until you look at the plate and differ.  The 540/542/543/545 are all basically the same.  Either way, it is without a lockup converter.