Mountain driving question - RV-Dreams Community Forum

cherylbrv · RV-Dreams Family Member

Mountain driving question

Barbaraok · RV-Dreams Family Member

Yes, down shift as you need to to keep RPMs in the range that is good for your truck. Who cares how fast you are going - you go at a speed that is comfortable. Remember to come down in the same gear you went up. We normally find that 4th is a good gear for us, but have shifted down further if we need to. And if there is a question when at the top as to what gear to use, go with the lower one, it is always easier to shift up once you start down than it is to slow enough to shift down.

Barb

cherylbrv · RV-Dreams Family Member

This is an automatic transmission with Drive, 1st and 2nd gears. I recall that for a regular car, you're not supposed to drive in a lower gear over, I think, 20mph. Is it safe to shift into 1st or 2nd when going (or trying to go) over 50? And if I need to down shift, should I be doing it while in tow/haul mode, or does it not make a difference?

Sorry for my ignorance; we never towed anything before, and never drove anything larger than a minivan. Only had to use a lower gear when driving on icy roads in NJ, so this is all very new to us, and the owners manual doesn't really give much info.

The Bear II · RV-Dreams Family Member

If you have a tachometer the next time you take off from a start try to watch at what RPMs the transmission shifts gears. This will give you an idea of the RPM range for first second and final drive gears.

When going up hill with a load you will want to manually downshift to keep the RPMs up to avoid lugging the engine. You can go all the way down into first gear if needed but use the throttle to stay below the maximum RPMs you determined for first gear.

For example in my old truck on a 6% grade I had to use first gear. Second gear would cause the engine to lug and begin overheating. In first gear my maximum speed was 22 MPH to keep the RPMs at the right level. I used the throttle to keep from going over 22 MPH. If I exceeded 22 MPH the engine was over revving. There were times on steeper grades when my speed would get down to 15 MPH with my foot planted firmly on the floor.

It sounds like you should have been in second gear to keep the RPMS up. Also as the engine and trans heats up, if your engine is equipped with a fan clutch, you may hear it engage....it will sound like a jet engine is hiding under your hood. This is normal and the sound will dissipate as the coolant temperature goes down. Many an RV'er has thought something was wrong with their engine when they heard the fan clutch kick in and didn't know what it was.

With my 15000 lb 5th wheel and Chevy C4500, I'm lucky if I can do more than 45 MPH up a long 6% grade. Usually I end up in the 35 to 40 MPH range just for comfort and less stress on the drivetrain. Plus I get to see the sights and feed the squirrels as they run along beside my truck....tee hee

-- Edited by The Bear II on Thursday 23rd of April 2015 10:19:44 AM

Barbaraok · RV-Dreams Family Member

Cheryl,

Sorry about the gear answer, I get confused going from the MH to what is common for a truck. Principle is the same, manually down shift and keep the RPMs where you want them. Sounds like your exhaust brake did it's job just fine. So just learn your engine's sweet spots and you will be good to go. Like Bear II we enjoy the climb & descent at OUR speed, not what others are doing.

Barb

el Rojo and Pam · RV-Dreams Family Member

Cheryl,

Anytime I'm towing the 5th wheel I'm in tow haul, not just on grades. I believe Bear is talking about the RPM where your engine provides maximum torque, it should be in the manual. That's your target RPM when climbing.

cherylbrv · RV-Dreams Family Member

Forgive me is this question has been answered, but I'm just not seeing it.... when I downshift, should I also be in tow haul mode? Bear - how do I find this "sweet spot"?

Sushidog · RV-Dreams Family Member

Cherylbrv, you didn't specify what engine you have in your F-550.

If you have the 6.0l diesel, it makes it's peak 325hp at 3,300 RPM, with peak torque (570lb/ft) at only 2,000 rpm.

If on the other hand you have the 6.8l V-10 Gas motor it must be reved higher, to 4,750 RPM to get peak HP (355) and to 3,250 to get peak torque (455 lb/ft).

That gas engine must be reved-up to make it up the mountain. If you lug it up at a lower RPM (like you would a diesel) it will not perform well.

Here's a graph of the torque curve for the 6.0l diesel. www.internationalpowerstroke.com/60psd.html Notice it is a nice flat torque curve, making great power (500 lb/ft) from about 1,500 RPM to around 3,200 RPM, so try to keep it in this range while towing. The 6.8l V-10 has a pretty flat torque curve too (for a gas engine) but it makes its power at a higher RPM.

If you have diesel there are bolt-in tuners that can be installed to easily boost your power substantially for better performance when climbing. A word of caution though, those 6.0l Ford engines are known for blowing head gaskets if you haven't performed the high-performance head stud upgrade. Here's website that explains the reliability upgrades available for the 6.0 www.internationalpowerstroke.com/bulletproof-6.0L.html .

