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  • Disappointed in towing

    I traded in my wife's 08 Tahoe 5.3 motor with 100k miles for a 12 gmc Yukon 5.3 l with 15k miles. I towed my 02 xstar yesterday for the first time yesterday. The tow includes a large climb over parleys summit. This gmc would not down shift the way my 08 Tahoe did. I was in tow/haul mode and had the gas pedal down all the way and the down shift took forever. I could do 65 or so up and over the summit in my 08 and I was struggling to be at 50 in the gmc due to the fact it didn't down shift to keep the speed consistent. What am I missing

  • #2
    Different rear end. When they went to the 6 speed they also put substantially higher gears in the rear ends for the sake of economy.
    sigpic

    1997 Prostar 190, TBI 350, 1:1, OJ XMP 13 x 11.5, Stargazer, Hot Shower, Heated Drivers Seat, Reuben/Mountain Rock/Nite Navy


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    • #3
      Yep the solution is too find a 3.73 to go with the 6 speed like what was probably in your 08 with a 4 speed. I think the 6 speed uses a 3.08 or 3.23. Also, you can tow in 5th gear to help
      1981 MasterCraft
      19' Skier 351W PowerSlot
      Long gone is the Trans AM waiting for another

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      • #4
        Your GMC is under warranty. Take it in and have it checked out. Even with a higher rear differential ratio the lower ratios of the first 4 sets of the 6 speed auto give you a better low end final drive ratio for towing. The sixth gear set is to give the extra miles per gallon rating on highway and all six allows for additional city MPG as under normal driving shifts come quicker reducing rpm. Results help raise the all important CAFE rating. At first glance your issue sounds like a programming issue or a speed sensor.

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        • #5
          Something is going on. The 4 speed and 6 speed have similar ratios in the 3/4/5 gear range. Definitely have it looked at.

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          • #6
            Is there an OD button and was it turned off?
            What does the fox say?

            Ring-ding-ding-ding-dingeringeding...

            You know they all have a little string hanging out, but it's not a tampon, it's a price tag...

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            • #7
              Some times you can look into a .. Super chips, or bully dog system.. to reprogram your truck and in tow modes change shift points

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              • #8
                Something is wrong...

                I towed my last boat from Florida to Michigan with a 5.3 Tahoe with a 6 spd, and through the mountain of Kentucky/Tennessee the trans was shifting into 4th to maintain 75 mph.

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                • #9
                  tow/haul generally limits shifting, but that sounds extreme. The different rear end would explain more frequent downshifts, not what he describes.

                  Either your tranny is not programmed correctly, or perhaps that particular model has a real slow downshift mode in tow/haul.

                  You can always manually drop it down, yes?

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                  • #10
                    through the mountain of Kentucky/Tennessee the trans was shifting into 4th to maintain 75 mph.
                    Why would you stress your Tahoe to maintain 75 mph uphill? You must have had it floored; seems like you're flogging it a little. Not to mention that ST tires are rated to 65 mph.

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                    • #11
                      Originally posted by Miss Rita View Post
                      Why would you stress your Tahoe to maintain 75 mph uphill? You must have had it floored; seems like you're flogging it a little. Not to mention that ST tires are rated to 65 mph.
                      It's not a stress for a Tahoe to maintain that speed and it would not need to be floored. That is why vehicles that can tow have a GVWR that you don't exceed. Also, what are ST tires? The stock tires on a Tahoe have a speed rating of at least 98 MPH. If not, the fuel shut off MPH would be lower.

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                      • #12
                        ST refers to the trailer tires, not the truck....FYI...

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                        • #13
                          If you're pulling a boat uphill at 75 mph the throttle would have to be wide open, or close to that. Personally I don't see a need to push it that hard. It doesn't make any difference to me if I get to the top of the hill 30 seconds sooner. Also, there's a lot of weight there. The Tahoe weighs 6000 lbs, your boat may weigh 4000-6000 lbs, then add people and gear. If something happens at 75+ mph (blowout, deer crossing the road, stupid drivers) it won't be pretty. Fuel consumption is also an issue. Just because you can pull the boat that fast doesn't mean you should.

                          I know there are a lot of people who routinely tow at 75-80 mph who "never had a problem". To each their own.

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                          • #14
                            Stopping distance and control at that speed is going to be very poor, especially with a light duty truck. I never tow over 65, though my ecoboost could pull much faster with ease. It's the stopping/control if something goes wrong that is the concern. And as mentioned, your tires are not rated for that speed.

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                            • #15
                              Safety first.
                              For comparison I have 2 Silverado's. One is a 2001 2500 2wd standard cab 8ft bed 6.0. My personal truck is a 2005 1500 crew cab 6ft bed 4wd with the same 6.0 engine.
                              Up a steep grade my older 2500 will pull up a hill with 3/4 throttle and maintain 80mph if I wanted to. Surpass it with ease if at full throttle. Where as my newer 1500 with the same engine and it being longer on the same steep long incline would be maxed out full throttle to maintain 70-75mph.

                              There is a huge difference between a light truck and heavy duty truck. Even with the same engines. As mentioned safety should be first. My 2500 tows a 4000# trailer every single day. My 1500 would get chewed up if I tried to do that. My brakes would be replaced monthly, my truck would deteriorate extremely fast. etc etc.

                              My personal truck is sufficient to tow it. And prettier so I do. So just know your limits. Your truck is fine and there is no need to go that fast in a truck not equipped to do so.
                              sigpic
                              When I was a child, I used to talk as a child, think as a child, reason as a child; when I became a man, I put aside childish things.
                              1 Corinthians Chapter 13 - 11

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