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  • dustykdustyk Posts: 2,926

    I'm afraid that I don't have enough information from people that I've talked with to help you with that exact comparison. However, just from the physics of the comparison, I would say that is not a likely scenario. Assumming all other things being equal, a V8 running through a 3.92 axle ratio will fire (approximately) two more cylinders than a V6 coupled to it, per tire revolution. That means burning more fuel regardless of other factors, such as load.

    The only other recent Dakota that I've driven to compare with my 2003 4.7 Club Cab Sport Plus with the 3.55 axle, was a 2003 3.9 Club Cab SLT. Now I am uncertain which axle ratio that particular vehicle had. Since it was an SLT I suspect it had a 3.21 ratio, which I believe is standard, but I am unsure. But it also had much smaller tires, too. That vehicle was noticeably tamer than my 4.7. I know and have talked with a number of people who have Dakota 3.9s and they are generally reflecting a 2-3 mpg better gas mileage than I. One person I know quite well gets 18 local and has recorded a high of 24 highway. I don't think you'd get those numbers with a 4.7 and a 3.55 axle. A 3.92 is going to be worse.

    I've towed my ATV (650 lbs) around now for almost a 1000 miles. I own hunting property in the southern part of the state and the trip has a fair amount of hills, including a few "killer" grades. My Club Cab with the 4.7 and 3.55 gears has handled the job admirably. It's got more than enough power, even in those situations. Compared to a F150 Supercrew and a RAM Quad Cab that I drove on the same route, my Dakota downshifts a lot less on those hills. Unloaded it never needs to downshift.

    Now, the opinion of power is subjective. What may be more than adequate for me may not for you or your circumstances. If you drive a lot in hilly country then maybe a 3.92 axle will benefit you. Lower axle ratios will not change your low speed or around town (local) gas mileage that much. Where you're going to see real difference is highway mileage. Your rate of towing is a little higher than mine so maybe your circumstances make a lower axle ratio a more viable consideration.

    Consider how many miles you're going to put on this vehicle and estimate the fuel cost difference assuming a reduced mpg factor. Let's assume you'll drive 10,000 miles a year and get 16 average mpg. That's 625 gallons of fuel. If a 3.55 axle will get you 17 mpg, that's 588 gallons of fuel. At $1.60 a gallon (western New York State prices) that's about $60 less a year in fuel cost.

    That was only an example. I (we) don't know for sure what the delta will be for the axle ratio difference or your particular driving situation. But this might give you a method to estimate the total financial impact.

    Good luck and keep us posted on how you make out.

  • bookittybookitty Posts: 1,303
    Bill and Dusty, Bill may not be too far off in his summation regarding fuel consumption of the 3.9 versus the 4.7. The 3.9 is a marginal choice for a truck the size and weight of a Dakota (especially a quad) and towing "compounds the felony." I too have had reports (strictly anecdotal) that the 3.9 equipped Dakota is not fuel efficient. Dusty, your equation regarding the factor of 2 additional cylinders firing per revolution sound simple enough, but there are many other influences that are not being addressed. One, being that the 4.7 is a more efficient design in of itself. Other issues are displacement and perceived load (perceived from the point of an engine). I have the 4X4 Quad with 4.7. 5 speed and LSD in 3.55. I tow on occasion a very HD 5X8 utility trailer, or flat tow my wife's Jeep Wrangler. PA is always hilly (although western PA is very very hilly) and I never have experienced a shortage in power. Now, on the other hand, if I were say a landscape contractor who towed constantly, I would definitely opt for the 3.92 (with the 4.7 or even the 5.9 if necessary). When I was shopping for a crew cab small truck, I test drove a Nissan Frontier. I drove the truck (with the salesman along) and hooked up my empty utility trailer. This was prior to the turbocharged engine, and it felt like I was "riding" the brakes. I never tested the turbocharged equipped model, but exhaust driven turbochargers do not really gain boost until sufficient RPM is realized. No off of the line "grunt." Bill, if you could possibly try a "tow" test ride, you would gain a better sense what feels right.

  • dustykdustyk Posts: 2,926
    Bookitty, thanks for the reply.