Chip

cherylbrv · RV-Dreams Family Member

It is a 6.0 and the previous owner did the upgrade.

Please confirm that I need to both down shift AND be in tow haul to get the best performance on mountain grades and that I won't blow something if I'm in tow haul (or not in tow haul).

Bill and Linda · RV-Dreams Family Member

Cheryl:

Anytime you are pulling the trailer you should be in Tow/Haul. That changes the shift points of the transmission for proper operation and best engine performance. Be in Tow Haul going up or down a mountain – or on flat ground. (BTW, unless it is after-market are you sure you have an exhaust brake? Tow/Haul or engine braking is not an exhaust brake.)

Many will tell you the transmission is “smarter” than you are as to what gear it should be in – especially going uphill. That said, if you watch the RPM’s you can sometimes help the situation by anticipating a needed shift going uphill and likewise use the proper gear going downhill providing increased engine braking. This takes a bit of experience and knowing your engine and monitoring the RPM closely.

Now here is the thing, the truck computer is supposed to keep you from going into a gear that would over rev the engine under any condition. That is exceed the maximum RPM limits of the engine. The operative words are “supposed to.” When you get to the Rally ask Howard about how that worked out for he and Linda with, I believe, the same type engine you have. He wrote about this extensively on the Blog. (BTW, with some engines the actual “red line” may be different under power or using engine braking. Mine is so engineered.)

I hesitated to post this but it’s important. One needs to be careful about exceeding the max RPM’s on any engine and especially those that have very limited RPM higher limits.

We’ll be glad to discuss this in more detail at the Reunion Rally if you or Mitch would like.

Bill

Sushidog · RV-Dreams Family Member

I would leave it in tow haul mode and not try to shift it manually, except if going very slowly up a steep grade where you want peak power.

Chip

cherylbrv · RV-Dreams Family Member

So unlike a regular car, it's ok to use a lower gear even if going above 10-20 mph, correct?

Terry and Jo · RV-Dreams Family Member

cherylbrv wrote:
So unlike a regular car, it's ok to use a lower gear even if going above 10-20 mph, correct?

Only if your engine RPM's are in the proper range at that speed. If you are over-revving, then you need to shift up. While our situation is a bit different, I recommend using the Tow/Haul feature when in heavy grades, both uphill and down. Going down, tap the break somewhere near the top of the summit and you may notice the transmission shift down. Let the Tow/Haul slow your descent, but if you notice that your speed is building to a range that is uncomfortable for your or is over-revving the engine, then press steadily on the bread and slow you speed by about 15 miles per hour. Then let up off of the break and let the Tow/Haul do its thing again. Repeat the breaking as needed until you get to better grades.

In our case, our Ford F450 has the Tow/Haul feature, but also a 4:88 rear differential ratio. That means that I can climb steep grades at a faster speed than what a lot of RV's can. So far, I've only pulled Raton Pass between Raton, New Mexico and Trinidad, Colorado with the coach, but I don't recall getting below 45 or 50 miles per hour on the ascent. On the descent, I think I only had to apply the brakes to slow down 15 mph about twice.

Terry

TheNewhalls · RV-Dreams Family Member

Check your owner's manual it might tell you the max and min RPMs for each gear. Like Terry I use Tow/Haul and brakes going down steep grades. I've yet to go down a decent grade where the Tow/Haul alone kept me at a speed I was comfortable with, so I will engage the brakes for short periods until I'm back to a comfortable speed or with-in my RPM range. I engage the Tow/Haul as soon as I crest the top of a hill, before I've had a chance to build up any speed. I've never used Tow/Haul going up a steep grade or on a flat highway. I'll have to try that going up a steep grade some time.

Bill and Linda · RV-Dreams Family Member

A word about Tow/Haul: The purpose of Tow/Haul is specifically to change several parameters in the transmission shift points (i.e. when it shifts) and also things like the torque converter lockup point – which improves, among other things, transmission cooling - temperatures. Tow/Haul will also delay shifts – i.e. hold the transmission in a gear longer – to prevent “hunting.” That is shift up or down more than is necessary which can be a real problem for diesel engines with fewer gears to work with than others – especially some older transmissions.

A read of the manual is always a good thing and I believe most manuals will tell you to turn on and leave Tow/Haul engaged anytime towing a heavy trailer.

The boys and girls who designed this stuff are pretty smart and they gave us tools to use when pulling heavy loads – Tow/Haul is one of them. I use it anytime I tow the rig and recommend same.

Bill

nomorsno · RV-Dreams Family Member

Agree with Bill 100% . When hooked up to the trailer turn on tow/haul and forget about it. The truck will do the rest. Just like the smart people he spoke of intended. If you shut off the rig then don't forget to turn on t/h again.

