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Old 03-27-2020, 03:16 PM   #81
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The key to downshifting is to do so before you need to. On the flat or upgrade just before you know there's a down grade. then you won't experience that slipping.
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Old 03-27-2020, 04:17 PM   #82
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The key to downshifting is to do so before you need to. On the flat or upgrade just before you know there's a down grade. then you won't experience that slipping.
If you downshift early and hit a downslope, once the engine torque is more than what the friction that a tire can hold...wheel slippage on one or more tires occurs. You want the ABS to control the slippage which will not happen if you are in a low gear.
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Old 03-27-2020, 05:43 PM   #83
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Yes to all those who clarified the downshifting. DO NOT DOWNSHIFT IF YOU ARE ALREADY GOING TOO FAST. I use it to maintain the speed I want without having to be on the brakes all the time. I still use the brakes to slow down from the speed I'm looking to hold.
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Old 03-28-2020, 01:22 AM   #84
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This is what I meant by downshifting before you need to, not while you're speeding up. Lower gears help keep you from speeding up, and when you need to, then apply the brakes gradually, to maintain you're lower speed. And as was said by others, occasional touches on the manual trailer brakes will keep the trailer behind you and help maintain your lower speed. I travel the Sierra's a lot and was on I70 last summer pulling my Forest River Surveyor. Used 2nd gear a lot with occasional breaking to stay below 40-45. If I were on there in the snow, I would be in 1st gear and not exceeding 20 mph, and of course have chains on the rear wheels of the TT. Actually, I hope I wouldn't find myself traveling that area in the snow or any mountain roads pulling a TT in the snow.
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Old 03-28-2020, 01:41 AM   #85
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This is what I meant by downshifting before you need to, not while you're speeding up. Lower gears help keep you from speeding up, and when you need to, then apply the brakes gradually, to maintain you're lower speed. And as was said by others, occasional touches on the manual trailer brakes will keep the trailer behind you and help maintain your lower speed. I travel the Sierra's a lot and was on I70 last summer pulling my Forest River Surveyor. Used 2nd gear a lot with occasional breaking to stay below 40-45. If I were on there in the snow, I would be in 1st gear and not exceeding 20 mph, and of course have chains on the rear wheels of the TT. Actually, I hope I wouldn't find myself traveling that area in the snow or any mountain roads pulling a TT in the snow.
Read post #75 again. He said it perfectly.


The brakes need to be slowing you down when in ice or snow. Not the engine.


I have a house in Tahoe above you from Pollock Pines. Been driving the Sierra for years in snow.



I also worked for GM on adaptive cruise control and how it used ABS. Did a lot of driver training at the GM proving grounds which showed the importance of keeping the wheels moving at all times.
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Old 03-28-2020, 08:55 AM   #86
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I hope I can explain this in a way that makes sense...

The first thing they teach you about winter driving when getting your CDL is that you disable your engine brake on slick surfaces because you don't want to use compression braking/engine compression to slow down. That puts you in a slide that is very difficult to recover from.

Using high RPM compression braking you are using your drivetrain to provide rolling resistance to the drive tires. If this resistance from the drivetrain overpowers the friction with the road surface the drive tires change speed and slip. Applying (or releasing or pumping) the manual brakes to a slipping tire won't do you much good after it has already lost traction, you need to increase the rolling speed of the tire to match the road surface to regain traction. The problem is, if you are already up there in your RPM's (because you were using high RPM compression to hold you back in the first place) you now have to add throttle to increase the rolling speed of the slipping tires and remove that rolling resistance which is preventing your drive tires from grabbing traction. This is hard to manage when you are panicking. And even if you do pull it off and keep control you are now traveling faster than you wanted to be, compounding the problem.

Using a higher gear/lower RPM and gentle braking to maintain speed is much safer. The lower RPM's decreases the drivetrain resistance so you are less likely to have drive tires slipping from that resistance. And using manual braking to slow gives you the benefits of your ABS system releasing the braking forces from any slipping wheels allowing them to roll freely to regain traction, which they can't do if engine braking is holding them back. If you don't have ABS (or it doesn't work or whatever) just letting off the brakes briefly will let the drive tires roll freely and regain traction, allowing you to then apply gentle braking pressure again. Doing this you will have brief moments where the vehicle will pick up speed from the gravity forces pulling it down the hill, but you will quickly be right back on the brakes.

This is easier to get a feel for in a semi because we don't tend to spin out in a circle and into the ditch in the blink of an eye the way 4-wheelers do. Running doubles back and forth over the Utah mountain passes all winter long I've had the pleasure (or displeasure ) of learning just what it feels like to have your drive tires sliding from too much engine braking.

In a nutshell, you want low RPM's so that your drive tires are rolling freely and you are using the brakes as needed.


Excellent explanation. It's the same reason you let off the brakes if the car starts to skid so as to keep the tires rolling. The same principle of ABS.

