Question on RPMs and 'redlining'

tsunami · 11-11-2009, 02:58 PM

My unit sits on a Ford Chassis with a V-10 Vortec engine with auto-transmission. Does anyone know what the 'redline' rpms are
for the V-10 engine.
We were recently going through Steamboat Springs, Colo. and came down a very long, steep grade. I put the transmission into low and let the unit
slowly take me down. The transmission was really whining.
I happened to stop in at a local Ford dealership and the service manager said
that 'it is impossible for the engine to redline in first gear while
coasting downhill! He stated that the only way to redline the engine
was to hold down the accelerator until the engine built up too many rpms."
Is this true?

NWJeeper · 11-11-2009, 06:30 PM

We have the V10 too in our rig and this was our first experience with the Ford chassis and engine. While descending a pass using tow/haul mode and our Jeep in tow it ran upwards of 5000 rpms which sounded and seemed very high. However I have also noticed it's propensity to kick down on mountain passes and revving just as high when pulling up the grade. While it does seem disconcerting to the ear it never the less is the way it was engineered and therefore should present no problems. I have never yet seen the water or transmission temperature gauges do anything other than stay pegged in the middle even in the heat of Arizona either. I also don't recall seeing a "red line" on the tach but it tops out at around 7000rmp (I would have to go out and look to be sure). I don't know if there are govenors in place to prevent over-revving on these engines or not, perhaps a Ford expert here could tell us.

TulsaSteve · 11-11-2009, 08:13 PM

Google knows all...

http://forums.truckinweb.com/70/6461...v10/index.html

Per the link.. redline = 5250 and at this point the fuel flow is reduced.

Regarding the downshifting, I just use the tow haul mode and let the computer figure it out. Well that and the US Gear UTB that I have on my Saturn. In more serious braking, that Saturn gives me a tug.. It's a very nice feeling when your trying to stop.

LadyWindrider · 11-11-2009, 09:48 PM

This day of computer controlled engines, there isn't a "REDLINE". The computer is in control, and there is a "rev limiter" that will kick in when max rpms are obtained. You can go out, start your vehicle, hold the throttle flat on the floor and not hurt anything. The computer would control spark and fuel and you would here the engine starting miss fire, and do what is called "bounce" off the rev limiter.

tsunami · 11-14-2009, 12:28 AM

Thanks for the responses...but...

One responder mentioned his tack was running at 5000 RPM, another
mentioned an 'electronic redline computer limiter' at 5200 RPM.
A Ford dealer did mention that the engine will limit itself at about 5000 RPM and 'limit' fuel flow to keep the RPMs below 5000.
But these situations are for when the engine is pumping fuel through the injectors.

My Toyota shuts off the injectors when the downhill grade is steep. The engine closes off the fuel and uses compression to help control the speed.

My question really was about downhill 'coasting'...is the engine compression enough to limit the RPMs to less than 5000 if the engine's fuel is essentially shut off...but the grade is so steep that the unit still wants to accelerate?
What happens if I am in low gear going downhill, my foot off the accelerator, and the RPMs exceed 5000? Will the transmission rip itself to pieces?

The Ford service manager could (would?) not tell me what would happen.

If I were in such a situation, do I let the transmission burn out, or the brakes, trying to negotiate a very steep, long grade?

TulsaSteve · 11-14-2009, 09:47 AM

Quote:

Originally Posted by tsunami

Thanks for the responses...but...

My question really was about downhill 'coasting'...is the engine compression enough to limit the RPMs to less than 5000 if the engine's fuel is essentially shut off...but the grade is so steep that the unit still wants to accelerate?
What happens if I am in low gear going downhill, my foot off the accelerator, and the RPMs exceed 5000? Will the transmission rip itself to pieces?

The Ford service manager could (would?) not tell me what would happen.

If I were in such a situation, do I let the transmission burn out, or the brakes, trying to negotiate a very steep, long grade?

Burn out the brakes. The computer will handle the tranny and engine. Your only concern should be for you and the family. Let the tranny and the engine blow/seize/burn/fall out.

