Mixed feelings about our first trip with trailer

[DieselDixon]

Well I just got back from our first trip with the Dmax pulling our 8000lb trailer and I have mixed feelings about the overall results.

First of all I must say I am mostly impressed with the overall trip, the truck was very stable during some fairly strong winds in both directions. On the way back we had a steady head wind of about 20 mph and although the truck kept the speed up (65mph) I could tell by the EGT and the boost that the wind was there. One big hill was a 7% grade for about 3 miles and she held 45 mph and none of the gauges even moved.

The 4wd worked good, got me on and off the beach with no problems and it was pretty chopped up due to the crowds and the tides not coming up high enough to flatten things out.

I guess the only disappointment was the fuel mileage. We traveled little over 500 miles and only averaged 9.1 mpg, far shy of the 16 mpg that the sales person said I would get whether I was driving around town unloaded or fully loaded and pulling my trailer. Not that I believed him anyway, but I was hoping to get about 12 out of it. Oh well, the truck has less then 3000 miles on it so maybe it will do better as it gets more miles? Never the less the comfort we enjoyed and the XM radio sure made it a relaxing trip.

[DonG]

DieselDixon,

I think one trip is too soon to determine your truck's potential. By the way: a 20 mph headwind is the same as driving 85 mph when you calculate mileage.

Give it some more experience on the highway.

Don

[56Nomad]

DieselDixon,

Yep.... Pismo was just beautiful on Tues., Wed, and Thursday.
Virgin dunes cuz the big winds smoothed them to perfection.
The weekdays...... everyone goes home. When we got there
on Monday, the sand was very loose and we had to air down to
10 psi to move the rig toward the dunes.

Of course we did the same 7% Cuesta Grade and on Thursday
we faced a 30 mph headwind returning home northbound on Hwy 1

In the past, with no wind issues, I got about 9.5 mpg on the trip to
Pismo with my 22 foot toy hauler plus toys and equipment which
is about 7500 lbs. The 8' wide trailer really creates a wind plow
and is not too aerodynamic.

This was our first trip down to Pismo with the Racor filter assembly
added and my mileage was 11 mpg on the way down and
10.5 on the way back. Not bad, considering the hills, weight,
headwinds and the big ass dually.

I pushed the petal to the metal on the Cuesta Grade and did not
drop below 55 mph...... but I also redlined it for a bit :rolleyes:

[Nixter]

Have you guys had your rigs weighed? It seems to me that I would get better mileage than that from my truck. I do think that one trip isn't enough to seal an opinion on especially with only 3k miles on the clock. I recently managed to get 20 driving empty with some old folks following. I really haven't isolated my mileage for a towing trip, (most of my miles are towing highway with some unloaded city mixed in) but my worst overall tank has been about 14. This was mostly towing my Bayliner 2452 HT which I believe to be in the 7-8k pound range loaded and fueled. With my river boat, 4 people and a ton of gear I can get 16 driving like a crazed lunatic on summer fuel, juice level 2. --Nick tongue.gif

[letsgo]

Wait until you have 20,000 miles on the truck then complain (unless you already do).

good luck

[peachin]

I am hauling 19,000 lbs, CGVW,
according to the Cat Scales at a truck stop. The only way you can tell the weight!

I drive with a Wind deflector which is worth 2mpg. I currently have 6500 miles. My best mileage has been 21 mpg, unloaded driving rationally. My worst mileage, loaded with lots of grades, tow haul mode with lots of breaking,
was 11mpg.

I guess, first find out what your real weight is.
Then I would learn how to use the Tow Haul mode -
there are many variations that will change not only your mileage but "heat" Also, don't push a hill because some guy on this site told you, you should be able to hold 55 or 65 - drive the power curve and temperature guages - if you have to go up a steep hill at 35 so be it!

I am driving stock - I am about to put on the
"Juice" but use it sanely - also I am going to add a pyroguage (egt's) and a boost guage.

I am very happy and I have 200,000 towing miles with 3 generations of Chevrolet diesels - This one is the best and is a work of art if you ask me.