    Yeah, I've heard the same thing about the 3.9 and some low reports as well. But I've also noticed that when I talk to older drivers I almost always get reports of much higher gas mileage from the 3.9. Like I said earlier, most people with the 3.9 are reporting 1-2 mpg better than I for city, highway, and combined.

    (When my son bought his '91 Dakota in '93, he complained that his pre-Magnum 3.9 didn't get very good mileage, although he did no worse and had more power and more truck than the two S10s he owned previously. Anyway, on one trip down to the property I drove both ways. We got 27 going down and 26 coming back. This is a 3.9, 5-speed manual, 6000 GVW conventional cab.)

    I understand your comment about load and efficiency, but I don't believe the efficiency difference is that wide. Even if true, as I said earlier, "all other things being equal," two more cylinder firings per tire revolution is going to burn more fuel. How much more can only be a contention since there are a number of factors that will impact this. My 21.87 may be the best my 4.7 will ever do. I don't know. But I do know some with 3.9 automatics that get 24 and better.

    Since the EPA ratings do not show a huge gas mileage advantage with the 3.9, I think your basic point is valid, however. And when driven hard under load the point may be even more acute, since most 3.9s come with the 3.21 axle ratio.

    I, too, find that my 4.7 with the 3.55 ratio still supplies plenty of reserve power on hills when carrying a load. I wouldn't even begin to consider opting for the 3.92 ratio if I ever did this over again. In fact, if they offered a 3.21 I'd might consider that. Of course, I don't tow that much. About 6% so far, and that will drop since hunting season is over.

    Best regards,
  • haselhasel Posts: 64
    I had a 1999 Club Cab with the 3.9l V-6 3:92 rear the Average gas milage over 21767 miles was 18.56 MPG best milage 22.8 MPG, on my 2001 Q Cab with the 4.7L V8 3:55 rear ave gas milage over 17947 miles is 17.55 MPG best milage 21.8 MPG. I live in northern NM , the 3.9L joust did not work here in the Mountains.
  • (bookitty,dustyk,hasel) Thank you for the replies and valuable tips.

    There's certainly a lot of factors to consider when deciding upon the final drive axle ratio. The following EPA figures are from the energy guide printed on the window stickers of both vehicles. The 3.9L with 3.92s prints it as 19 mpg city and 26 highway. The 4.7L with 3.92s lists it as 20 city and 27 highway. I know these are under ideal conditions and we likely can not duplicate them. Now, these figures are also in Canadian Imperial gallons (which is slightly larger than a U.S. gallon). Personally, with my 3.9L QC with 3.92s coupled to a 42RE 4-sp auto has not done better than 24 mpg highway and city combined 50/50. My worse mileage has been 17 mpg city (90%). This is with a K&N replacement filter installed with no other mods.

    I have to agree with Norm that the next gen 4.7L is of better design (semi-hemi) over the 3.9L LA series engine which has served DC well for decades. I understand the 4.7L H.O. on the Jeep Grand Cherokees are even better with the newer pistons, composite intake manifold, forged crank, etc etc. I guess it really boils down to needs as both of you have identified. One has to live with the gas mileage and performance when we are not doing any towing. (personally preference, I guess) Given the good power of a 4.7L engine, I believe I should be happy with 3.55s mated to the 4.7 but, others say, "...if I already have the tow pkg and the HD group, get the 3.92s or you will be sorry later going up a steep hill with a load..." I guess it's decision time...

    Thanks again, you guys are GREAT!
  • dustykdustyk Posts: 2,926

    >>(EPA) The 3.9L with 3.92s prints it as 19 mpg city and 26 highway. The 4.7L with 3.92s lists it as 20 city and 27 highway.<<

    These look like 5-speed manual transmission figures. Is that correct?

    >> Personally, with my 3.9L QC with 3.92s coupled to a 42RE 4-sp auto has not done better than 24 mpg highway and city combined 50/50. My worse mileage has been 17 mpg city (90%).<<

    This actually is pretty good, based on what others have told me. My daughter's 3.8 Explorer has never gotten over 18. My nieghbor's S10 Blazer has never gotten over 19. I've had 3.9 auto conventional cab owners give me the same results. And that is probably with the 3.21 axle. I have had two individuals tell me that they have gotten as high as 27 with their 3.9 autos. But, like you, most owners are within the 20-24 highway range.