If you are actually burning out the brakes, I'm guessing that your coach is WAY overloaded or your brakes need serviced. These systems are designed to handle the GCWR under all reasonable driving conditions, not much more.

Get concerned when you crest a hill and you see dozens of RVs, semis and 5th wheels in a HUGE pile at the bottom. A clear sign of a civil engineer that had a VERY BAD day.

LadyWindrider · 11-14-2009, 10:59 AM

Well, you can't compare your Toyota xxxx to your Coach. Too many differences to start to mention. Learn to drive in the mountains if that's where you are going. When your tach reaches 5000, use to the brakes to bring it under 3000, then let off the brakes and let the engine build back to 5000, then the brakes again.
(tach numbers are for reference only and your vehicle may need to operate under different conditions) Don't expect the engine, the trans, or the brakes, to do the WHOLE job. You have many resources you are responsible for as operator, so learn how to use them all together. There are other post on here about mountain driving, search them out and read them, and search other places also. It's not a Toyota, and will require a lot more skill to drive safely.There will be little forgiveness, only a pile at the bottom of the hill.
I apologize if it seems like I'm ranting, I'm not, only trying to keep us all safe while on the highway with each other.

TulsaSteve · 11-14-2009, 03:39 PM

The Ford chassis is a great combination. Trust the engineering.

Imagine being in a Semi. manual downshifting, trying to save your air brakes, working the jake brake, trying to remember what your load is today.. We have it easy with the Ford F53 chassis.

I ALWAYS run mine in Tow Haul mode. It's designed for towing and for hauling heavy loads.. Well I'm always hauling a HEAVY load... It's a 38 foot RV!

So keep the speed reasonable before you crest the hill, have tow/haul on and use your brakes. The computer will do the rest.

Just to be extra safe I spent a little extra on my TOAD braking system. Went the with Unified Tow Brake from US Gear. With my Saturn attached, I have 10 wheels of proportional full POWER braking. I stop much easier / shorter with the TOAD than without out.

Feels nice going down a steep incline, stop sign getting closer and closer and then you feel the Saturn tug you backwards

tsunami · 11-15-2009, 01:18 PM

My Sunseeker has a Ford E450 chassis rated at 20,000 lbs.
I have weighed my unit (wet) on a truck scale: 15,000 lbs. So my unit
is actually underweight by about 2 1/2 tons.
When I bought my unit, I knew that the unit weighed much less
than its max. vehicle chassis weight limit.
The Steamboat Springs downgrade is about 7% for about 7 miles (2500ft/36000ft).
I had assumed that using a V-10 engine on an 'underweight' chassis
would give me a significant lee-way on steep downgrades via engine
compression. I was surprised that the engine could not handle
a 7% grade in low (first) gear...I had to pull over and let the brakes
cool off half way down!
We now map our mountain trips so that we never go down a grade which
exceeds 5%!

TulsaSteve · 11-15-2009, 01:57 PM

Wow... That's some grade / distance.

How did you know the engine couldn't handle it? Engine/Trans temps peg the needles?

Did you have Tow/Haul on?

Also if you forced it into 1st gear and you couldn't keep the speed low enough, it may have upshifted to protect the drivetrain.

From what I've read in the chassis manual, I got the impression that I should run with Tow/Haul all the time and leave it in Drive. The computer apparently senses the amount of braking from the pedal and uses that to determine how much engine braking to do.

Sounds like you have zero weight problems, so hopefully there is a way to adjust your approach to avoid issues.

TulsaSteve · 11-15-2009, 02:29 PM

I pulled my manual.. (you got me thinking about this situation)...

I have the 5 speed tranny on a 2007 chassis. Page 183-185 covers driving/trans operation for my tranny. The way I read it, I should stay in "D" with Tow Haul and work the brake to stay at a safe speed.

