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Discussion Starter #1
I deliver high profile ‘fire safety’ trailers. Traded the GMC Duramax/Allison I’ve used for over two years on a Dodge Cummins/6 speed. Just returned from my first tow with the new Cummins. The run was PA. to Texas and back. Five days and 3,200 miles later here’s my comparison of the trucks.

Both trucks are 2500 models, extended cab and crew with standard beds. The Dodge is a heavier truck. Its hitch receiver sits about 5 inches higher than the GMC and its suspension seems to have more heavy-duty spring assemblies. The Dodge also uses 17 inch 265/70 tires with more load capacity than the 16 inch 245’s used by GM.

It’s hard for me to compare two engines with different transmissions. The Allison automatic with the Duramax engine has pulled many trailers for me all over the country. This combination seemed more than adequate in power but always suffered the maddening ‘downshifts’ on hills and into headwinds. This immediately raises engine speeds into the 2,800-rpm range. Upon downshifting I usually slowed the truck down to the low 50 mph range to limit engine speed and noise. Much of my driving involved attention to throttle positions that would minimize these downshifts. With the hill and headwinds I experienced on this tow, my guess is there would have been hundreds of downshifts with lots of attention, fatigue and stress trying to avoid them.

After leaving Pennsylvania for West Virginia my astonishment with the Cummins was just getting under control. Pulling a hill out of Wheeling I did my first downshift to 5<SUP>th</SUP> gear. I’m not sure it was needed but the truck only had 300 miles on it and I didn’t want to lug the motor. All the way to Texas and I downshifted just one other time coming up a hill out of Cincinnati. Think about this. For the first time I could sit back, turn on the cruise control, hold my speed and just pull hard all the way. I am still in disbelief. Man, the Cummins just pulls the hills flat in 6<SUP>th</SUP> gear. There is almost no sound from the engine or turbo on even the longest hills and overall speed drops very little. I am guessing my average speeds all day are 5 to 10 mph faster while towing with the Cummins than with the Duramax.

Towing comfort and safety involve many issues. More power makes for easier towing but ride issues must also be considered. The GMC truck was easily moved around when big trucks passed. . You had to always be alert because the sway wanted to move you into the passing trucks. Not with this Dodge. There is almost no sway. At times I got scared seeing a big truck so close, not feeling the sway and not really hearing it as I used to. The higher speeds on hills also reduced the number of times a big rig was able to pass me. Chalk one major win up to the Dodge in the area of stability and this was also true in strong cross winds.
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I'm glad your happy with the decision you made,and it's working out better then anticipated .... What kind of fuel economy did you get ??


Mac
 

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Discussion Starter #3
Mackin,


Remember, I was happy for 117,000 miles and then things went out of control with the Duramax. Time will tell.


The fuel computer seems to be with 2 tenths of a mpg. correct. It also looks like the filler is 'repeatable' with regard to refilling the tank. Under tow I got around 9 mpg. on this trip. The trailer was one of those 12ft. 'boxes' that goes 8,000 lbs. If you designed a trailer for bad aerodynamics this would be it. Once I deliver they never leave the local community so aerodynamics is only a problem for me. High headwinds and storms sometimes had me under 8 but never over 10 mpg. The logs on my Duramax for this same type of trailer going to the same places showed a low of 7.9 mpg and a high of 9.4. No difference.


The return ride was different. The Duramax gave me about 18 to 19 mpg at 75 mph. This Cummins started at 18 but was doing over 22 mpg. as I neared Pennsylvania. I think it's breaking in.


Going to San Diego after Thanksgiving. That should give me a better handle on just what the fuel mileage is.
 

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Discussion Starter #5
Wickedsprint,


I was hoping you would have some experience to relate with the 6 speed in the Duramax. Two GM dealers I delt with never had or ordered a Duramax with 6 speed. I had no experience with it and never ever even saw one.
 

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I have a buddy with a crewcab longbox 4x4 duramax/6speed, he pulls a 28ft gooseneck enclosed cargo trailer, usually loaded with antique furniture. He doesn't have alot to compare it to (it replaced a '91 Dodge cummins/5spd) but says that it towed pretty good stock, and with the Juice, it's like there's not even a trailer back there..


Definitely doesn't have the low RPM torque of the Cummins though. He says it's definitely alot faster on the hills but needs to be revved like a gasser (in stock form).
 

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Captain where do u call home ?


PA or is that where the trailers are?
 