Perhaps the term "downshifting" shouldn't be used. What I meant was that I use a lower gear to keep from going too fast, not to slow down after I'm already going too fast.
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Old 03-28-2020, 11:34 AM   #87
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Excellent explanation. It's the same reason you let off the brakes if the car starts to skid so as to keep the tires rolling. The same principle of ABS.

Perhaps the term "downshifting" shouldn't be used. What I meant was that I use a lower gear to keep from going too fast, not to slow down after I'm already going too fast.
Reread his explanation. "Higher gear/lower RPM"
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Old 03-28-2020, 12:57 PM   #88
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It's still hard to fathom. On the 3 mile down grade to my home, if I use a higher gear, I'm riding the brakes almost all the time to stay under 40 mph. If I use lower gears, 2nd or 3rd, I rarely have to use the brake as the engine keeps me under 40. Speed limit is 40.
This has always worked on dry pavement, and seems to always work on snow conditions.
Ford 2015 3.5 Eco-boost. 18 years now, and apparently I've been doing it wrong, yet I've never had a slipping issue by keeping my speed down using lower gears. I know not to apply brakes on a curve, but to apply gently before the curve. ???
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Old 03-28-2020, 01:02 PM   #89
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It's still hard to fathom. On the 3 mile down grade to my home, if I use a higher gear, I'm riding the brakes almost all the time to stay under 40 mph. If I use lower gears, 2nd or 3rd, I rarely have to use the brake as the engine keeps me under 40. Speed limit is 40.
This has always worked on dry pavement, and seems to always work on snow conditions.
Ford 2015 3.5 Eco-boost. 18 years now, and apparently I've been doing it wrong, yet I've never had a slipping issue by keeping my speed down using lower gears. I know not to apply brakes on a curve, but to apply gently before the curve. ???
We are talking snow conditions. You won't be going 40MPH in snow conditions where you are worried about ice and your wheels slipping. If there is R1 chain control or higher going on, the speed limit is 25MPH anyway. The difference in energy between 25MPH and 40MPH is a factor of 2.5.


The elevation your town is at is less than 4000 feet. Likely, very rare you even have an issue. Until I started travelling 395, I use to go up 50. I can count only once or twice in 30 years there was even snow on 50 at Pollock pines.
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Old 03-28-2020, 01:30 PM   #90
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Yes, I know to keep it under 25, usually under 20 coming down the last 3 miles of downgrade. I use 2nd gear, or otherwise, like I said, constantly using the brake if using anything higher than 3rd gear. I drop to lower gears before reaching the crest of the road. Never while descending except on dry pavement. 35" of snow in March. Had to take my wife to work in Placerville twice this year as snow was too deep for her Subaru Legacy. 14" on our road.
3 times last year in February when we got 42" of snow in one month. Once we get to highway 50, it's usually okay. Just keep it below 25 and the grade is not that steep on 50 as it is on Sly Park.
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Old 03-28-2020, 04:17 PM   #91
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I live in the Buffalo, NY area. Some say we are the snow capital of the world even though we aren't even number one in NYS, Syracuse is!

I admit that I have never pulled a TT with a pickup, though at one time I did pull a 22 ft. boat around the Northeast for some time. And, I can't even imagine what the OP went through with his harrowing tale of a scant 15 mile half hour drive to his campground. Well done OP for maintaining your cool under enormous pressure!

That being said, I would have to agree with pwrriver and his position on shifting to "a lower gear" before the steep decline. I practice this daily during the winter months driving around WNY, albeit in an all-wheel-drive SUV vs. PU and TT. I will use lower gearing to slow down coming to stop signs, hills, take-off from a stop so you do not have excessive wheel spin, etc. To me, if you leave your vehicle in high gear (OD?) the vehicle will want to travel at a higher rate of speed because of the gearing. Manually downshifting BEFORE the downhill will restrict the speed of the wheels turning by the transmission first, then the engine which will spin at a higher rpm while the wheels, controlled through the transmission turn at a slower rate, hence a slower downhill speed. This would, of course, would work in conjunction with modest steady braking keeping everything in order. Now again, not ever towing a TT in these extreme circumstances may present an entirely different challenge that I'm not akin too, but this is what I would do. I am a big believer in the old truckers' axiom of using the gear to go down the hill with the same gear you went up. My furthest trip out West where yes the mountains are high was to Mt. Rushmore, SD at 6100 ft., Deadwood at 6600 ft. and Devils Tower, WY at 6800 ft. with my gas Georgetown. We encountered numerous 9% grades that I used the Ford tranny to keep my rig and tow dolly and car in check coming down. Sure, middle of July isn't the same as a snowstorm pulling a TT.