Link to the manual that I've been using:

http://www.motorcraftservice.com/pub.../07f23og2e.pdf

LadyWindrider · 11-15-2009, 09:37 PM

Truckers rule of thumb "whatever gear it takes to go UP and whatever rpm you run in that gear, that's the way you come down. Example : it takes 2nd gear and the best rpm you can get is 2500, then you come down in 2nd gear. When the rpm gets to 3000 rpm, use the brake to get rpm to 2000, then let off brake, (so they can cool) and let rpm build back to 3000. Then brake again, etc., etc, until you reach bottom. Keep your rpm 500 above, then brake until 500 below, what it would take to pull the same grade. Sometimes this must be done by trial, especially if you haven't pulled that hill. You can time how fast the rpm's build, and if it's too fast, ie the brakes don't have time to cool, then you might need a lower gear. If it's too long, then you might need a higher gear. If you are on the brakes 15 seconds, then you need to off of them for 15 ~ 20 seconds. Speed adds another factor, that may require a different gear selection. The idea is to split the braking required , letting the engine/trans do half, then letting the brakes do half. Hope this helps.

By the way, couldn't get to your link, error said I must log-in.

TulsaSteve · 11-15-2009, 09:54 PM

Sorry about the link...

Try this:

https://www.fleet.ford.com/maintenan...ls/default.asp

Then put in your year, Ford, and the closest match. For me, I used the F-550.

LadyWindrider · 11-15-2009, 10:14 PM

Thanks, now that I've seen the manual, sounds like TOW/HAUL will work most of the time. Again will depend on the grade and the weight of your rig, and the speed you feel safe running. I usually use the posted TRUCK speed as a guideline, and try not to exceed it by much. I don't have tow/haul on my F150, so I manually select a gear, usually at the top of the hill or just before, while still going slow, before things get out of hand. Also good to be down a gear or two at the top, in case you made a wrong selection, your brakes are still cool and you can get slowed down enough to select a better gear. One last thing, don't worry about the traffic behind you or the horn blowing. They'd really rather be going slow than not at all if you spill your rig all over the road. The horn won't hurt, and neither will the gestures. I even enjoy being shown I'm "number 1" sometimes. (hope we can all laugh at this).

NWJeeper · 11-16-2009, 10:46 AM

Quote:

Originally Posted by windrider

I even enjoy being shown I'm "number 1" sometimes. (hope we can all laugh at this).

Hey, the government has used a lot of your tax dollars turning me into an a$$hole and I'm proud of it. I take it as a compliment. In my line of work there is no room at all for ambiguity and therefore I say it as I see it.

I will proudly stand along side ya windrider...

tsunami · 11-16-2009, 07:17 PM

Again...my surprise was the inability of the V-10 engine to provide enough engine compression to keep my unit down to essentially a slow crawl! On the Steamboat Springs downgrade, I had the transmission in low (first) gear...and the transmission never tried to upshift (and I wouldn't have wanted it to). I wanted to keep the speed down enough so that I would have time and enough braking left to pull over and stop if I had to. Some people were passing me, going downhill, at least 70mph and I could hear their tires squealing on the curves! My nephew (a truck driver) was with me and cursing my V-10 engine and kept saying "see I told you, you should have bought the diesel with a jack-brake!"
I was once in Wyoming following a TT being pulled by a small pickup and they burned out their brakes on a long downgrade. They said that they had down shifted to first gear and the combo kept trying to break the speed limit in first! They decided that
they would stay in first even if the trans burned out. Everytime they upshifted to second, the combo wanted to shoot ahead. They thought that they were going to go off the road.

TulsaSteve · 11-16-2009, 08:01 PM

Quote:

Originally Posted by tsunami

Again...my surprise was the inability of the V-10 engine to provide enough engine compression to keep my unit down to essentially a slow crawl! On the Steamboat Springs downgrade, I had the transmission in low (first) gear...and the transmission never tried to upshift (and I wouldn't have wanted it to). I wanted to keep the speed down enough so that I would have time and enough braking left to pull over and stop if I had to. Some people were passing me, going downhill, at least 70mph and I could hear their tires squealing on the curves! My nephew (a truck driver) was with me and cursing my V-10 engine and kept saying "see I told you, you should have bought the diesel with a jack-brake!"
I was once in Wyoming following a TT being pulled by a small pickup and they burned out their brakes on a long downgrade. They said that they had down shifted to first gear and the combo kept trying to break the speed limit in first! They decided that
they would stay in first even if the trans burned out. Everytime they upshifted to second, the combo wanted to shoot ahead. They thought that they were going to go off the road.