    Well, maybe I'm wrong about the 3.9 and its more of a slug than I thought. I trust the EPA ratings more than anything else.

    Unless you're driving is highly concentrated in hill country, I think you'll be quite pleased with the performance of the 4.7 and 3.55 axle.
    Of course, I might be more easily satisfied with horsepower. If you can, test drive both combinations if at all possible.

    Best of luck,
  • (dustyk) "These look like 5-speed manual transmission figures. Is that correct?"
    > No, both were auto transmissions. All things being equal, I would think a manual trans would get better mileage due to timely shifting by the driver. <

    The EPA gas mileage figures quoted were from window stickers on 4-dr Quad Cabs having auto trans with LSD and 3.92s. The only difference is the 3.9L V6 uses the 4-spd auto, 42RE, as compared to the 4.7L which uses the 5-spd auto, 5-45RFE. These mileage figures are also quoted in "Imperial Gallons", which is slightly larger than the U.S. Gallons. Hence, the numbers may look low. For example, 1 Canadian Imperial Gallon is equivalent to approximately 1.2 U.S. Gallons.

    Well, personally, I would hate to see what the performance of a 4-dr Quad Cab (over 4K lbs) would be like with a 3.9L V6 coupled with 3.21s going up a very steep hill. (even empty) However, the gas mileage would be great.
    Thanks, Dusty.

    Yes, I'm going to try a tow test against both configurations (as Norm and yourself have suggested) Guess what I'm doing this weekend?

  • dustykdustyk Posts: 2,926

    Gee, that 27 highway doesn't sound right with the automatic and 3.92 gears. My 2003 Club Cab is rated 15 city, 20 highway with 3.55s and 545RFE. I believe that the same truck with 3.92s was 14 & 19 when I was shopping.

  • sunburnsunburn Posts: 319
    I think we are comparing apples and oranges here. The Canadian "EPA" numbers are different (higher) than the US EPA numbers. The two agencies use different tests to arrive at their mileage figures. I don't think that there is any way to convert between the two.
  • steve234steve234 Posts: 460
    First, the number of cylinders has nothing to do with fuel effficiency. The factors that matter; are engine efficiency, transmission power conversion and rolling resistance. Add driving style, traffic conditions, weather, etc. They developed a V12 221CI engine years ago that got 50% better gas mileage and more power than equivalent V6 & V8 engines. The pistons were the size of teacups. The cons were that it took a long time to warm up and it was too expensive for mass production. If it was more cost efficient to make V8s smaller than 4.0L, V6s would be rare.

    I drive both the 3.9 & 4.7 and they both get about the same mileage, but I can tow with the 4.7.
  • (dustyk)
    Dusty, I'm only quoting mileage figures from what is displayed on the window stickers for the configured vehicle. Please keep in mind these are in Canadian Imperial Gallons and are for Quad Cabs built in Warren,MI. for Canadian consumers. They list the 4.7L with 3.92s, 5-45RFE 5-spd auto, as 20 city/27 highway. For the 3.9L engine, with 3.92s, 42RE 4-spd auto, they list it as 19 city/26 highway.

    I believe the conversion factor is 1 CDN gal = 1.20095 US gallon or conversely 1 US gal = 0.8326738 CDN gallon. Therefore, my highway 27 mpg is equivalent to your 23 mpg (approximately) and my 20 mpg would be approx your 17 mpg.

    Merry Christmas and Happy Festive Holidays to ALL,
  • bookittybookitty Posts: 1,303
    Bill, I'm surprised that the ratings in Canada are not in kilometers as opposed to miles per any gallon.

  • (bookitty) Norm, yes, I was surprised too.

