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Author Topic: Teach me about Jake Brakes  (Read 4149 times)
belfert
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« Reply #15 on: November 02, 2007, 10:22:42 AM »

If the engine is loafing in the lower part of the RPM range, you won't get as effective retardation.

Try selecting a lower gear, get the revs up higher and then try the Jake.

I have a B500 with my Series 60.  The tranny downshifts one gear automatically any time the Jake activates.  I'll have to try downshifting manually another gear the next time I get to a long grade which will probably be next fall.
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DrivingMissLazy
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« Reply #16 on: November 02, 2007, 01:09:59 PM »

If the engine is loafing in the lower part of the RPM range, you won't get as effective retardation.

Try selecting a lower gear, get the revs up higher and then try the Jake.

I have a B500 with my Series 60.  The tranny downshifts one gear automatically any time the Jake activates.  I'll have to try downshifting manually another gear the next time I get to a long grade which will probably be next fall.
My goal is always to keep the rpm above 1800 and below 2300.
Richard
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« Reply #17 on: November 02, 2007, 03:39:57 PM »

On the B500, there is a programming that has automatic transmission down shift with the Jake Brake.  You can program it to down shift one, downshift to 4th, downshift to 2nd, or just turn it off for manual selection.  Personally prefer manual selection.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
superpickle
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« Reply #18 on: November 02, 2007, 04:17:21 PM »

Oki Doki, that tells me that If i want Jakes, I get a Bus that Already has them... To much work to Retro fit one  Sad

Good question.. Thanks...  Grin

Paul...
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belfert
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« Reply #19 on: November 02, 2007, 05:17:28 PM »

Oki Doki, that tells me that If i want Jakes, I get a Bus that Already has them... To much work to Retro fit one  Sad

Not sure why you think this.  You can at times find used Jakes for a Detroit at less than $1000 plus labor to install. 

Only newer buses with electronic transmissions and DDECs will automatically downshift, but it just means you downshift manually.
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belfert
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« Reply #20 on: November 02, 2007, 05:27:43 PM »

On the B500, there is a programming that has automatic transmission down shift with the Jake Brake.  You can program it to down shift one, downshift to 4th, downshift to 2nd, or just turn it off for manual selection.  Personally prefer manual selection.  Good Luck, TomC

Hmm..  The local Detroit/Allison dealer said nothing could be done about some issues I was having with the interaction between the Jake Brake and my Allison with cruise on.

When the cruise and the Jake are both on the DDEC will activate the Jake brake whcih downshifts the Allison.  The problem is the cruise will activate the throttle again less than two seconds which causes the Allison to upshift.  The cycle then repeats within two seconds which causes the Allison to downshift again.  This repeats 5 to 10 times in some case which is really hard on the tranny.  The fix is to turn off the Jake when using cruise.

The dealer failed to mention the option of not having the Jake cause the B500 to shift at all.  Not that I really want this option as I can see forgetting to downshift.  I'm not realy happy with this Detroit/Allison dealer, but I don't have a lot of other choice for Allison work.
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niles500
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« Reply #21 on: November 03, 2007, 01:47:31 AM »

Here is the whole enchilada - FWIW

http://209.85.165.104/search?q=cache:X5Y1IIaFK9QJ:rvtechstop.com/articles/accbrk.pdf+Jake+world+cruise+DDEC+downshifts+Allison&hl=en&ct=clnk&cd=2&gl=us
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« Reply #22 on: November 03, 2007, 07:57:27 AM »

Call me old fashioned, but....

I prefer to make the decisions about which features engage at what time and under what conditions.

And if a feature is not in immediate use, it will be turned off.

The Jake's job is to engage when you lift throttle. The cruise control lifts throttle, the jakes engage, unless it has been programmed with sufficient speed differential between cruise speed and when the Jakes should engage. Sounds like someone who didn't know what they were doing has zeroed the setting. 2 mph/3kmh between cruise setting and Jake engagement lets you use the Jakes with the cruise without too much interference betwen the two.

As for leaving the Jakes turned on all the time, when the time comes for that obscure disaster that having the jakes engage and retard the drive wheels promotes a rear slide when you suddenly lift throttle in reaction to something ahead, because your habit has been to leave them on....

All that stuff that will give limited traction, Rain, wet leaves, winter conditions, sand or gravel on the road, worn cement in the rain, orange peels, dead frogs, locusts, cow poop, etc, that we won't be thinking about and remember to shut the Jake off.

There have been innumerable accidents, often involving leaving the road, that have been contributed to by the driver leaving the Jakes turned on under less than ideal road conditions, in both crowds, tractor trailer and passenger coach.

As for forced downshifts, having the electronic transmission mind its own business gives you more flexibility in choosing a downhill speed. I've driven them both ways, and the ones that dive for a heavy downshift to 4th or 3rd will not ease on down a more moderate hill. You can't get a balance between the Jake stages and the gear that the dumb thing lurches into. End result, you run faster or slower than desired, or your passenger hollers at you to quit it, or thinks it, if you have said passenger trained to keep their mouth shut while you drive.

We build our own coaches because we are not content with the ideas of others. Why would the programming of our drivetrains be any different?

Do it YOUR WAY!!!!

happy coaching!
buswarrior

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akroyaleagle
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« Reply #23 on: November 03, 2007, 06:38:32 PM »

Richard,

I've always set my Jakes with the engine running and at operating temp.

