Well I thought I'd outfoxed the highway system, coming from Roanoke Rapids, NC to Flat Rock, NC saw a route (hwy. 74, beautiful road!) that looked as if I wouldn't have to do that 7% grade coming into town on I 26....ha ha....imagine my utter horror/shock/dismay when I discovered (after only a few casual pointers on mountain driving here & there from various folks) the grade was still ahead of me!!!! :o
So, I put on my 'big girl pants' (should have been Depends) & off I blindly chug (first time towing too!) up the mountain, 15-20 mph, freaking out, watching the gears shift on their own, sighing & shuddering all the way up....& watching the temp gauge climb from it's normal spot to about 5+ degrees higher.....that did it.....I finally pulled over (thank goodness there was a passing lane & a shoulder)....waited a few minutes then decided I just had to call in the 'A' team...(or in this case the 'A-B' team, as in Gary B)....thank goodness again for a cell signal at the top of the hill, & then double thanks that our wonderful FT guru Gary Bouland actually answered on a Sunday afternoon!!!! O:)
So, damsel in distress (this ain't the 1st time this wonderful feller's bailed me out) whining aside, Gary B proceeds to give me a crash course in gauges & gears...talked me all the way the mountain....RPM's, temps, gears, retarder, all the good stuff....folks, if it hadn't been for this amazing man, I'd still be sittin' on top of that grade in tears! So, a huge thanks (once again!!!) to one of our most beloved FoFum members!
At least now I think I have a little more confidence now to get up & down big grades again, though am not wild about the notion.
Gary, & Miz Jane, his dear lovely wife, I love you guys! (Just when you think all your kids were already raised, ha ha.....)
Glad you made it safely and you have some good sperience now. Gary is a great guy. Glad he was able to help. He has helped me as well. Have a safe trip Aunt Dani
Miz Dani, good morning! I wonder if a reminder turtorial by you and Gary could be appropriate here now? Summer comes with its mountainous attractions. There have been threads related to this and magazine articles, such advice I carry in a three-ring (yes Roger, I need to scan those!) but a concise reminder would be nice...what did your saving guru say to do Dani?
Thanks!
Mike
I may wait & let Gary B add to the "reminders" but basically I was to keep her in 3rd gear all the way down, watch the RPM's so they never got too high (like maybe in the mid to high 20's! so I kept them around 15-17) & the temp amazingly stayed down at normal!!! (about 181). Never touched the brakes, retarder was magnificent, as always!!!! Kept her chuggin' downhill at about 25mph & the rest is history....this in my 8th hour on the road!
However, steep grades will have to happen again one of these days so I guess it wouldn't hurt to have anybody who wishes to chime in & offer more but Gary B is pretty much the expert in my book, along with another famous Gary that happened to be partying in Nashville that day!)
I am afraid that a tutorial here might not be of much use. I dont want to embarrass Dani but my conversation with here was specific to her situation at the moment. I gave here as little basic info as possible to get her safely down the grade without overloading her with stuff that would just confuse her in the situation she was in.
That lady is gutsy, she took the ladies driving course and all she lacks is experience and there is only one way to get that. I would tell her she needs a boyfriend to teach her truck driving but then she would probably never talk to me again. :) Or, she might says words to me that were not nice. :)
Hang in there Dani, one day you will look back on this little adventure and laugh like hell.
Gary B
I'll start the tutorial. When climbing, don't rely on the tranny for gear selection. Select your gear on the keypad to keep rpm at max torque-usually 1500. If you can't accelerate in the gear you're in-downshift.
Going downhill, use the lowest gear you used climbing. Use the retarder before the brakes to keep rpm's below max-usually 2700. If the retarder isn't enough, use the brakes firmly to reduce rpm below max-don't ride the brakes. Apply firm pressure, then get off them.
Congratulations on making a good decision to ask for help. A lot of others, mostly men, have done much worse. Probably the reason women have fewer accidents. I remember driving 74 in a car when I 26 was under construction and thinking how much better it would be after I 26 was finished.
....yes, my dear adopted nephew, & it's partly your fault ;) since you're the one who found me this beautiful FT critter! :))
Anyway, Gary B is too modest, he pretty much guided me down the whole way & since I was freaking out, kept it simple & as always, in his calm, reassuring voice.....so it's nice that I lived to tell about it....thanks guys for all the tips, & yes Brett, I should have made that call before I even started up the mountain but I thought I knew what I was doing....next time I won't wait so long for help.....