    To confuse everyone, the factory quoted the Kilometreage differently on their window stickers. In their wisdom, they presented it slightly different to us in Canada. By that, I mean, they listed it as "x many Litres of fuel consummed for 100 kilometres travelled". To get the Miles per Gallon figure, one has to look it up in an EPA energyguide table quoted in Imperial Gallons. For example, 10.1 L/100Km Highway is 27 mpg (Imperial Gal) or 23 mpg (US Gal). (i.e., that's 10.1 litres of fuel used to travel a distance of 100 kilometres). I've done a fair amount of research recently to make my deision and all the window stickers appear to be consistent for each vehicle configuration.

    BTW, I concur with you that the 4.7L engine is a much more efficient engine. Hence, is why it uses less or similar amounts of fuel as the 3.9L (given same benchmarks). I think the Power Tech 4.7 H.O. (260HP) is even better but, only available on the Jeep Grand Cherokee Overland or JGC Limited editions.

    Merry Christmas and Happy Festive Holidays!
  • bookittybookitty Posts: 1,303
    Bill, the 4.7 was also introduced via the Jeep. It reminds me of the Oldsmobile, which was the "test track" vehicle for GM. Thank you for your warm wishes and a happy and safe holiday season to you and yours.

  • marsha7marsha7 Posts: 3,703
    Sorry to be so long in responding, but I finally got back to this topic...thanks for your words on the "slant six" situation.

  • need diagram of R&R fuel injectors on 1989 dakota 3.9 L. w/TBI 2x4 please help!!!!!!!!!!
  • Hi Folks,

    Does anyone know if Chrysler is going to extend incentives into the new year? I know that the current offering from Dodge runs out on the 6th of January.

    Thanks for the help,

  • dustykdustyk Posts: 2,926
    Don't know. It might be difficult to second guess them, besides. I bought my Dakota on 9 October, a week after the $1500 rebate ended. Sure enough, they resumed the rebate (or zero financing) on 1 November in this area.

    I did better than $3400 off the list price on a $23,000+ Dakota, so I think I got a fair deal. Maybe I could've done better, I don't know.

    Good luck,
  • 2003 is supposed to be a bad year for the car makers. The incentives currently offered have supposedly caused a million plus people to get into the car market earlier than they planned. Therefore there is expected to be a million plus people who would have bought in 2003 to be out of the market because of the 2002 purchases. As long as GM keeps up the incentives Ford and Chrysler pretty much have to keep up or lose market share. The only vehicle that probably won't have a rebate will be the Turbo version of the PT Cruiser. Rick
  • Howdy,

    Just found this reference article on TheCarConnection:

    Looks like we will know by the end of the week.

    All the best,


  • Anyone here have a new 2003 QC yet? I'm looking at buying a 2003 QC SLT Plus 4x2 with the 4.7/auto. Several dealers are offering below invoice deals and I can't decide between this or the Ram 1500 QC.
  • Where are Dakotas manufactured? Is there 1 plant or multiple? I just ordered a Quad and the dealer siad he didn't know where they are made.


  • bpeeblesbpeebles Posts: 4,085
    I beleive that my 2000 Dak has a sticker that claims "Built in Dodge City"

    (cant verify it right now.... wife took my Dak to work this morning)

    I know that some Daks are built in Brizal (CampoLargo) cturing/chrysler-mfg-campo-02.htm

    Of course the 4.7L engine is built in the newly-renovated, Mack Avenue Engine plant
  • dustykdustyk Posts: 2,926
    Dakota -- Warren, MI
    Durango -- Newark, Del
    RAM -- Warren, MI
    RAM -- Lago Alberto, Mex
    RAM -- Saltitlo, Mex
    RAM QC -- -- --St. Louis North
  • mopar67mopar67 Posts: 728
    Are you sure about Lago Alberto? I understand it was closed as part of the restructuring?
  • dustykdustyk Posts: 2,926

    Well, I have the list I downloaded from the Automotive News website back in October. It should be fairly current. But you may be correct.

  • I conclude it must be Warren, MI. Now, if I could just figure out how that rail ships to the Bay Area.

    Thanks for all your help,

  • bookittybookitty Posts: 1,303
    Anthony, thank you for the link previewing the 2005 Dakota. Awesome! Now for a 5.7 Hemi, 6 speed manual and a Cummins Diesel option.

This discussion has been closed.