In a couple of weeks we are heading west from the Milwaukee area into Gillette WY. The route doesn't take us through actual "mountains", with flattestroute.com showing the maximum downhill grade at about 4%. However, I want to get some feedback on what to expect from our bus as we wind down the highway, since to me reading that something is a 4% grade doesn't mean much - at least not till I'm driving it and then it's too late to ask.
Our 4108 has a 4-speed and no Jakes. Brakes are in good condition and have been inspected/adjusted a couple of hundred miles ago. I'm aware of the need to downshift prior to starting downhill. I've read all the posts on steady braking vs. stab braking. Not trying to reignite that controversy.
My basic plan is to downshift into 3rd before cresting the peak, then use stab braking to keep the speed down as necessary.
Anyone have advice regarding what gears/speed combination is recommended for various percent grades? Any other tips for safely negotiating downhill grades? Am I worried about nothing with 4% grades?
4% grades are common even in the Cheese state. Albeit of fairly short duration. At 6% you know you are climbing. Our first was a 4108 and third gear climbs were frequent. Sometimes down to second gear. And a very few to first gear. For instance Wolf pass in Colorado has a hairpin turn towards the start of the eastbound climb, had to go to first. Then caught a break of slight change in angle and was able to run second gear the rest of the way to the top. Speed in second varied between 18 -25 MPH. The old rule of thumb gear up the hill was gear down the hill.
The biggest problem with Jake brake on a Buffalo is the bulge in the engine door.
Enjoy and don't be afraid of the hills just careful,
Bill
Off the brake far more than on the brake, no matter the hill.
Otherwise, slow down more, while you still can, and grab another gear lower.
The trouble with all the old sayings, you have to have experience to know what they mean...
The coach brakes can only take so much heat, before they won't slow the coach anymore. Once burned, it is permanent. The linings do not grab as well as they should anymore.
Smoke emitting from the wheel wells is definitely a bad thing...
You will be fine on 4% in 3rd, probably no brake required.
If a busnut's speed is more than 20% less than the other traffic, right lane, 4-way flashers on, and carry on. The peeps behind will just have to dealwith it. DO NOT let following traffic be any part of your decision-making as to safe descent speed.
You only get to go downhill too fast once, you may go down too slow indefinitely...
Happy coaching!
Buswarrior
With your concern, I would, and do go in the lower gears (2nd) on grades.
Once you exceed the buses capability, it's to late.
Yes it's doable.
I have no Jakes and a 740.
Alaska to Prescott and Flagstaff to Sweetgrass plenty.
But,I don't over estimate my bus or my brakes or my experience.
Know all 3 before you decide to start down in 3rd gear.
Actually driving with your flashers on is illegal in many states no matter how fast you are going. Not saying not to do it, just pointing it out.
Just the first sight I went to. I knew about CA, not the rest.
https://driversprep.com/when-should-you-use-emergency-flashers/ (https://driversprep.com/when-should-you-use-emergency-flashers/)
Quote from: somewhereinusa on June 28, 2018, 08:36:48 AM
Actually driving with your flashers on is illegal in many states no matter how fast you are going. Not saying not to do it, just pointing it out.
Just the first sight I went to. I knew about CA, not the rest.
https://driversprep.com/when-should-you-use-emergency-flashers/ (https://driversprep.com/when-should-you-use-emergency-flashers/)
Interesting, but obviously confusing in the way this plays out in real life. Seems like even in states that generally don't allow driving with 4-way flashers active many still allow it if alerting to a dangerous situation. Wouldn't driving slower than traffic up/down a steep grade be the definition of just that - a dangerous situation.
In Wisconsin (where according to that site the practice is legal) semi drivers will turn on their 4-way flashers whenever they encounter sudden slow downs or traffic obstructions. Seems like they are trying to let drivers behind them know that something is going on in front of them, which is a good idea since drivers behind them can't see around the semi.
eagle19952 - What's the upper speed you can maintain with your 740 in 2nd gear? In our 4108 with the 4-speed, 2nd maxes out at about 30 mph.
In all states and provinces, in actual real life, 4 ways are used by trucks and buses going less than 40 mph, to warn others of sudden slow downs and traffic hazard, in bad weather, etc.