LandYachty · RV-Dreams Family Member

Cheryl

After we were with you guys in Arcadia we lost our tranny and had to have it rebuilt. Thank God for extended warranties. Just to add confusion. Here is what the tranny guy told us. Use the tow haul going up the mountains and no tow haul but the engine brake going down the mountain. It works for us in the mountains right now - but I don't know if a Florida tranny guy is an expert on mountain driving!

LandYachty · RV-Dreams Family Member

Cheryl

After we were with you guys in Arcadia we lost our tranny and had to have it rebuilt. Thank God for extended warranties. Just to add confusion. Here is what the tranny guy told us. Use the tow haul going up the mountains and no tow haul but the engine brake going down the mountain. It works for us in the mountains right now - but I don't know if a Florida tranny guy is an expert on mountain driving!

Lynn and Ed · RV-Dreams Family Member

Also agree 100% with Bill

When towing, we always have Tow-Haul turn "on" and put the Exhaust Break on "auto" (with our Exhaust Break options being On, Off, Auto). I am sure we may find some hills where we choose to solely select "on" for the Exhaust Break, but the auto setting has worked well for us.

Similar to other's responses, we also manually downshift (when going down hills) as needed.

MarkS · RV-Dreams Family Member

Remember, leaving your exhaust brake on all the time will shave off some fuel economy. It only takes a flick of a switch to turn it on if you find that you need it or want it. Let's say you are running on the flat, you let off the throttle because your speed is creeping up or you need to maintain your speed due to traffic. I'm talking about times when you don't need the brakes. The exhaust brake will kick in and slow you down shaving off speed that you spent fuel to acquire. You are going to have to use more fuel to reacquire that speed.

Terry and Jo · RV-Dreams Family Member

LandYachty wrote:
Cheryl

After we were with you guys in Arcadia we lost our tranny and had to have it rebuilt. Thank God for extended warranties. Just to add confusion. Here is what the tranny guy told us. Use the tow haul going up the mountains and no tow haul but the engine brake going down the mountain. It works for us in the mountains right now - but I don't know if a Florida tranny guy is an expert on mountain driving!

Jim,

You addressed this to Cheryl (and Mitch), but I'm not certain that their Ford F550 has an engine brake. Thus, if they don't, they do still need to either use Tow/Haul or have to manually drop to a low gear to begin a descent on a mountain grade and also use their brakes sparingly. As for the "Florida tranny guy," many of those advising to use the Tow/Haul in the transmission probably aren't from Florida.

Terry

Bill and Linda · RV-Dreams Family Member

Terry and Jo wrote:

Jim,
You addressed this to Cheryl (and Mitch), but I'm not certain that their Ford F550 has an engine brake.
Terry

The F-550’s do not have exhaust (or turbo) brakes and that includes the 2015’s. If the 550 has an exhaust brake it would be after market add-on.

Bill and Linda · RV-Dreams Family Member

Lynn and Ed wrote:
When towing, we always have Tow-Haul turn "on" and put the Exhaust Break on "auto" (with our Exhaust Break options being On, Off, Auto). I am sure we may find some hills where we choose to solely select "on" for the Exhaust Break, but the auto setting has worked well for us.
Similar to other's responses, we also manually downshift (when going down hills) as needed.

This is a good point from Lynn and Ed – The new “super” pickups and MDT trucks, like the RAM, Chevy, GM and the 2015 Ford, have turbo bakes that everyone, including the manufactures, are calling exhaust brakes. They do basically the same thing but are different as they use the variable veins of the turbo chargers to restrict exhaust flow. They are much more precise than the older – more or less on or off – exhaust brakes – such as a Pac Brake or the like.

The truck’s computers (ECM / TCM) work together and decide how much restriction to put in the exhaust path and can much more precisely control the truck’s engine braking ability – including letting the truck coast without significant restriction at speed. They're pretty smart.

Having the truck in Tow-Haul makes the turbo braking more “energetic" or aggressive which is very desirable with a big trailer.

IMO, once you have driven one of these newer trucks with a turbo brake in Tow Haul with a trailer connected you will really appreciate just how well they work. The RAM5500 Lynn and Ed have is especially effective in this area.

I’ve come down I-17 into Phoenix out of Flagstaff with the rig and never had to touch the brakes and I wasn’t doing 30 MPH. 50-55 was no problem to hold. Did the same last week down I-77 at Fancy gap - never touched the brakes. They really are effective.

FWIW

cherylbrv · RV-Dreams Family Member

It's a 2005 truck. As far as I know, we don't have exhaust brakes, only tow/haul.

chiseye · RV-Dreams Community Member

Put it in tow/haul and drive,thats what it is made for the computer will keep your rpm where its gets max pulling power. You wont blow nothing up going up or down a hill.

cherylbrv · RV-Dreams Family Member

Here's another question to add to this thread... when in tow/haul mode, can you also use cruise control?

