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Discussion Starter #1
:confused: I am starting to look for a truck that will pull a 16,000# - 18,000# conventional boat trailer (not a load equalizing, 5th wheel or gooseneck) to replace my 2500HD.

The Monroe Kodiak conversion looks very inviting with the exception of the engine/transmission. I am having a hard time understanding why GM is putting the 300HP/605# version of the Duramax in this series when they put the 360HP/650# version in the 2500/3500 series. Both engines make their power at almost exactly the same RPM. It would seem to me the additional 55# would pull a heavier load better, especially since both engines make their peak torque at 1600 RPM.

Do any of you 4500/5500 owners have any idea why GM puts the lower powered engine this series? Additionally, why use the 5 sp version of the Allison when the 6 sp is available. It seems to me the 350HP/650#, 6 sp version would be a lot better.

Any other options available to pull 16,000 - 18,000 without going to the International CTX?

Thanks :)
 

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No Idead why they do this but I will tell ya I pull a 21' float with a case 450 loader and a bobcat @19750 and I dont have any problems U cant pull in over drive anyways. My self I think the ctx and the monroe conversion look goofy. I would have a flat bed put on it and not a pick up bed But this is me

Do as u wish
 

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I believe the Kodiaks do not have the LBZ option, only LLY. I also think the 6 speed tranny is too weak to use in a MDT. Mike L says they are not as sturdy as the 5 speed. "Which is just barely adequate for the power that you have on a stock motor."
Peak torque may be at 1600 RPM, but that is not enough rpms to keep up your speed unless you are pulling on flat, level highway. Get in the hills, and you'll be out of overdrive taching 2500+ RPMs just to maintain 55 MPH. In the mountains, 3000 RPMS just to keep up with the truckers.
 

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This question comes up again and again. The "commercial grade" MDT truck is generally sold to delivery companies that look at service costs and longevity. These are the Fleet buyers which make up the majority of MDT truck sales, non-commercial operators looking for "heavy pick-ups" to haul toys and such have little influence over engine ratings.

These engines are "down-rated" for fleet operators that submit their trucks to dozens of operators with varied skills and knowledge, shoddy or irregular service intervals, and mostly city traffic with lots of stop-go driving. The automaker determines the best engine TQ/HP tuning for longevity under these types of conditions, taking other factors under considerations, such as the up to 40K drivetrain (for pulling, up to 26K on straight-trucks), terrain (mountains, hills, off-road, snow, etc.), DOT/EPA/State regulations, and certain uses (Fire/Rescue, Plowing, commercial towing, etc.)

The argument that the MDT engine is identical to the Pick-up truck only goes as far as ordering a part. Though they are similar in designs, there are subtle differences that separate the two (mounting holes for brackets etc. are in different places, wiring harnesses are routed through different locations, and many parts have much stronger construction). The ouput shaft dia. is also much larger to accomodate the heavier clutch (handshakers) or TQ inverters (Ally). Looking under the hoods of both vehicles side by side, one can hardly tell that they are the "same engines" because of the external components and accessories' mounting locations. Underneath, the base components are (or appear) the same and functions mechanically the same way, but one cannot simply strip a part from a pick-up and be sure that it will fit the same on his/her MDT.

RF
 

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Radio Flyer,

Based on what you said with the ratings being detuned and with heavier parts would you think there is alot of harm then in upping the hp and torque with a tuner?
 

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Discussion Starter #7
Radio Flyer: Thanks for the info. I guess I was thinking of the Monroe/Kodiak more as a pickup on steroids than a true medium duty delivery truck.

A couple of more questions. If the 300/605 version is in fact more durable than the 360/650 pickup version it would seem to reason that using a tuner like Cowboydoc suggested you could increase the torque without reducing the reliability of the engine. Ever heard of anyone using a tuner on the 300/605 version?

What else is available in a pickup configuration besides the Kodiak or the International CTX that will comfortably pull 16,000" to 18,000#?

Shark Bait
 

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I use the Edge and a boost stick on my MDT. Only problem is the injector wire harness that everybody else seems to have at the moment.
 

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Shark,

The durability (to task) is because it is downrated. The stockier parts also add weight on the front axles, so much so, that it would render the LT trucks unuseable for carrying distributed loads across the axles.

I only want to emphasize that the two are different in design and specification, based on their intended uses. How many pick-up owners have 100K miles continuously loaded to max capacity? How many do this every 8-10 months at a time? Find one and you'll find 100 different fix-its and impromptu solutions for broken/sagging springs, beefed-up brakes, intakes, exhausts, air springs, brakets and braces to keep 'em together.

The right tool for the job the first time, is the only way to truly save time and money. You may find, as I did, that you'll wear out 3 3500 Duallies (2-year av. age at 150K miles ea. with resale/trade value of $3-5K in "like-new" conditions) for every one MDTs (2 year old at 500K miles has resale/trade value of 18K in "good" (best) condition....) Now, that's $50K (+/-) times 3 versus $60K only once. Doesn't that make business sense?