[Bobcat698]

When pulling our 38 Foot Horse Trailer/Living Quarters we weighed on a cat scale at 25,000lbs Combined weight of truck & trailer.

On the way out to Colorado, the truck rarely shifted out of Overdrive unless it was a LONG hill.
In the mountains it down-shifted to 3rd & that was about it, we went around 52MPH all the way up.

It pulled well & we had a best tank of 13MPG & a worst tank of 8.48, which was the first tank pulling the trailer & we had a NASTY headwind.
Average MPG was about 11.5MPG.

Garrett

[DieselDixon]

So tell me why did I pay an additional $5k for a Diesel to get what I am assuming is the same gas mileage as a gasser? I realize diesel is a bit cheaper at the pump so there is a little savings and maybe I am judging this too soon (I sure hope so) but I am not seeing the benefits yet?

Speaking of the head winds, I did not state that my return trip, which I was averaging about 60 mph I only got 8.1 mpg. The best mileage I have got so far was 17.6 unloaded all highways. On average around town unloaded it has been about 13 mpg. I'll sit on my hands for a while and let the truck come to age I guess.

I do have another question, a few times during the trip it seemed that a fan came on at a high speed or something, but all the gauges where normal. It came from either the motor or transmission can anyone explain this?

56Nomad, yeah that is the beautiful thing about the winds; it makes those dunes smooth as glass for some great riding!

[DmaxCC6spd]

I too had mixed feelings about the Dmax pulling ability. The first tow with my truck was an enclosed car hauler. I had never towed anything with this kind of profile. It was loaded with stuff from an apartment, as I was helping someone move. The trailer was horribly tongue heavy, but I figured the trailer to weigh 4500 - 5000 pounds. Truck didn't feel as goog as my 99 2500 6.0 Silverado pulling my race car on an open trailer (About 5000 LBS). I couldn't believe that I spent this much money for something that pulled so poorly. I stopped at the cat scales and was I shocked. We crossed at over 15,000 pounds gross. The trailer well over 9000 pounds. It didn't help that the trailer was very nose heavy and only rated for 7000 pounds, hence the tires were all rather flat from the excessive weight. With all this in mind, I now know that I made the right choice in the Dmax.

[CanadaKev]

Dixon,
Don't kid yourself.
If you're gettin' 9-10mpg(heavy loads/lots of wind resistance), a 454 or 8.1 will be lucky to break 5mpg and will most likely be in the 3-4mpg range ;)
I ran 454's for years prior to the Dmax,(22-25K gcvw) and was always in the 3-4mpg range :(

The next time you hear that fan kick in, keep an eye on your eng. temp. guage and watch that needle drop ;)

Kev

[DieselDixon]

That's what I need to hear, I never owned a 454, only a 350 with a supercharger and I was getting 6mpg in the same situation.

The weird thing is my gauges never moved, the engine temp was always at 190-200 degrees and the tranny temp was always below 200. I was amazed that even the climb did not move the gauges, that is the one thing that impressed me. When that fan noise came on I looked immediately at the gauges to see if something was hot and they were all normal. Is that noise a clutch fan or electric fan?

I was surprised to see a separate tranny cooler in front of the radiator though. I read a couple of post that said that the tranny was only cooled through the radiator.

Don

[Lone Eagle]

Just blowing the rear tires to max is good for 2 mpg over the 45 I usually run in them. Wind will kill mileage more than all the hills in Utah. Later! Lone Eagle ;)

[roegs]

I just returned from the fist trip (1500 miles) with our '03 GMC 2500 HD CC D/A, and I was very pleased. The D/A replaced a '00 K2500 CC with 454 and 4.10 gears. We tow a Sunnybrook Travel Trailer that weighs 7660 lbs loaded. Tongue weight is just over 1000 lbs. We towed from Minnesota down to Branson, Missouri, and had some pretty good hills through the Ozarks. The performance of my D/A was awsome! Much better than my old 454. Part way through the trip, my wife asked why I always smiled when going up hills. It was wonderful...I actully passed semi's while going up and incline. Never did that withe the old truck. I ran between 65 and 70 mph for most of the trip, using cruise control for about half of it. Mileage was between 11 and 13, depending on headwinds and terrain. I run 65 lbs in the rear tires. Solo, I had one outing down to Arkansas with just under 21 mpg (filled both times at the same station and pump).

