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Old 08-31-2008, 03:06 PM   #1
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Pulling Power On Hills

I know gas vs. diesel has been done to death but I have a simple question about diesels. I have never driven one and know nothing about them other than the get better fuel mileage than a gas engine and have more pulling power. I currently tow with a 1999 3/4 ton Suburban with a 454 engine and it pulls great. I pull a 1978 Ambassador (28ft). It seems that even on fairly mild hills my vehicle downshifts and my mileage goes to pot. I have a Scan Gauge and can monitor my fuel mileage in real time. I understand that diesels have great pulling power at low RPMs. Does this mean that they don't downshift as often on mild hills?
Thanks,
Tom
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Old 08-31-2008, 03:36 PM   #2
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Hello:
I have been pulling 31' Classics with a 06 and most recently an 08 Ford Super Duty Diesel and would not give up the pulling capacity of the diesel versus Gas. We hit the bottom of a hill at 60mph and go over the top at 60mph without any problem. We have been averaging 13-15 mpg depending on the terrain. Even with the price disadvantage of diesel vs gasoline, we feel we are ahead of the game. Will be quite a while to make up for the cost of the engine, but I like the power that a diesel gives me. Hope this gives you some insight.
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Old 08-31-2008, 04:07 PM   #3
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I have a 2006 super Duty gas. The new 5.4 liter 3 v paer cylinder. It also has a 6 speed tranny. 4:10 axles. Deisels do tow alot and they have a loyal following. They say if you drive more than 17000 miles a year a deisel will pay off in the long run. I drive over 17000 miles a year. I chose gas. Biggest reason. I didnt want Ford first year 6.4 liter. My Tranny (6speed) was something to get used to when new I had to goback to the dealer for a updated program in the computer. Now this thing doesnt search, and in Tow Haul mode the tranny stays in gear with out the old downshift to get RPM's up. It is amazing how far these trucks have come in the last few years. When decending down a grade if the computer sees I am applying the brakes it will downshift. I get 12.5 miles to the gallon towing my Airstream. I get 10 with my 24 foot box trailer at about 11000 lbs.
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Old 08-31-2008, 04:07 PM   #4
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Quote:
Originally Posted by rochar3 View Post
Hello:
I have been pulling 31' Classics with a 06 and most recently an 08 Ford Super Duty Diesel and would not give up the pulling capacity of the diesel versus Gas. We hit the bottom of a hill at 60mph and go over the top at 60mph without any problem. We have been averaging 13-15 mpg depending on the terrain. Even with the price disadvantage of diesel vs gasoline, we feel we are ahead of the game. Will be quite a while to make up for the cost of the engine, but I like the power that a diesel gives me. Hope this gives you some insight.
Bob
And remember, if maintained properly, you can expect a MUCH longer lifespan out of that powerful diesel engine - which MORE than makes up for the higher upfront cost, IMO.

At least, that is what I am banking on! '08 Silverado Crew HD w/Duramax Allison combo - even splurged for leather so the seats would last as long as the engine

Will let you know if another 400k miles or so!
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Old 08-31-2008, 04:34 PM   #5
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Originally Posted by tlavergne View Post
...Does this mean that they don't downshift as often on mild hills?...
there may be too many variables for a yes/no answer.

the gearing (final and 1-4), programing, incline, wind, entry speed, tire size and WEIGHT of the load...

along with the power/torque curves unique to each power plant.

along with the drivers FOOT.

these are just a few issues, the automotive wizards can add to this list.

anytime the tow'd load, incline and speed are matched to a given power band, shifting will be less frequent.

some of the turbo diesels have a broad/flat peak torque curve and that reduces shifting, as i understand it.

many newer trucks have 2 or more tranny programs, like the tow/haul mode...

on the ford this feature RAISEs the shift point, so a given gear is held longer going UP and DOWN inclines.

the 'shifting' u mention can be reduced by dropping the tranny into a lower gear before the the hills.

this might be a good thing in areas with many rolling hills with lots of incline variation.

the single best gear or driving style to max out mpg is widely debated,

and the best towing reports all are suspect. (i get 81.6 mpg by adding old motor oil...2 my salad dressing)

while the scan gauge may provide instantaneous fuel consumption data...

keep in mind much of the UPhill loss is recovered going DOWN the other side,

unless punching the throttle and mashing the brakes is part of the driving style.

driving INto the wind or stopngo do more damage to mpg than hills when averaged...