Sounds like you've got a bad combo. Sell it and go with a diesel since that's what you'll trust. You probably were going too fast to actually be in 1st gear. My bet is the computer upshifted for you. You won't answer my questions so I'm guessing you don't like the answers.

Assuming that, you probably didn't have Tow/Haul on and you probably thought the engine was "overrevving" because it was too loud for what you thought was safe. My guess is that you haven't read the manual and probably won't. Please sell the rig before you wrap yourself around a tree and blame Forest River. You could probably sit on that hill all day and watch F53 chassis come down it without a problem.

Happy trails!

NWJeeper · 11-16-2009, 08:58 PM

Quote:

Originally Posted by tsunami

Again...my surprise was the inability of the V-10 engine to provide enough engine compression to keep my unit down to essentially a slow crawl! On the Steamboat Springs downgrade, I had the transmission in low (first) gear...and the transmission never tried to upshift (and I wouldn't have wanted it to). I wanted to keep the speed down enough so that I would have time and enough braking left to pull over and stop if I had to. Some people were passing me, going downhill, at least 70mph and I could hear their tires squealing on the curves! My nephew (a truck driver) was with me and cursing my V-10 engine and kept saying "see I told you, you should have bought the diesel with a jack-brake!"
I was once in Wyoming following a TT being pulled by a small pickup and they burned out their brakes on a long downgrade. They said that they had down shifted to first gear and the combo kept trying to break the speed limit in first! They decided that
they would stay in first even if the trans burned out. Everytime they upshifted to second, the combo wanted to shoot ahead. They thought that they were going to go off the road.

Tsunami, it's not just the V10, it's ALL gas engines. I have never driven an RV yet with a gas engine that WILL hold you on a 7 percent grade! I'm not even sure a diesel would do it either unless it had a jake brake. I really don't know why you expect the V10 to do it. Our Chevy 454 in the last rig we had would warp it's exhaust manifolds to the point of letting the exhaust gas burn through the spark plug wires if you tried to use compression only to keep your speed in check.

It comes down to the fact of proper driving technique as eluded to by Windrider and Steve. It is the reason why you see large semis on steep passes doing 10mph down hill and using their breaks prudently to keep their speed in check and the engine from over reving.

I think you have unrealistic expectations. There are several of us here driving MUCH bigger rigs than yours with the same engine without problems. I suggest as the others have to read your manual and learn to drive your rig correctly.

It also sounds like those folks in Wyoming had a truck too small for the trailer they were pulling, that's not the trucks fault but unfortunately it's a condition we see all to often on our trips. Rigs overloaded, guys pulling full size SUVs with their motorhomes that are probably at least 1500lbs over the rated tow capacity of the motorhome, etc, etc.

tsunami · 11-17-2009, 08:05 PM

I was trying to relate my surprise concerning the action of my V-10 rig on a steep grade.
Rather the responses I received on this forum were "shut up or go out and spend another $20,000 for a diesel"
I guess that I will shut up...I certainly don't want to interact with the people who seem to populate this forum!

TulsaSteve · 11-17-2009, 09:11 PM

Quote:

Originally Posted by tsunami

I was trying to relate my surprise concerning the action of my V-10 rig on a steep grade.
Rather the responses I received on this forum were "shut up or go out and spend another $20,000 for a diesel"
I guess that I will shut up...I certainly don't want to interact with the people who seem to populate this forum!

Might be best for everyone. Folks here like to ask questions to get more info so they can advise you. We provided you a link to the manual, offered ideas about Tow/Haul and suggested that being in 1st gear may have been wrong. Given all of this feedback, the premise of your question about redlining in 1st gear is probably wrong.

Since you won't provide any feedback other than to talk about someone unrelated guy and his travel trailer and your buddy that wants you to have a "jack brake" (btw it's called a Jake Brake), your probably not a good fit for this forum.

Link regarding the Jacob Brake in case you're interested:

http://www.jakebrake.com/products/ho...rake-works.php

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