Hi Everyone! Very new and trying to not bother everyone with too many questions but I have one that involves safety and I haven't been able to find an answer despite searching at length, so here goes.
We are the current caretakers of 1244 (2008 - C15/ZF12) and tow a Jeep Gladiator (BlueOx/Air Force). We will be taking our first trip that involves mountain passes in the near future and I would like to better understand the interaction between the cruise control, the transmission, and the brakes based on our setup. Specifically, if I set the cruise at 60 and have the jake brakes engaged (high setting), on descent should I expect the cruise to cause the transmission to downshift to keep me near the set speed or do I need to manually downshift to match the retardation of the jake to the slope of the descent?
Thanks in advance for any answers.
Best regards,
db
Your setup may be different from mine.
In my situation, the cruise will not hold you to a set speed on a lengthy downgrade. What happens is the throttle closes activating the jakes when the set speed is exceeded, but if the slope is steep enough it will NOT downshift the transmission.
I do not run with the cruise in the mountains. I select the downhill gears according the grade, curves, and speed I want to run. Keeping in mind it is far easier to speed up going downhill in these monsters than it is to slow down. I find that 5 to 10 mph slower than posted for the cars keeps my co pilot from levitating.
Your coach may respond differently than mine.
Thanks, that is extremely helpful. Based on my equipment/load (I haven't visited a scale yet so I can't tell you my exact weight. especially with our toad), what gear do you suggest I select when cresting into a 5-6% grade (thinking I-75 Northbound in Tennessee)?
Typical wisdom is to go downhill in the same gear you went uphill in. If you downshift to 2nd or 3rd going up then start going down in that gear. Be ready to use jake and service brakes to drop your speed when needed.
I had a different experience in my 2001 Newell. When going downhill, the cruise control downshifted as required, which worked perfectly unless the grade was excessive, they I applied temporary breaking to assist the cruise control.
I should also point out that climbing a hill, the cruise control was smarter than me since it would downshift as appropriate.
Words of wisdom from my father who was a trucker and had RVs for 40+ years. This was prior to our reunion in Silverton CO.
"If you get in a crash you are the first one on the scene!"
Thinking of this and our seating positions in our RVs I got the message.
In our Newell and our previous toyhauler & RAM Dualie, my experience in big grades downhill is I-77 going from VA into NC. I don't use my cruise control in the mountains. Colorado was so long ago I forget if I had any white knuckle rides.
Here is how I approach downgrades. I don't use my cruise control in the mountains.
I slow down before the summit and get into the gear I want to descend the hill in. This speed will be below the posted speed. I take my cue from the trucker's speeds. I'm not afraid of going slower than I want. I keep an eye on my RPMs as well as speed. Use the brakes when speed or RPMs dictate and then keep my foot off of them to allow time to cool between uses. Don't ride the brakes.
In the 1970's dad always taught us that if you lose your brakes don't try to ride it out to the bottom. Put it right into the side of the hill because you aren't going to be going any slower than that moment. Today I'll take into account if there is a runaway truck ramp nearby.
Thank you for the replies. I am hoping that my experience mirrors Chester's with the cruise set point being the suggested 10mph or more below the limit (my wife doesn't like levitating, either) but, as they say, hope is not much of a plan.
If anyone has experience with my setup (C-15/ZF12) or other helpful tips, I am all ears. I should mention that 1244 had the Vorad but it is currently disabled (bad CPU) - but I have a NOS CPU to install (miraculously found the same P/N) so, again hopefully, that will not be an issue as I understand the Vorad interacts with the cruise.
Hard to say what gear because you have a lot more to choose from than most of us. But, you will know what gear when you get there. That’s not a smarty pants answer, but rather means as you start down the grade and let off the fuel, the jakes will activate. If you find that you start to pick up speed and approach your comfort limit, then downshift one gear. Rinse and repeat, with continued downshifting until you get the speed you desire.
The lowest I ever downshifted into was 2nd gear. That was descending into Ouray on Hwy 550. I was going about 10 mph.
(04-24-2023, 10:24 AM)Richard Wrote: [ -> ]The lowest I ever downshifted into was 2nd gear. That was descending into Ouray on Hwy 550. I was going about 10 mph.
Richard,
This answers a question I've kept to myself since I bought our Newell. I know we will be on The Million Mile Highway in the next couple of years.
I would rather up shift going down hill than need to downshift and can't.
I go down slow at least 5 below posted. When I see the tipping over truck sign I pay close attention.
I don't mind holding up traffic, my concern is all about not needing to do laundry at the bottom of the hill.
Take the first few slopes slowly and cautiously. A close eye on the RPM's while on flat level ground will tell you a lot about when the transmission wants to shift. Knowing that I try to keep the RPM's below that value on the downgrades. That allows me a quick downshift if I need it.
I too have been in second coming into Coeur d'Alene. Heavy traffic and it didn't feel right to pop into the left lane to pass. I figured the people in front had enough stress without me adding to it on their left.
I am never in a hurry driving the coach. The beverages will stay cool in the ice box.