Newbie needs help knowing when to downshift in mountains

[Rich-n-Linda]

GA Navigator, you are right on with your assessment of car manufacturers and advertised HP. The same thing happens with our motor home diesels. For example, the Cummins ISL is offered in various HP ratings from 350 to 450 HP. It's the same engine, and the torque spec is the same for all of them. Only the max operating RPM is different.

I am very familiar with diesel locomotives...I've been running them for years. I had a long career in the railroad industry as a locomotive engineer and as a company officer in the Operating Department. The very popular EMD 645-E3, 3,000 hp diesel engine turns over at a maximum of 900 rpm when running flat out in throttle position 8. To develop 3,000 HP at only 900 RPM the diesel engine develops almost 17,500 foot-pounds of torque! No wonder those motor mounts are HUGE!

However, if we substituted a diesel that could only develop 5,000 foot pounds of torque, but we could spin it at 3,150 RPM, we would still have 3,000 horsepower.

How about a torque rating of only 1,250 foot pounds, like the ISL? If we could spin it up to 12,600 RPM and maintain that torque spec, that would also be 3,000 horsepower. But I don't want to be within shrapnel range if you try it! ;-)


Rich & Linda

[nothermark]

Originally Posted by frankdamp

Modern transmission control computers know what's most appropriate - why bother messing about with the shift?

Because the computer cannot see the road ahead. The driver needs to do the planning the computer cannot do!

[ga traveler]

Originally Posted by JFXG

ga traveler, I was addressing snickers, the OP. ge came with a diesel.rge1285 with his V10 jumped in and piggybacked.

Snickers has a 30 ft airstream land yacht according to his profile. I don't think they came with a diesel.

[TBS-POPS]

I find it amusing all the info being spewed here and the OP has yet to divulge what power train he is dealing with to get him the best answer he could get. Carry on.....

[Crasher]

Originally Posted by TBS-POPS

I find it amusing all the info being spewed here and the OP has yet to divulge what power train he is dealing with to get him the best answer he could get. Carry on.....

That's because some of us have all this information stored up in our memory bank and some of it has to be released as facts to make room for what we might want to store tomorrow.

[cc8375]

Just another note on a steep grade down I put the Gear shift lever in 2nd gear for decent. On such a grade you a topping out at 50 mph or less at the top. The last 3 - V10 fords will hold 45 - 50 mph down hill on a steep grade in 2nd Gear, braking when the coach reaches 50 mph, I brake to slow down again to around 45 mph.

[tropical36]

Originally Posted by cc8375

Just another note on a steep grade down I put the Gear shift lever in 2nd gear for decent. On such a grade you a topping out at 50 mph or less at the top. The last 3 - V10 fords will hold 45 - 50 mph down hill on a steep grade in 2nd Gear, braking when the coach reaches 50 mph, I brake to slow down again to around 45 mph.

Sounds like you're on the interstate and not quite the same as coming off of say, Powder River Pass in the Big Horns and making a descent into Buffalo, WY for example.... Cloud Peak Skyway Scenic Byway - Wyoming Travel and Tourism
It was either here or coming down into Cody from Yellowstone's east entrance that we saw a runaway ramp with big spring loaded gates every so often and built out over a cliff to nowhere. I can't even imagine having to use that thing and have never seen one before or since. This is what can happen if you pull over to let your brakes cool sometimes and in fact, boils the brake fluid without the cooling air, no longer rushing by.... Motor home crashes into Buffalo store, Arkansas man killed - FOX16.com
As would be expected, there's a brake shop at the bottom and on the outskirts of Buffalo that does one h.....of a business and the owner told me, he has seen it all....

[khogle2]

To George 1285 who has a 2012 V10. Here are the horsepower and torque curves that represent your newer V10 and the GM 8.1 that is out of production. These are supplied by Bluebird bus and are representative of your motor home engine.

Snickers 1 looks to have a model I am not familiar with, and I'm not sure what it is.

Ford spent a lot of time and calibration hours making the tow haul mode as effective as possible. I would use it to your advantage. The V10 going up a grade, will run quite frequently at 4,000 rpm (above the torque peak of 457 at 3250 rpm). That is by design.

With this gas setup, it has plenty of cooling. It does not have the same issue as a diesel does when the driver operates the engine at too low an rpm under load.

Use the tow haul mode up or down hills.

Keep the speed way down going down the hills. Just go slow.

[snickers1]

thanks for the info but I still do not know when to keep unit in OD or Drive?


I finally found out what motor I have, WORKHORSE CUSTOM CHASSIS, 340 HP/ 190” WHEELBASE/ 18,000# GVWR, AUTOMATIC 4-SPEED OVERDRIVE

[cc8375]

Originally Posted by tropical36

Sounds like you're on the interstate and not quite the same as coming off of say, Powder River Pass in the Big Horns and making a descent into Buffalo, WY for example.... Cloud Peak Skyway Scenic Byway - Wyoming Travel and Tourism
It was either here or coming down into Cody from Yellowstone's east entrance that we saw a runaway ramp with big spring loaded gates every so often and built out over a cliff to nowhere. I can't even imagine having to use that thing and have never seen one before or since. This is what can happen if you pull over to let your brakes cool sometimes and in fact, boils the brake fluid without the cooling air, no longer rushing by.... Motor home crashes into Buffalo store, Arkansas man killed - FOX16.com
As would be expected, there's a brake shop at the bottom and on the outskirts of Buffalo that does one h.....of a business and the owner told me, he has seen it all....

Descent, such as this would probably be in 1st gear....... cresting a 2 mile High mountain, mostly likely you would be in 1st or 2nd at the top, descending in one lower gear.

Snickers as well as myself are on the East coast. Most likely we'll only get maybe one Such trip to such a beautiful place. Hopefully descending safely!

[dateem]

I have a 2001 30' with same engine/transmission. Also have same 8.1 in my 06 Avalanche 2500 and use same techniques in it when towing. On the flats and easy driving, I use the OD. Whenever getting to a hilly area or pulling a strong headwind I shift to D. Same thing on really winding roads where corners range from 55 down to 45 or even 35, shift out of OD for better control. This raises the rpms just a bit, and probably drops mpg, but makes the unit more responsive to throttle and less need to hard brake. As many have said in previous posts, on hills I am pretty much in D but if rpm starts to drop I shift to a lower gear. Down hill staying in D most of the time keeps the speed down and I can minimize use of hard braking. Will shift lower if necessary.

I hope you enjoy your coach as much as we are in ours. I always had TT before, used to build Beaver Coaches in mid 70s and finally having an AS is pretty darned cool.