TRAILERKING · RV-Dreams Family Member

Yes

ChefMom · RV-Dreams Family Member

cherylbrv wrote:
Ok, we had our first driving experience in the mountains last week (Smoky), which I'm told are very easy. We have a Ford F550 (4x4 automatic, with the tow/haul feature).
Bottom line question - when using tow/haul are you supposed to also shift gears (to a lower one) or should it do so automatically and you only down shift when not using tow/haul?
More specifically - while driving up the mountains, we couldn't get above 40mph even while flooring the gas pedal. It sounded like the engine was straining, but the RPMs were in the normal range and we're not really sure what it should sound like, so it could have been fine. Going downhill, we could feel and hear the exhaust brakes engaging and slowing down so I think that was ok, but I will ask the same question - should we also be down shifting in addition to using the tow/haul?

Our tow vehicle is also 4x4 automatic with tow/haul. We always use tow/haul when towing and were told by our driving instructor last weekend that to save unnecessary wear and tear on vehicle(s) that we should shift gears (while in tow/haul) according to the terrain.

Bill and Linda · RV-Dreams Family Member

ChefMom wrote:
cherylbrv wrote:
Ok, we had our first driving experience in the mountains last week (Smoky), which I'm told are very easy. We have a Ford F550 (4x4 automatic, with the tow/haul feature).
Bottom line question - when using tow/haul are you supposed to also shift gears (to a lower one) or should it do so automatically and you only down shift when not using tow/haul?
More specifically - while driving up the mountains, we couldn't get above 40mph even while flooring the gas pedal. It sounded like the engine was straining, but the RPMs were in the normal range and we're not really sure what it should sound like, so it could have been fine. Going downhill, we could feel and hear the exhaust brakes engaging and slowing down so I think that was ok, but I will ask the same question - should we also be down shifting in addition to using the tow/haul?
Our tow vehicle is also 4x4 automatic with tow/haul. We always use tow/haul when towing and were told by our driving instructor last weekend that to save unnecessary wear and tear on vehicle(s) that we should shift gears (while in tow/haul) according to the terrain.

" . . . always use tow/haul when towing and were told by our driving instructor last weekend that to save unnecessary wear and tear on vehicle(s) that we should shift gears (while in tow/haul) according to the terrain."

X2 Also provides better control of the vehicle coming down hill when in the correct gear. It saves wear and tear but also better controls speed and keeps the rig "tight" as we used to say in another professional life.

Bill

cherylbrv · RV-Dreams Family Member

What about - in addition to tow/haul and downshifting, using cruise control?

TRAILERKING · RV-Dreams Family Member

If downshifting...................Cruise OFF.

cherylbrv · RV-Dreams Family Member

Is it better to have cruise on and NOT downshift to maintain a steady slow speed?

TheNewhalls · RV-Dreams Family Member

If the grade is steep enough cruise control won't slow you down enough. It would be better to disengage cruise control and down shift to a lower gear, then use your breaks as you need them.

Bill and Linda · RV-Dreams Family Member

cherylbrv wrote:
Is it better to have cruise on and NOT downshift to maintain a steady slow speed?

Cheryl:

Short answer, no. If you wait for cruise control to slow you down (while towing) on a mountain or any particularly longer grade it is too late. Slow down – take your foot off the accelerator – and down shift before starting down a long grade. (I am specifically referring to pickup or light MDT trucks in particular like the F-550 or a 3500HD, etc.)

You need to give the engine a chance to control the speed in a lower gear. By the time the vehicle accelerates going down the hill and the cruise control says, “Time to down shift” it usually too late for it to slow the rig down as it too high a gear and in some cases can over-rev the engine in spite of the "computer" as Howard can attest. Doesn’t really matter what brand of truck, but especially if the truck does not have an exhaust (or turbo) brake.

Cruse control, while towing, is only for flat roads, not mountains or like going down - or up, IMO.

cherylbrv · RV-Dreams Family Member

Thank you so very much for the explanations. I'm starting to feel a bit more confident now in knowing what I'm supposed to do when driving in the mountains. Now, all I need is another chance to do so! :)

Trabuco · RV-Dreams Family Member

Once you climb and decend a few times you'll be a pro at it. Practice gives you confidence!

Camr · RV-Dreams Community Member

We always use tow/haul when pulling the coach. The only time that I manually shift is when pulling uphill and the transmission starts to hunt between gears. An example would be in 3rd gear, it upshifts to 4th, can't hold 4th and drops back to 3rd. I will manually select 3rd and back off slightly on the foot feed.
On the newer Rams, the auto setting on the engine brake (or engine "break" as it seems to be more commonly spelled lately on all the forums!) is wonderful. As long as you begin the decent at a reasonable speed, it is not necessary to touch the (wait for it) brakes. We have pulled 9% grades without any issues. The more I drive this truck, the more I love it.