An ironic part of this thread is Covid-19 emergency depending, my DW and I have a trip planned to Napa in September this year. We have a tentative plan to spend upward to two weeks along I70 traveling though Colorado!
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Old 03-28-2020, 04:27 PM   #92
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Enjoy your trip, Sherman and Barb. September should be a great time. Safe travels.
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Old 03-28-2020, 07:29 PM   #93
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Dear babcock
Your answer confused me with what I've always learned so I researched it in several places along with googling it on the internet. All sources agreed with the following two sources.
California 2020 Drivers Handbook. Pages 93 and 94. Driving on ice and packed snow. Page 24, bullet number 5. "Shift to low gear before going down a steep hill".
2015 Ford F-150 4 wheel drive supplement Driving in deep snow on hills. Page 11, paragraph 2 "Use a lower gear before you begin your descent down the hill to avoid excessive breaking.
So I'll stick with my method that I've used for the last 18 years driving in snow and shift to a lower gear that will help maintain my speed below 20-25 mph when descending a hill. It's worked for me and if that question comes up on my test next year, I'll know the correct answer.
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Old 03-28-2020, 07:40 PM   #94
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"Use a lower gear before you begin your descent down the hill to avoid excessive breaking.
There is a difference if you also have a heavy trailer pushing on you that does not have engine braking slowing it down. That is when the higher gearing and letting ABS help you kicks in.
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Old 03-28-2020, 08:09 PM   #95
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Well, there is one thing I have learned from all this conversation. I will be buying a set of cables for my trailer. Will likely never need them but better to have and not need than to need and not have. They will go in the storage compartment and hopefully never have to come out. We don't take the TT out in the winter time unless it's to Palm Springs or Arizona desert, but just in case we're in Colorado in the summer and get hit by a freak snow storm, we'll be prepared.
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Old 03-28-2020, 08:13 PM   #96
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Dear babcock
Your answer confused me with what I've always learned so I researched it in several places along with googling it on the internet. All sources agreed with the following two sources.
California 2020 Drivers Handbook. Pages 93 and 94. Driving on ice and packed snow. Page 24, bullet number 5. "Shift to low gear before going down a steep hill".
2015 Ford F-150 4 wheel drive supplement Driving in deep snow on hills. Page 11, paragraph 2 "Use a lower gear before you begin your descent down the hill to avoid excessive breaking.
So I'll stick with my method that I've used for the last 18 years driving in snow and shift to a lower gear that will help maintain my speed below 20-25 mph when descending a hill. It's worked for me and if that question comes up on my test next year, I'll know the correct answer.
When you are in your low gear and your tires start sliding down the icy hill because the engine compression is causing it and you basically threw your ABS system function away, you will know the correct answer.


read post #75 again.
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Old 03-28-2020, 08:25 PM   #97
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your first paragraph in starting all this conversation referred to "The first thing they teach you when driving in winter snow when getting your CDL is contrary to what they have in the CDL Handbook pages 93 and 94, driving in ice and snow. What works for you is fine. What has worked for me for 18 years driving in snow is fine with me and complies with my Ford manual and the CDL handbook. My wife also had a a WINTER DRIVING safety class from an El Dorado COUNTY safety seminar, and he confirms what I have always taught her. Downshift to lower gear before cresting the hill. Just sayin.
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Old 03-28-2020, 08:34 PM   #98
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your first paragraph in starting all this conversation referred to "The first thing they teach you when driving in winter snow when getting your CDL is contrary to what they have in the CDL Handbook pages 93 and 94, driving in ice and snow. What works for you is fine. What has worked for me for 18 years driving in snow is fine with me and complies with my Ford manual and the CDL handbook. My wife also had a a WINTER DRIVING safety class from an El Dorado COUNTY safety seminar, and he confirms what I have always taught her. Downshift to lower gear before cresting the hill. Just sayin.
When I was a design engineer at GM and driving modified cars, we were given extensive drivers training at the proving grounds in Arizona. They put us on "slick" tracks that mimicked driving on ice. First thing they had us do is down shift to show us how the ABS was ineffective. They drilled into our brain to keep the wheels moving. They had us drive the slick tracks with and without the ABS turned on.


Go to the commercial driving handbooks. They say to turn off the engine braking devices on snow and ice!


https://www.dmv.ca.gov/web/eng_pdf/comlhdbk.pdf
page 2-11
Quote:
Caution: When your drive wheels have poor traction, the retarder may cause them to skid. Therefore, you should turn the retarder off whenever the road is wet, icy, or snow covered.
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Old 03-28-2020, 08:45 PM   #99
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When I was a design engineer at GM and driving modified cars, we were given extensive drivers training at the proving grounds in Arizona. They put us on "slick" tracks that mimicked driving on ice. First thing they had us do is down shift to show us how the ABS was ineffective. They drilled into our brain to keep the wheels moving. They had us drive the slick tracks with and without the ABS turned on.


Go to the commercial driving handbooks. They say to turn off the engine braking devices on snow and ice!
Same goes for cruise control on automobiles. Once the drive wheels hit the ice the throttle can get a mind of it's own. From there it usually means a bad ending.

If one has an EV with manual Regenerative Braking or can select a more aggressive regenerative setting on what would normally be the shift lever (like on my Volt), avoid manual regen braking and leave the selector in standard "Drive".
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Old 03-29-2020, 08:04 AM   #100
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I’ve really enjoyed reading this thread and have learned a lot from it.

Thank you, all.

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