Highlight of the trip was the elimination of the infamous ticking. My truck had around 1800 miles on it when we left MN, and it ticked pretty good (I've done one oil change with Delvac 1300). Its quiet as can be right now. Maybe it just needed a good workout. :D

[Nixter]

DieselDixon,
I think what is happening is that the fan clutch is engaging due to the rise in underhood temps while your coolant temp remains stabil. Someone who knows better than me could chime in here but I will go out on a limb anyway. I think this is a normal operating characteristic and usually corresponds to the turbo intercooler nearing capacity. I have yet to see my coolant guage read over 210, and am pleased with how well the cooling works both engine and tranny. --Nick

[DogDays]

Dixon;
I have to agree with Nixter that the noise is probably the clutch fan coming on.
As to your mileage, I would not worry about it that much until your are up to at least 10-15,000 miles. I also had pretty bad mileage in the beginning (9 mpg towing 5er) and around 15,00 mi it beagn to get better. Now get anywhere from 10-13 mpg depending on weather and grades. Just driving back and forth to work (solo is 20-22 mpg). So, just hang in there for now, it just get's better and better with more miles. :D :D

[DieselDixon]

Thanks for the positive reinforcement guys, I feel much better about it now.

But like I said in my previous post I am extremely happy with this truck. It was the most comfortable trip we have made. I really liked how stable the truck was even though it was so windy out and blowing the trailer around so much. Also the breaks were a dream, there were a couple of times I had to do a hard break and the tranny started down shifting and I swear it did not take me any longer to get the rig stopped then it would unloaded. The XM radio was great, listened to the same station the entire way!

[motovet]

Been towing a 10,000# trailer for some time with this truck. In situations were you can keep the boost under 10 at all times the miliage can reach 12+.Others, such as the rendezvous trip with lots of grades and some wind, I could'nt break 10. Running empty I can get 20 on those rare occasions I don't get on it.The addition of the Juice was good for 1-2 MPG's in all situations. I also see steady guages during towing though the tranny will warm up a bit on long grades. Just say NO to gas!

[DIESELMAX403]

DieselDixion,

I too just finished my first trip pulling an 8000# travel trailer and I was expecting more power and better gas mileage even though I have only have 1500 miles on the engine.

As for power, I could not even go up a slight hill without decelerating. While traveling at 75 mph, I mashed the pedal when going up a hill and nothing happened. Only until it decelerated to 70 mph did it downshift into 3rd and then slowly picked up a few mph. I bought this truck and thought that it would be easy to pull my light 8000# trailer. I am afraid to go into the mountains.

Gas mileage was a pathetic 8.7 mph. This is the same mileage I got pulling with my 5.3 liter 2002 GMC Yukon XL (Suburban). And by the way, it held 70 mph going up the same hill. My Yukon XL is modified slightly with an exhaust system, cold air induction and high flow MAFS. Even with these mods it should not have near the power of the diesel.

As for temperatures, the engine did not budge from 200 degrees and the tranny from 190 degrees. I also had the fan noise come on and off.

Even though there is no check engine light on, I think I am going to take it back to the dealer to check it out.

[DieselDixon]

DieselMax,

At least I am not the only one in this boat; however, I don't think I am as disappointed as you. I was pretty sure the fan noise was normal, but I would have expected to see higher numbers in the gauges before it came on.

As for the slight uphill grades I did not have a problem with them at all. I locked the cruise control on 65 and it pretty much held it the entire way, on the slight grades it would down shift one gear and hold 60mph except for the 7% grade I went up at 45mph, only because that is where the truck felt relaxed. I probably could have hammered it down and got up to 55 on that hill, but why?

My philosophy is to get there and enjoy doing it. Although 65mph is above the posted limit for a vehicle pulling a trailer, the law does not seem to bother you too much if they catch you doing it, especially on the open highway. So as long as I can keep that speed I am fine.