P.S. I enter different races than the Pick-up boys... Arriving at the destination without "white-knucke" experiences is worth more than the thrill of being first (with stained shorts).

RF
 

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Discussion Starter #10
Radio Flyer: You have some really good points, but my situation is a little different. I only put about 10,000 miles a year on my truck and I would estimate the when I get the new boat that I would only be pulling the 16,000 to 18,000# about 20% of the time. So I don't need a truck that can tow/haul maximum capacity for 300,000 miles.

When I pull a 16,000 - 18,000#, 10' beam boat it requires an Oversize Permit which requires you to stop at all weigh stations. IF a Trooper or Vehicle Enforcement Officer finds you are exceeding the manufacturers weight/tow limits you are in deep s**t., therefore I am looking for an alternative to a 2500/3500.

I am spoiled in that my 2500HD LT is a great truck. Essentially what I am looking for is a 2500HD LT, Crew Cab, Short Bed on steroids. What do I need?

O by the way, being a long time hot rodder and ex Air Force Fighter Pilot I believe there is no such thing as having too much power (in this case CUBIC INCHES).

Thanks Shark Bait
 

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Shark,

I understand (Ex-Navy Skywarrior flyer.....both retired). But performance comes at a cost, and it doesn't always mean raw power. Whatever power you have available must turn to "work" where the rubber meets the road. Dropping a C16 into a chassis requires a lot of engineering, and they are available (KWs, Petes, Intls, WSs, Volvos, etc.), especially in the suspenssion and drive-train, but for this sort of displacement WEIGHT becomes a problem. It means a heavier front axle/suspenssion/brakes (air) on the front to support 8,000 lbs. or more engine and accessories, which combined with the drives would take you over the magic 26,001 lbs. Meaning CDL, logbook, IFTA, etc.

If that's not a problem for you, then it may be worth you looking into used HDT's, such as over-the-road (OTR) tractors, dropping the center drive axle, moving the rear axle to center, cutting down the frame for a standard 9-11 ft. tow-body built. You can easily find 4-6 year old Volvo 610 or 630 with a large CAT rated at 450-500 HP and over 1000 lbs. torque for under $25,000.00 (but its a given that it will most likely have 1/2 Million mile on the Odo.)

Were I to rely on a tractor to move oversized loads up and down the coast, and I needed more than what I've got now, I'd spend the additional $20K for a spec'd C7500 (Cat C7, 300hp/860tq, Ally 3000 RDS). I guess I just don't miss wearing a G-suit all that much and Cats and Traps always made me nervous, so I settle for getting to destination on time, economically, and safely, over the thrills and excitement of speed. Too many close calls in the air has made me more cautious on the ground, I guess. Never having enough "power" is an inconvenience and has little consequence...not having enough TRUCK though, often translate into chewing on seat cushions and grip marks on the wheel....

I don't question your piloting or pre-flight skills, but being that I've trained and used the "Smith System"* at all times, my power calculator is based on a different equasion.
P.S. Hope all this helps, we Old Crows have to stick together and thank you for your brave service to our country.

RF
 

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I love the idea of having a 2500 or 3500 with the 7.8L inline 6-cyl. motor. Why doesn't Chevy offer this option? Currently, it is only offered in the 8500, right? Of course, the 6.6L V8 Duramax could lay down the same torque as the 7.8L if a power programmer was used, but I'd prefer the inline 6.
 

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M'OW,

The 7.2 CAT & 7.8 Duramax sixes is available from the 2-1/2 (6500) and up, and range from 210 HP/540 TQ to 300 HP/860 TQ. Either of these easily exceed 4K lbs, and with trans. attached may add another 1400 lbs..... THAT is why they don't use them in the 1.5 & 2 Ton MDT's, too much front axle load. Certainly more axle load than the light truck's are capable of.

The V-8 DMAX allowed GM to build a truck to fit the commercial Mid-Market which was dominated by Japanese COE's for decades (Nissan/UD and Isuzu) with small displacemet 4, 5, and 6-Cyl power-plants with 100-200 HP/245-365 TQ.

RF
 

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Thanks, Radio Flyer, for the info. I suppose the 6.6L would be the best of choice anyway since there is a strong aftermarket for that platform. With the 7.8L, there probably is not too much, so the owner would be stuck with just that amount of torque. With the 6.6L, the more torque can easily be added. I just love the sound of the inline-6 but don't want to buy a Dodge to get it. The sound, smoothness, and torque of the 7.8L inline-6 seemed to be just what I'd dream of having IF I could have it in something smaller than an 8500 (like maybe a 4500 even). Do I need it for commercial work? No. Would I use it for towing?... but only a race car and equipment. I'm just addicted to torque and the sound it makes!
 
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