Others,

I do not have DDEC in my Eagle but I have driven many tour buses that had Series 60's and B500s and they interacted just like my Eagle with the 8V92 and 740.

My Jake doesn't activate until the cruise drops out when above the set speed.

The cruise doesn't know the Jake is on, it only knows to come on and drop off according to the selected speed.

The Jake doesn't know anything about cruise. It only knows the cruise has released the throttle lever and it should activate. When the cruise pulls the throttle lever, it causes the Jake to think you have given more fuel and it quits.

If your Cruise is hooked up to the linkage somewhere downstream of the throttle lever, change it so it only pulls the fuel arm and not the whole linkage.

The only time I would turn off my Jakes would be when the road is slick as BK pointed out.

My theory was and is, make everything as automatic as possible. None of us will ever get any younger or have better memory.

Hope this helps
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Joe Laird
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DrivingMissLazy
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« Reply #24 on: November 03, 2007, 06:43:44 PM »

Quote
The Jake's job is to engage when you lift throttle.

I never liked to drive like this. Many times on the highway you may need to lift the throttle, but do not really want to slow down. Like going down a slight slope.

I never turned the Jake on unless I actually wanted braking action. Otherwise it was switched off.
Richare
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« Reply #25 on: November 03, 2007, 09:57:45 PM »

10-4 Richard, that's what I do.

Not turned on unless I want it on.

The brakes work great in a panic stop.

Put the myth to bed.

Believe it or not, the Jakes won't shorten a panic stop.

Figure out the horsepower potential of the brakes on your coach versus the horsepower potential of the Jakes and you'll see the Jakes generate a drop in the bucket.

Safety demands facts, not opinions.

happy coaching!
buswarrior
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Brian Diehl
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« Reply #26 on: November 04, 2007, 07:13:27 AM »


Believe it or not, the Jakes won't shorten a panic stop.


Braking horsepower aside, any manual transmission will be unable to keep up with the rate of decceleration and you'll end up with no engine braking to help.  I found this also to be true when I was running my HT 754 allison automatic. 

The only caveat I have to this is when trying a hard stop while going down a 6-8% grade at 60mph.  I had to do one of these and found that manually downshifting the tranny to as low of a gear as possible did bring the engine in to play for a little bit.  I'm sure it helped some.
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lyndon
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« Reply #27 on: November 04, 2007, 08:32:45 PM »

I don't have a Jake on the bus (yet), but from my trucking days, I hope I can provide some insight into using one. Anyone experienced with a Jake on a standard knows what happens when you forget to switch it off before leaving the driver's seat. (Engine stall, if you are wondering). It happens because it's just as easy to forget it's on as to forget it's off.

Consequences of forgetting it's on?
  • Leaving the driver's seat? Stalls, as noted above.
  • Emergency situation, road conditions aren't great? Big trouble!

Consequences of forgetting it's off?
  • None. Just reach over and turn it on when you "need" it.

In the interest of safety, I have three points to make:

1. For the above reasons, I strongly agree with the posts about driving with it off until you want to use it.
2. Never depend on the Jake to replace your service brakes. If you can't stop safely without it when going down a hill, you are in too high a gear (and going too fast.) If you can't stop safely without it on a flat surface, you are going too fast.
3. The Jake is a great addition, especially in mountainous terrain, and I would recommend installing one. But when you consider it a necessity, beware! You are one short-circuit, broken wire or bad connection away from disaster.

My opinion, FWIW, but hopefully, food for thought. Do it your way, of course, but always be safe.

Don

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Don
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TomC
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« Reply #28 on: November 04, 2007, 09:26:47 PM »

In my opinion, and this from 21 years on the road, a Jake brake has but one use-that's to provide enough engine braking in the proper gear at the proper speed to hold back your vehicle at speed so you don't need to use (or very lightly) the service brakes when descending a long grade.  The reason- then if you do get into an emergency stopping situation on the way down the grade, your brakes will be relatively cool and provide the braking power to stop you.

Using the Jake brake around town to slow you down at the signal, using the Jake brake around town just to make noise is not what it is for (course you can do what you want, and there are some drivers that don't consider others).  Good Luck, TomC
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lyndon
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« Reply #29 on: November 04, 2007, 10:14:18 PM »

Quote
In my opinion, and this from 21 years on the road, a Jake brake has but one use-that's to provide enough engine braking in the proper gear at the proper speed to hold back your vehicle at speed so you don't need to use (or very lightly) the service brakes when descending a long grade.  The reason- then if you do get into an emergency stopping situation on the way down the grade, your brakes will be relatively cool and provide the braking power to stop you.

Using the Jake brake around town to slow you down at the signal, using the Jake brake around town just to make noise is not what it is for (course you can do what you want, and there are some drivers that don't consider others).  Good Luck, TomC

Wise words, TomC.

Living near the Rockies, almost every truck around here has a Jake, and most drivers use them for around town (illegally, I should add, due to noise bylaws). The reason? To save wear and tear on their brakes, they say. When I owned trucks and had to pay for the wear and tear, I never found a need for the Jake around town. When you learn to watch traffic patterns far ahead, anticipate traffic signals and control you speed accordingly, service brakes are used only sparingly in any event.

Cool breaks on a long downgrade? That's exactly the goal.

I just realized that I may have strayed from the original purpose of this thread; my apologies! Learning about the mechanical issues in buying and installing a Jake is why started reading this thread in the first place.

Don
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Don
1988 MC-9
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