Know if the mileage comes up a couple of digits I will be very happy with the results. I ran the AC the entire trip, had the XM radio cranked and loved every minute of the drive. Went about 300 miles on

[Dawg]

This is my first diesel. I have owned big blocks all my life. I routinely get 12-14mpg towing with the diesel. I am hard on the pedal and the truck and trailer fly over the passes. My big block would only get 6-8mpg, same trip. Best it ever got on the freeway, empty, with a tail wind was 14.7mpg. That was a one time deal! The Duramax/Allison wins big time!! At 20,000 miles is got even better!

[ 06-25-2003, 06:42 PM: Message edited by: Dawg ]

[Searay90]

Remember that there is another item that generates alot of heat when you pull those long grades......... the intercooler!! Yes your coolant temp guage may not move, but that turbo is compressing and heating alot of air when under full boost for sustained periods of time. That heat is removed via the intercooler. The fan clutch senses when there is excessive heat coming across it and locks up the fluid coupler inside and gets the fan spinning at engine speed (instead of freewheeling). That fan is designed to move alot of air and when it does it makes alot of noise!! Bottom line is that it is doing what it is supposed to do.

The reason you don't see the temp guage move much is that the general gave us a very generous cooling system with the DMAX and it is plenty capable of exchanging the heat that the DMAX generates.

[billnourse]

I pulled the 5th wheel through the mountains of Northern New Mexico weekend before last at a gross of 19,400. I got 10.8 and this was all mountains. My 454 would have gotten 6 and worked a bunch harder, with less speed. I handily passed a V10 gas Ford on one hill, and he did not have as big a trailer as mine. It wasn't that he wasn't trying either. He passed me going down hill about 75, then I passed him going up at about 65.

This is the first diesel I have ever owned, but I have pulled with several gas rigs, and overall, ther is no comparison. The diesel wins hands down.

Regards,

Bill

[earniem]

Dieselmax403 I dont know what you guys are doing traveling 75 mph with an #8000 trailer. I Know what that truck will do but that does not mean you have to do it. I know its fun but very dangerous. Be cool and safe and enjoy the truck for what it is. I pull a #11500 5th wheel at about 62 mph and If I have to stop I have control and can stop safely. These trailer( most dual axle type) are not set up to stop or handle the stress or balancedfor it.

[VFRRider]

I'm in the same boat as Dixon and Max, just took my 5th (approx 10000#) to the west side of Michigan. I expected the mighty max to hold speeds better over hills, she really could not keep speed. Now I never expected it to act like it wasn't pulling a trailer, but I expected her to have a bit more legs. The torque really shows itself off stops, no problem there, but I think my stocker wheezes a bit in the HP arena. I'm wondering if a box would make much of a difference?? Anyone know? Also my mileage has not been quite what I expected, even unloaded. 10K miles, and I'm gettin just under 16 city/highway mix, and got about 9-10mpg on the trip with the 5th. Not to be a complainer, I'm just demanding smile.gif . The truck was mucho comfortable, XM radio didn't drop a signal for the whole ride, and the DVD kept the youngins quiet for the whole trip (best $ ever spent).

[atvpilot]

Diesel Dixon,
I too owned a 98 1 ton Dually ext cab with the 454 big block and 410 gears before I bought my Max. Let the truck do it's time, it will improve as time goes on. I was getting if I was lucky 5-7 mpg with the gasser. I know get 16+ with the max. I bought my truck used with 27,000 miles on it and I was very happy to be able to go 2 weeks between fuel stops. With the big block I was on a first name basis and christmas card list with the owner of the gas station I was there so often. Be patient and give it time. You made the right choice and I am a first time diesel owner and don't regret buying this truck. One more thing, every time I get in the max I get this big smile on my face because it is such a treat to drive . It's comfortable and when you boot it, it pushes you into the seat and goes like hell.. See Yaaaa :D

[TopBanana 2500]

