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Dodge Dakota Performance and Towing Mods

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Comments

  • sunburnsunburn Posts: 319
    Dusty,

    That's an interesting distribution on your gas mileage. Very one sided. Come to think about it, mine's probably similar, just about 4-5 MPG less. But, my QC is a 4x4 with 3.92 gears.

    The one thing I've noticed with the newer Dakotas is the mileage ratings are much higher than mine. My 02, 4.7, auto, 4x4 was rated at 13/18. An 07, 4.7, auto, 4x4 I recently saw was rated at 15/20. I know the newer Daks have a 5 sp automatic, versus my 4 sp. But when that was introduced, the highway mileage only went up by 1 MPG. I wonder what else they changed to get the better mileage?
  • sunburnsunburn Posts: 319
    I recently read where the SAE is coming up with a set of standardized test to determine tow ratings. This will hopefully level the "tow ratings" playing field.
  • bowdinbowdin Posts: 11
    Most people here seem to agree with DC: tow with overdrive off in hilly conditions. Some people have warned about overheating the torque converter if you tow in overdrive.

    But what about the lockup system? If I run at ~70mph, I'm spinning about 2500rpm (2002 Quad Cab, 4.7L, 3.92 rear end). Give it a little gas, it spins up to about 3100rpm, I assume this is the torque converter unlocking?? Give it more gas, it shifts into 3rd (3500rpm to maintain about 70mph).

    So is the danger of towing in overdrive that it unlocks and locks too much? If it stays locked is it bad to tow in overdrive? Thanks for any input.

    -Eric
  • sunburnsunburn Posts: 319
    Yes, the locking and unlocking of the torque converter is one cause of transmission overheating. But, you have to be careful when towing in OD. I used to do it when towing a 2500 lb pop-up camper. I did have any problems, except when my speed dropped under 50 MPH.

    Now that I've moved up to a 4500 lb travel trailer, towing in OD is out of the question. The reason is the load is great enough, the transmission won't shift into OD, except when going down hill. When the OD is on, the torque converter will not lock up in 3rd gear, hence a lot of heat is generated due to the torque converter slippage. When the OD is off, the torque converter will lock up in both 2nd and 3rd gears.

    It just depends on how much you are towing.
  • bowdinbowdin Posts: 11
    Thanks for the reply. I'm towing 4200lbs. Overall the 4.7L, 3.92 rear does fine, and in overdrive it will shift into 4th and even drop down to 2500 rpm at 70mph in many situations (even a slight upward grade). Is this hard on the torque converter or tranny? Obviously I'm not totally versed on torque converter lockup and what the issues are.

    The manual says "overdrive off in hilly conditions." But the definition of hilly depends on whether you live in Kansas or Colorado. So (in marginal situations) is there a transmission behavior to look for to indicate when to turn overdrive off?
    -Eric
  • sunburnsunburn Posts: 319
    Considering that the later model 545RFE transmissions (the 5 speed version of the 4-speed 45RFE. The two transmissions are mechanically identical) just have a "tow/haul" mode, you can't lock out the OD, so it would seem to be okay to tow in OD as long the transmission isn't shifting excessively or the torque converter is unlocking and locking excessively. Manufacturers tend to be either vague or very restrictive (i.e. "don't") when it comes to towing in OD.
  • bpeeblesbpeebles Posts: 4,085
    When I purchased my Dak, I orderd the manual xmission from the factory. I never have any issues with the torque converter - LOL

    Besides, ordering direct from the factory is CHEAPER than purchasing off the dealers lot and I got the options I wanted. This is because the dealer has a GUARANTEED sell when you order from the factory. The dealer's purchaser purposefully orders cars for the lot which have options with the highest markup. This be because they still have to SELL the vehicle. (And brush the snow off of it all winter!)
  • dustykdustyk Posts: 2,926
    Sunburn,

    The first one or two years of the 4.7 in a Dakota they used a 47 or 48mm throttlebody. In 2002 or 2003 that was increased to a 50mm.

    The camshafts are different for each year up to 2003. The 2003/2004 camshaft duration was changed to 243.5 degrees intake, 253.7 exhaust. I think that fuel delivery and timing algorithm changes permitted a decrease to valve overlap (17 degrees) for an increase in low end torque and improved idle. Likewise since '04 they've changed camshaft profile and fuel delivery some more.

    The mere fact that the 545RFE transmission has five normal forward gear ratios and considerably less parasitic losses than the previous "RE" series transmissions could explain part of that 1 MPG difference. Top gear ratio for the 46RE is .69, and .67 for the 545RFE. Pretty close but a slight advantage for Dodge's newer automatic. The intermediate second gear on the 545RFE might actually contribute more to better gas mileage.

    Starting in 2007, Chrysler is phasing in Variable Line Pressure (VLP) to its automatic transmissions. This will significantly reduce parasitic losses. In think the RFE will get VLP in 2008.

    On my son's last leave I rented him an '05 Dakota Quad Cab, 4x4. It had the same axle ratio as yours. He was able to average 16.6 for the two weeks he had it in very mixed driving.

    Best regards,
    Dusty
  • dustykdustyk Posts: 2,926
    The 45RFE and 545RFE are nearly identical with the exception of servo operation. They both have three planetary gear sets, but the 545RFE allows the use of six forward speeds. On Jeeps at least, I'm under the belief that the 45RFE Transmission Control Module (TCM) can be reflashed to make it operate like a 545RFE.

    Regards,
    Dusty
  • Looking at adding a chip, air intake and upgrade exhaust all to gain more towing muscle.

    Is the result worth it and what are the most reliable products?
  • bpeeblesbpeebles Posts: 4,085
    Most reliable exhaust system is HANDS-DOWN the Borla with their famous "Million Mile Warantee".

    For me, A Borla exhaust was the only way to go. Here in Vermont, most exhaust systems last about 3 winters. Since I expect to keep my Dak over 12 years, I installed a Borla the first year I owned it. It still shines like the spoons in the kitchen drawer!
  • i have an 08 dakota with the factory tow pakage, i purchased an electric brake controller and harness that is supposed to plug right into the truck somewhere according to the controller mfg. my local dodge dealer says there is no such plug and they would be happy to do the wiring for a charge. im not buying dodges story but ive spent 2 hours under the dash and still cant find this plug. can anyone help me out with this? please!
  • i have a 2002 Dak with a 4.7, quad cab, 2wd, auto trans with 3.55 gears and 9.25 rear .it has a few mods to it nothing fancy i have a K&N cold air, and flowmaster 40 series cat back single in dual out. my question is this... we have a 23ft four winns runabout boat that weighs about 3,760lbs. (i have pulled it several times but only for a short distance but it is up quite a steep hill in ky) is there anything i can do to the rig to help it out a little to add a bit more torque? i have no tow package from factory but do have a class III hitch, i am looking at tranny coolers but dont really know which way to go, also looking at a computer chip that has different power/millage settings.

    thanks
    B
  • bowdinbowdin Posts: 11
    I have an 02 with the tow package. The plug was under the dashboard, to the right of the steering column. The mfr of the brake controller should be able to tell you where the plug is on an 08 Dak. Good luck.
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