JC
In all states and provinces, in actual real life, 4 ways are used by trucks and buses going less than 40 mph, to warn others of sudden slow downs and traffic hazard, in bad weather, etc.
JC
All good advise. I live in northern Arizona 6% to 7% grades are the norm. Stay in right lane, gear down before you start and enjoy the scenery and don't worry about what is behind you.
I'm extremely nervous to go into any type of mountains. Isn't it true that there is a way to break also? I was told when braking to brake and let up a little and brake again so it's not a constant pressure.
The brake linings will not withstand constant contact on downhill running at "normal" speeds.
There is too much energy to convert into heat.
The driver is a heat manager on downhill sections.
The coach has to be controlled by a combination of slower speed, choice of lower gears, and occasional use of the brakes.
As a option, an engine brake/Jacobs engine brake/exhaust brake/transmission retarder is a feature which increases the driveline's ability to make some slowing force.
Quote from: richard5933 on June 28, 2018, 08:50:29 AM
eagle19952 - What's the upper speed you can maintain with your 740 in 2nd gear? In our 4108 with the 4-speed, 2nd maxes out at about 30 mph.
Depends. Uphill ? I've seen 22mph. this would be the west side of Yosemite (Tioga Pass).
My post refers to down hill.
With the Allison and no Jakes. One is best to try to hold the same, 20 mph.
My point, if one does not know the lay of the land...
Like warrior said, there is no worse experience than your brakes getting worse than they were 1/4 mile ago...
Personal experience with the MC8 8v71n/HT340, 32k pounds at the scales, got down the west slope of the Sierras, some sections at 6%, with Jakes on with no issues. Occasional braking at the end of the steep sections leading into curving sections. Transmission gears were also used with the Jakes to maintain a comfortable brake off speed.
When using engine to assist holding coach back,, watch rpm's that they don't exceed governed speed.
Quote from: chessie4905 on June 30, 2018, 03:39:49 AM
When using engine to assist holding coach back,, watch rpm's that they don't exceed governed speed.
No tach. Best I can do is keep an eye on the speedometer. I'm good to about 50 in 3rd.
One should learn to descend without the Jakes they can go away in a hurry on a older 2 stroke engine.i am not a huge fan of Jakes on the old Detroit the more you use the Jake on a 2 stroke the more oil it uses.I have always had Jakes I just never used them that much and we traveled all over the west
Go as slow as you need to in order to feel comfortable and safe. What's behind you doesn't matter. I see way too many trucks on semi-controlled downhill runaways, one tight corner or stopped vehicle away from a disaster.
The first thing I had done to my 8V-71 was installing Jakes. I know how well they work from my experience with my 8V-92TA. When pulling my car I weigh 34,750lbs. Going down the north bound I-5 Grapevine-5% grade of 5 miles, I can maintain 50mph without touching brakes. When up in the mountains, I just pull the shifter down to 1st and get torque converter lockup down to 20mph. In 1st the Jakes are really powerful. In my opinion-if you have drum brakes and travel west of I-25, Jakes are needed. Good Luck, TomC
Quote from: TomC on June 30, 2018, 03:54:49 PM
The first thing I had done to my 8V-71 was installing Jakes. I know how well they work from my experience with my 8V-92TA. When pulling my car I weigh 34,750lbs. Going down the north bound I-5 Grapevine-5% grade of 5 miles, I can maintain 50mph without touching brakes. When up in the mountains, I just pull the shifter down to 1st and get torque converter lockup down to 20mph. In 1st the Jakes are really powerful. In my opinion-if you have drum brakes and travel west of I-25, Jakes are needed. Good Luck, TomC
most don't have 1st gear lock down...
I drove many miles in California and Oregon and used the stabbing method to keep the speed down in the mountains. Now I have Jakes and really like them, like Tom says with Jakes you don't need to brake to slow down. However, I had to follow the trucker's advice and set the Jake clearance a lot tighter than the books give you in order for them to work good.
The Jakes work quite well on my 6V92TA. They feel about the same as the ones on a loaded semi. I did set them tight. Can't remember off the top of my head how tight, I'd have to look it up. I drive with them on most of the time. It is nice to have as an anchor if you take your foot off the pedal.
On the new Prevost and MCI cars now, the engine brakes (they are not Jakes, they are proprietary systems to Volvo and Cummins), don't come on instantly when you take your foot off the pedal, it takes a few seconds before they activate. So I only use them to go down a hill.