DieselDixon:
I haven't read this in the post for a long while but I still 'reset' my computer for the Allison by taking her up to 45mph (unloaded) and drop the gear shift lever all the way down to "L" (after I take my foot off the gas pedal) and let her downshift all the way. I do this 3 times before I hook up the 12,500# 5er and away I go. I feel this give's the tranny a new set point for towing.
I have never had a bad experience towing. It sounds like you need the engine looked at, or wait a while for it to break in. The fan noise is normal and I have hardly ever seen my rad. temp gauges move. I get an average of 11 mpg towing. I know I could get better than this but I tend to hotfoot it alot. EarnieM would be VERY disappointed in me if I mentioned how fast I pass up F*rds pulling trailers. He's right though... It is very dangerous pulling at high speeds. I have a hard time pacing myself whenI know I have a lot more power just dying to let loose. That's why I will never buy a Corvette.
Anyway... Just for S*its & Giggles, try the tranny downshift thing and see if it does any good. Just remember, it is really important to be on clean, dry pavement with no one in the rear view mirror when you do this! It's a little scarry at first but a piece o cake after a while.

[Lone Eagle]

VFRRider, What speed are you running? Have you weighed your 5the wheel. My single slide Wildcat 27RL goes 10K. Later! Lone Eagle

[ibelyea]

Last year drove from WA to Mich and there is not a hill (and I emphasize hill) from South Dakota to Mich that my truck did not stay locked up in 5th. That was with 12000 miles on it. This year with 27K
I expect to do as well if not better. I run in Level 2 and it just blasts up the hills and mountains of the Northwest. going to and from the Rendesvous this year averaged 11.3 MPG and the worst hill was coming out of Lewiston Id to Moscow. I could still maintain 53 in 4th from a standing start. The truck just gets better as it gets broken in. If you can't stay locked up and maintain 60 anywhere in Mich, you need to have your truck looked.

[DieselDixon]

Originally posted by DieselDixon:


We are going on an unloaded trip this weekend I'm interested in seeing what the mileage will be like unloaded on the highway. Just go back from our unloaded trip and got some very encouraging numbers. We went about 100 miles and averaged 19.7 mpg, I really like that mileage!

[VFRRider]

Lone Eagle I kept the cruise at 70, I know we shouldn't be towing over 65, but I have Semi's passing me at 70 as is. I haven't had my rig on scales, the 10K is based on dry wgt of 8100 lbs, GVWR of 11450. Overall length 32 ft, single slide also. I need to get it on scales to be sure. I ran up the west side of the state, which has some hills, east side of state is flat as a pancake. She runs like a beast now after the trip, lots of pedal mashing seems to have gotten the Alli into a mood. I'm probably will be picking up a box, would like da juice, but I'm not sure its worth the extra $ for mainly towing. Leaning toward a predator. Gotta make a decision before FL trip in July. Of course Exhaust, Air Filter, and Guages also. Hoping that will give it what it seems to be missing. Of course I've never been behind the wheel of a F*rd or D*dge so..

[Vette Racer]

I don't know what you'all expected but I've driven motorhomes with 454 motors and put up with 27 mph on the hills at 4.8 mpg and felt lucky to just get to the top. When you are pulling a big load it just doesn't get any better than a D/A. I pull a combined 23.5k, the mileage is usually around 9.5 depending on conditions, as low as 8.6 and as high as 11. Empty, right around 16.5. at 75. With this much weight what can you expect. The big thing is passing the semi's going uphill at 75 mph, thats the real blast! I tow with the juice set on level 3 most of the time and that's the way it works. If you are looking for towing power, get a D/A. If you are looking for gas mileage, get rid of your trailer and go buy a Honda civic. Thats my nickel!

[Dawg]

Just returned from a 500 mile trip with our trailer. We went to the east side of our state. On the trip over the mountains we had a head wind of about 30 mph most of the way. Temps were in the 80's. Mileage was 11.4mpg.

Upon return temps in the mid 90's. Pulled the Vantage Hill which is 10 miles long. The truck maintained 70mph very easily. Tranny temp did not go over 200*, water temp just touched 210*, 22.5 lbs boost, 1300* egt(pyro in exhaust manifold). The truck held 4th without hunting, clutch fan locked up. The truck felt very strong!! Had to slow a few MPH for some slower vehicles. I would ease down on the throttle and the truck would be right back to 70mph! I'm sure I had some more throttle but was happy with my current pace! The truck is stock except for the 265's. I couldn't be happier :D