Brett, I seem to recall something about retarder/transmission temperature, to not exceed...what? I can get to warming from the usual 180 degrees up to 205, even 210 without very prolonged effort, and that in grades that are not steep for a long time or they are gradual for quite a distance. Is the max 230 to allow, seems I read that in some thread...?
So, protocol is to
a. downshift to a gear that keeps rpm below.....x (varies by engine model, as ISM, ISL, ISC?)
b. use retarder to slow the coach but keep transmission temp below....y
c. use brakes to help adjust the rpm and temp, but caution on using the brake too much, how to know too much?
d. pull over and let cool if temps (engine or tranny, or both?) too high or rpm climbing too much in the lowest gear you can use?
I do not have an EGT gauge. Is that a vital omission in this situation(s)?
mike
Mike,
Basically the service brakes (brake pedal) are used on a descent ONLY to slow you down enough that you can select the next lower gear. Correct speed of descent on any grade is with speed in EQUILIBRIUM. That is your selection of gear and retarder setting keep your speed from going up or down. If you start slowing down, ease up on the retarder. If you start speeding up and are already at a high engine RPM or high retarder setting, use the service brakes enough to drop to the next lower gear.
Unless you have hopped up the engine, and EGT is just a gauge "of interest". The engine manufacturer's settings will not allow the engine to harm itself in standard form.
Since the retarder turns momentum into HEAT in the transmission, your cooling package (engine driven water pump and radiator) are used to dissipate the heat. So, higher engine RPM turns the water pump faster and will dissipate more heat. There is no magic number for transmission fluid, the hotter it is, the shorter its life. Clearly, if the transmission temperature is rising, dropping a gear/slowing down and backing off retarder setting will both generate less heat (requires less braking HP at, say 30 MPH than at 40 MPH AND the higher engine RPM's dissipate the heat better.
And, yes, when climbing a grade, if engine temperature starts rising (200 degrees F) is my "I need to start being proactive", slow down and gear down. It takes less HP to climb a grade at 30 MPH than at 40 MPH. Generating less HP produces less heat in the engine. Keeping engine RPM in the middle or slightly above the middle of between peak torque and peak HP at less than WOT (Wide Open Throttle) should work just fine unless it is over 100 degrees F and a long steep grade.
Which brings me to the 4 numbers everyone should know for their engine. Call your engine manufacturer with your engine serial number for them:
Peak torque RPM (do not operate your engine below this RPM except at very light throttle positions).
Peak HP RPM (no reason to go above it, as HP drops off and MPG's drop WAY off)
Governed RPM (the fastest you can turn the motor under load)
Maximum permissible RPM (the fastest you can turn the motor when not fueling-- like when going DOWN a grade).
Thanks Brett....think you tried to tell this before in a magazine but i could surely use this to good end for the climb and return down this summer, get my data/info organized.
Thanks
Mike
Other comments;
Put 4 way flashers on if going up or down in slow motion.
Never worry about the guy behind you going up.
Keep your eye on the rear view mirror coming down and DO worry about the guy behind you if on a one travel lane road and he's coming fast, don't worry so much after a few vehicles bunch up behind, they will give you a cushion if someone comes barreling down out of control.
Once I had to come down a very steep grade with a hairpin turn with no Jake brake ,subsequent investigation revealed a bad ground. I just put it in first gear with 4 way flashers on and came down at the speed the coach equalized at. It was pretty slow and sometimes I had to give it some throttle but I was not going to upshift for anybody. Many cars backed up behind me and we all made it to the bottom safely.
2100 rpm absolute red line on my CAT 3176B with Jake brake on. I have a small slice of red tape at that mark on the tach.
It depends on where you measure the transmission temp but if it is the sump then you should not exceed 250 degrees. A five degree jump in engine temps is not much. I run at 180 and it will jump up to 190 on a steep long grade. I know that the longest steepest grade I have driven in the hot summer was I 70 and that got my temperatures up to 205 and I had already taken my foot out. I think the issue is the bigger coach at 42 foot and the two slides and a Grand Cherokee that has the same cooling package as my 36 foot none slide 320. That makes my coach a bit easier to heat up but it comes down quickly. I think with more experience you will have no issues climbing hills. They get to be pretty nice change of pace and you actually get to drive going up and down and that is fun.
