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Thread: 5 to 6 speed conversion????

  1. #1
    Join Date
    Mar 2001
    Location
    williamsburg, ohio ,usa
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    340

    Default 5 to 6 speed conversion????

    Just back from trip to Florida tow show. 18.4 MPG over 2300 miles, about 8000#, mostly 68 to 74 MPH some up to 80 MPH. What could I expect with a 6th gear???? half, 3/4, 1 MPG better???? Those who have enabled the sixth gear care to chime in, Thank you! Is it worth the expense? What is the least expensive way to enable the sixth gear? (04.5 LLY) How strong is the sixth gear, for trailer pulling, can it be locked out so fifth is top gear when pulling a heavy trailer? Thank you. bob.........................
    Bob O.
    2004 K2500 DA LLY CC LT LB Wow! Edge w/A + BS + CAT pre fuel filter, 06 air box,
    2002 C6500 EC. 7.2 Cat NoMar rollback/ 92 C7500, 7.2 Cat, 25ton No-Mar / 2005 C5500 D/A rollback / 1969 Corvette 350-350 4spd AC T-top stock orginal
    XP850LE WOW nice ATV, 09-550XP hers, 03-Predator, 04 Honda400EX, 05-Banshee, 08-KTM525, 08 KFX700, 38' enclosed GN hitch

  2. #2
    Join Date
    Mar 2000
    Location
    Loyal WI US
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    10,792

    Default

    Quote Originally Posted by carco View Post
    Just back from trip to Florida tow show. 18.4 MPG over 2300 miles, about 8000#, mostly 68 to 74 MPH some up to 80 MPH. What could I expect with a 6th gear???? half, 3/4, 1 MPG better???? Those who have enabled the sixth gear care to chime in, Thank you! Is it worth the expense? What is the least expensive way to enable the sixth gear? (04.5 LLY) How strong is the sixth gear, for trailer pulling, can it be locked out so fifth is top gear when pulling a heavy trailer? Thank you. bob.........................

    In my opinion/experience, the wind is the biggest factor. Slow down and save. I have the 6 speed kit on my 2005 and love it. We sell them on our web site. I haven't really seen any solid MPG gain. The big key is the lower RPM reduces engine noise significantly at highway speeds.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

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  3. #3
    Join Date
    Mar 2001
    Location
    williamsburg, ohio ,usa
    Posts
    340

    Default

    John, thanks for the reply. Yes, wind resistance is a big factor as well as RPM over about 2000rpm, which also increases speed thus wind resistance, wow can't win! Sounds like a lot of money for little to no gain, reading between the lines of your response John?? Thanks bob..........
    Bob O.
    2004 K2500 DA LLY CC LT LB Wow! Edge w/A + BS + CAT pre fuel filter, 06 air box,
    2002 C6500 EC. 7.2 Cat NoMar rollback/ 92 C7500, 7.2 Cat, 25ton No-Mar / 2005 C5500 D/A rollback / 1969 Corvette 350-350 4spd AC T-top stock orginal
    XP850LE WOW nice ATV, 09-550XP hers, 03-Predator, 04 Honda400EX, 05-Banshee, 08-KTM525, 08 KFX700, 38' enclosed GN hitch

  4. #4
    Join Date
    Mar 2000
    Location
    Loyal WI US
    Posts
    10,792

    Default

    My best advice is if you do it, do it for reasons OTHER than MPG gains and you will not be disappointed.
    Kennedy Diesel-owner
    More than just a salesman-I use and test the products that I sell on a daily basis!
    Superflow Lie Detector in house
    2002 Chev K2500HD D/A CC Long LT 11.77@ 124mph at 7700# fuel only-e.t. needs help
    2005 Chev K3500SRW D/A CC Long LT(SOLD)
    2007 Chev K2500 Classic EC Short LT (Sold)
    2012 GMC K3500SRW D/A CC Long LTZ Happy Birthday to me! Built 1 working day after my birthday and delivered 7 days later.
    2016 GMC K3500SRW D/A CC short LTZ

    Custom tuning in house using EFI Live tuning software!

  5. #5
    Join Date
    Apr 2001
    Location
    Alvin, TX, USA
    Posts
    192

    Default

    John
    How much does the 6th gear reduce the RPM? I just returned from a a 3000 mile round trip to CA from TX towing a large road bike on a utility trailer with my 05 LLY. Averaged 15 mpg over whole trip running 70 mph and it was windy for the majority of the trip. Noticed whenever I slowed to 65 mph or 200 RPM, mileage increased significantly. Granted, wind resistance is less at 65 but the lesser RPM contributes as well.

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