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Discussion Starter #8
DMAX TIM,


I have a house outside Apollo, Pa. and some property here. I also have a house on The Little Manatee River where it flows into Tampa Bay. The community is Ruskin, Florida.


May through early December I live in Pa. The trailers come out of Mt. Pleasant, PA. Mobile Concepts is the company. December through May I live in Ruskin where I am a charter captain part-time and still pull trailers but only South to the Gulf Coast and Florida.


Changed oil in the Cummins today. Simple, simple, simple... and the big Fleetguard filter cost $7.74. Bought a fuel filter also....$13.19.
 

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I replaced my 2001 Dodge HO 6 speed with a 2003 Duramax. Chose the Duramax because my wife wouldn't drive the 6 speed and we would travel for 4-6 weeks pulling a 13000 lb Cariage 5th wheel.


I thought I was crazy because with an additional 55 HP and 40 or so more puond/feet of torque the Dodge seemmed to be much stronger.


I always towed in 6th grar and almost never needed to downshift to th but the Chevy just seems to be unable to stay in 5th going up relatively mild grades.


Does any other converts feel the same way?
 

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I think it's the difference beween a manual and an auto. Tell us about a Cummins with an auto.
 

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I had a 2000 reg cab cummins/6 spd. On long highway runs, I could approach 28-29 mpg. That was cruising at 70-75. Over that, and it dropped to about 15.
Anything past hull speed, and you're just burning fuel. Drivetrain was great, except the front end only had three zerks - upper balls and one on the track bar. Saved time greasing... Awesome power. Those six big cans dish out the grunt. The truck around the drivetrain looked rugged, but the tin was soooo thin. My father has a 2001 HO/6spd. My truck was not an HO - queer model year - 2000 sales were down, so they ended the model year early. Both good trucks.


I'm on my second Duramax, and I see no need to go back. Next one will be a stick...


Ty
 

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They cut 2000 models short because they used up all their emmisions quota.
 

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I've got a good friend with a truck like yours. It's a 2003 Dodge 2500 Cummins/6SP. The thing I like about his truck is that it is loaded with leather and other goodies and he could still get the stick. That's why I believe this is my last GM truck eventhough it's a great one.


I have the stick with my Duramax and it's great. I don't think I'll own another auto for the reasons stated above. I've pulled trailers to and from New York and North Carolina and left the truck in 6th gear. Heck I still haven't driven a Duramax/Allison combo. I'm sure I'd be disappointed.
 

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What's the difference between running an Allison with a locked torque converter in T/H mode and a manual? Gear ratios? Power loss because of the complexity of the Allison, and the fact you are running a hydraulic pump inside of it?
 

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Discussion Starter #16
Pick,


The Allison will not stay in 5th gear. That's the difference. Minor upgrades and headwinds will have it shifting into 4th. Cruise control is useless.


There are many transmission reflashes that address this issue. There is also the possibility of a 'fuel box', like Juice, to help also. It will take some time, money and effort to control the towing downshifts. My experinece does not include the Juice. All else I tried was just some varying degree of failure.


For towing heavy loads the Allison does not work well and then you have the reliability issue.
 

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Power loss and the TCM forcing a downshift.
 

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Capt, I'd say chalk another one up for stick shifts. You're mileage empty is about like mine with stock tires. With a smaller displacement you should get even better mileage once broken in. Pulling 5K with the cruise on my 6spd just goes. The only hill I've downshifted for is a 6% grade.


I've driven Allisons in APC's and semis. They are great and you can't beat them for what they do but it comes at a cost of more power required to turn them. Even locked there is still a lot of extra stuff whirling around sucking up Hp. The semi I drove had a 400 Hp Series 60 and weighed 50K empty. An 80K loaded 300 Hp truck with a 9 spd could easily out run me...but get me in the sand the stick didn't have a chance.
 

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Discussion Starter #19
Jeli,


Your comments have me thinking back to my original decision on selecting the Allison. With the 6 sp I may still have......


"Don't look back. Something may be gaining on you". Satchel Page
 

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I enjoy my duramax as well as anyone.. I feel these are by far the best choice if you're looking for making a stock truck go fast with tuning only... I do have to say my 99 powerstroke would pull my heavy trailers much better.. It's kinda hard for me to compare though.. The ford was a dually with 4.10's and I usually pull now with 3.73's and 35's.. There's no comparison in speed and mileage though.. I'm usually empty, so the D/A is by far my choice.. If I were a constant puller, my choice may be different... I'm sure all the different choices have their own strong points.. Competition is a great thing...
 
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