As you get to know your bus, you will know which gear to use to go down what grade. Start slow, and go up from there.
JC
The Jakes work quite well on my 6V92TA. They feel about the same as the ones on a loaded semi. I did set them tight. Can't remember off the top of my head how tight, I'd have to look it up. I drive with them on most of the time. It is nice to have as an anchor if you take your foot off the pedal.
On the new Prevost and MCI cars now, the engine brakes (they are not Jakes, they are proprietary systems to Volvo and Cummins), don't come on instantly when you take your foot off the pedal, it takes a few seconds before they activate. So I only use them to go down a hill.
As you get to know your bus, you will know which gear to use to go down what grade. Start slow, and go up from there.
JC
Sorry, double post. This new forum platform tells me someone else posted while I was typing, so I hit post. But the someone else was me...
JC
0.055 is about as close as you can set Jakes on a 92 or 71 series me I don't chance it I stick with the 0.059 Jake gauge.I replaced 2 heads on 8v92 where the owner decided if 0.055 was good 0.045 was better.Me and my buddy Don don't see eye to eye on that one he sets those at 0.055,one really needs to know what cam the engine has before he starts playing around with adjustments on Jakes or it will bite you in the @$#
Mine are set around .035. The only way you can hurt the engine with the Jakes tight is if you overspeed the engine rpms going down a mountain. That would bend the valves by them hitting the pistons. I've had a few customers do that who did not even have Jakes, and one who downshifted with the Jakes on.
Nope beginning in 1985 when DD started the emission game they were changing cam lifts like people change socks .Set your Jake's on 0.035 on a DDEC engine and see what happens the 1st time you turn it on.0.059 was the safe number for all the cams and I am sure they didn't come up with that number for no reason so it is 0.059 for me
I'm talking pre-DDEC, and you're right.
But, what a difference between .059 and .035! Jakes are nearly worthless at .059-- you hear a little puff-puff and keep rolling. I go down the Tehachapi mountains on low Jakes (1 bank) and have to turn the Jakes off so I don't roll to a stop. Without Jakes it was frequent stab braking.
Geoff
The setting on the 71 series was 0.065 the 0.059 was a improvement with the 71/92 heads
I looked at my records. .059" is what I set mine at, on Don Fairchild's recommendation. Works good for me.
JC
Quote from: lostagain on July 01, 2018, 11:29:31 AM
I looked at my records. .059" is what I set mine at, on Don Fairchild's recommendation. Works good for me.
JC
Don will go to 0.055 on some engines ,but I don't have problems with Jake's set 0.059 working like they should
We are debating .059 v. .035. = .014. The average thickness of a man's fingernail is .384. When I see damage from valves hitting pistons, it is closer to 1/8 to 1/4 of an inch bend. It's not from too tight of Jakes clearance from normal use. Get a feeler gauge and dig out a .014 blade. I'm not inclined to go measure the cam lobes staying open with Jakes, I just know what works and what fails. I have mine at ,035 and the Jakes work better with no floating valves.
Geoff
Quote from: Geoff on July 01, 2018, 03:43:03 PM
We are debating .059 v. .035. = .014. The average thickness of a man's fingernail is .384mm. When I see damage from valves hitting pistons, it is closer to 1/8 to 1/4 of an inch bend. It's not from too tight of Jakes clearance from normal use. Get a feeler gauge and dig out a .014 blade. I'm not inclined to go measure the cam lobes staying open with Jakes, I just know what works and what fails. I have mine at ,035 and the Jakes work better with no floating valves.
Geoff
LOL I see you changed the .384 to mm I thought that person would have some very thick finger nails over 3/8th inch thick nails 8,really Geoff I don't have any problems with Jakes working at the 0.059 adjustment a Jake gauge is all I use
I don't care either, I had a hot weather bad day yesterday.
Quote from: Geoff on July 02, 2018, 09:32:50 AM
I don't care either, I had a hot weather bad day yesterday.
How's your back doing Geoff?
My back is fine after the operation to dig out all the chipped vertebrae that was pressing on my spine. It took almost a year for them to operate.
Thanks for asking
Geoff
Good remember you were going in. Glad it came out well or at least probably etter than when you went in.