cheers
2air'
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Old 08-31-2008, 05:27 PM   #6
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All,
Thanks for the responses. I tend to tow at 60-65 mph anymore. The transmission does not hunt, when going up an incline it will downshift and stay there until the hill has been crested. And yes, I do make up the mpg going down hill. This past summer in W. Virginia I was getting 5-7 mpg going uphill and up to 35 mpg going down. It was fun to watch. But, as is with the stock market, it is probably not wise to keep a constant watch on these things...it will drive you nuts. I am in the process of thinking about replacing the '99 3/4 ton Suburban in the next 5 years or so...got to wait until the kids are out of college. Until then the Suburb is fine. A lot can happen in the tow vehicle world in the interim. Who knows, in the end I might just keep the Suburban. I just wish it got a bit better mileage when not towing. But I can buy a lot of fuel for the cost of a new truck.
Tom
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Old 08-31-2008, 05:46 PM   #7
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A 3/4 ton 'Burb with big engine will tow most any Airstream just fine, what with heavier suspension, bigger brakes and ring gears, etc. You WILL get more torque out of a diesel and that MAY give you less downshifting, depending as 2Air says, on so many factors that it'd take a big computer to sort them all out. But there's nothing wrong with downshifting - "it's supposed to do that." I love my diesel ('08 Duramax, Allison trans, etc.), and it gets pretty fair mileage and yes, I like the tow / haul mode when in hills, and all that. But if I'd had a 3/4 ton 'Burb when I started out, I'd have probably kept it, given the additonal cost of a new vehicle.

Well, maybe not - I haul stuff like generators and fuel and my wife is always hauling trees and bushes and piles of manure, etc. Long ago, I had a 1/2 ton 'Burb, and loved it, but I wouldn't haul fuel and such inside it and the manure, etc. was NOT a good inside-the-vehicle load. Trust me on this one. So my pickup is just fine. YMMMV. Literally.
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Old 08-31-2008, 08:36 PM   #8
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diesel

I drove gasser's for years got my first diesel and loved it so much all my vechiles are now diesel. I drive a VW Bettle TDI it gets 45 miles to a gallon and climbs hills without down shifting. My Duramax 2500 HD is the best tow rig I have ever had. I love my truck!
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Old 08-31-2008, 08:54 PM   #9
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I kept my '01 Dodge so long the leather driver's seat gave out at 600,000 miles but the engine is still strong at 678,000 miles!

Godspeed,
Trent
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Old 08-31-2008, 10:20 PM   #10
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Hey Blacksheep my buddy owns the local garage and he like you also loves his dodges. You both have alot of miles on um. Thats cool. Gas or deisel they both definatly have there place.
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Old 09-02-2008, 07:21 PM   #11
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my 2001 dodge diesel does downshift occasionally when going up steep grades but not anywhere like my gasser does. This is my first diesel and definitely not my last. IN fact if I could change all my vehicles to diesels I would.
I recommend you go test drive a diesel and see how you like it. 3/4 ton Burb's are cool. I just wish you could get one with the Duramax and allison combo.
my towing mileage is roughly 14-16 mpg plus when I keep her at 1600 rpm /1700 rpm at 62/65 mph
hey blacksheep, 678,000 miles? that is fantastic.something to be said for the dodge inline 6 cummins
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Old 09-02-2008, 08:47 PM   #12
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I agree about wishing they put the Duramax/Allison in Suburbans. That would be a sweet combo. I know earlier Suburbans had a diesel option but it was only offered for a few years.
Tom
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Old 09-02-2008, 10:09 PM   #13
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I have heard in the next couple of years alot of the contacts are running out. Dodge /cummins Ford/ Intl ect.. I heard catterpillar is throwing its hat in the ring also. 2012 alot is going to change detroit engineering has said
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Old 09-02-2008, 10:19 PM   #14
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I don't know that you'll recoup the dollars spent on the diesel option unless you keep the truck for the long haul. I'm towing with the Duramax 2500 HD and I'll never go back. With steady freeway driving as a commuter I get 20.6mpg and it averages out around 17 with stop and go. Towing with full load I'm getting 12 to 14 mpg depending on the hills and traffic. I've never met a hill that I can't top out at 70 mph or more. I don't let myself get stuck in the slow lane uphill.

The tranny is steady with butter smooth shifts. No neck jerking searches for the right gear, no huge jumps in engine rpm. It just flat-out pulls and let's you sit back and enjoy the ride. 70 mph at 1750 rpm.

Large block gassers pull but I'm not certain that they have the longevity of the diesel engine. I've heard that the diesel will far outlast the large gasser. So, in fact when you're rebuilding the large block gas engine, the diesel will still be going... you make up for the difference right there.

I'm a previous VW TDI owner and love diesels. I loved that little engine... I just didn't love the car around it.

Test drive one today and feel the smooth power of the diesel.

The Duramax/Allison is probably the quietest most reliable diesel/tranny combo on the market right now.

Cummins are fairly noisy and the Ford/Navistar Powerstrokes are coming off a few years of reliability issues. Watch out for used Powerstrokes.

yakman
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