The most important step is taking it seriously and recognizing that there is something to take seriously. Everything else is just details. Oh and I have been honked at going north of 30mph (irresponsibly fast) down a steep grade. People don't get it so you have to roll with it.
Brett--What a great, concise summary. (Thanks for helping the Damsel, too.) We are getting ready for mountains and know the Transmission Prayer from our other rigs. Keep the information coming and we will take notes. Thanks! Paul
Our 8.3 was turned up with the Banks kit so EGT is a real issue for us. I found a long pull in the Rockies last summer became manageable when I got into 3rd gear. The more RPM's the better your motor can belch heat through the exhaust and hydraulic cooling fans will spin more effectively. Feathering the throttle in 3rd is infinitely easier than lugging around 1600 RPM's in 4th .
Complete swap to Transynd equivalent tranny fluid and new filters is cheap insurance for both pulling and braking wear.
Good luck!
What about those of us with no joystick controller? We HAVE to apply service brake in order to activate retarder.
Don't let your speed build up to much before applying brakes. As someone earlier mentioned, apply them hard enough to drop your speed back down quickly. Then get off them. Do NOT pump the brakes. You won't reach the equilibrium thing that Bret mentions, so it's speed up, slow down, repeat. The longer time in between, the better.
Here are the numbers for our C8.3 mechanical engine (Determined by engine serial number input @ Cummins QuickServe Online (https://quickserve.cummins.com/info/index.html)):
ADVERTISED HP: 300 @ 2200 RPM
GOVERNED HP: 285 @ 2400 RPM
TORQUE PEAK (lb-ft): 820 @ 1300 RPM
HIGH IDLE: 2760 RPM
GOVERNOR BREAK RPM: 2450
Should I assume (for me, always dangerous) that the HIGH IDLE number is equal to "Maximum Permissible RPM" ?
Guess that's why 1300RPMs seems like the sweet spot on our coach.
Roland
In my experience every single Rv owner panics if the engine temp gauge moves off the peg.
It's SUPPOSED to move. No Rv has that much reserve radiator capacity to not have the needle move.
Early grand villa u280 250 hp cat 3208's had the same radiators as the u300's.
Over cooled the engines. Foretravel ended up blocking part of the radiators as the motors ran too cool.
I run mine regularly to 210-220 range up long grades at temp.
Radiator Fan does not get to full speed to 210 on a electrically controlled m11 cummins cooling fan switch in a truck.
Versus pull over at 185? Miz Dani keep your foot in it.
Done countless delivery drives up baker grade in California at 110 ambient where the coach gets to well past boiling point of water to demonstrate no coolant loss and no damage ever.
While I am sure it is quite fine and that cummins builds some safety margins in, I believe the magic number to not exceed is 210 per the manual. For me that means I run until it hits 200 and then I start handling to try to keep it there. I must admit I was frightened when I first saw it rising after driving cars all these years, especially BMW's with idiot gauges that stay precisely in the middle as long as the temp is in the correct actual range. Then there is the whole thing with some of these coaches that causes the coolatn temp to read 5-10 higher when the headlights are on which also threw me.
Kind of makes me wish for a list of those build numbers..... :-X
for the 8.3 cummins, you want to pull a large hill around 1900-2100. Peak torque is irrelevant for going up a large grade. You want to be around peak HP. In numbers given above, 2200rpm with pedal to the floor is going to give you the fastest speed up the hill. You want to run the engine where it is designed to run. It's better to shift down a gear and run the engine at 2200-2300rpm with less throttle than it is to lug it at 1500rpm with pedal to the floor (these numbers are for the 8.3 cummins)
That's the reason the cooling system is pressurized. To raise the boiling temp of the coolant........
That's why (at least in my opinion) the cost to upgrade to the joystick is well worth it. Once you've experienced the pleasure (and extended brake life) of regularly activating the retarder with the joystick with minimal use of the brakes, I don't think you'd ever want to go back to not having one.
The non joy stick Allisons are not a problem. The first application of the retarder takes place well before the brakes are fully engaged and the harder you brake the more retard application you get. I never had a problem with the 95 U280 that I had, just a different mindset with no joy stick.
Gary B
Correct. A well calibrated foot is a three position joystick, giving you two, four, or six clicks of joystick before applying the service brakes. All with one brake pedal.