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Towing in overdrive

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  • Towing in overdrive

    I noticed in another thread several posts advising to never tow in overdrive. I know it's been covered before but if we could just clarify:I been led to believe that:* The OD gear is a mechanical link to the engine, vs a hydraulic link in the lower gears, and therefore easier on the tranny and the fluid.* Shifting is what builds heat and * as long as the car shifts into OD & stays there, towing in OD is better for the trans than towing in Drive.In town, in heavy highway traffic, and in hilly country I always turn OD off, but I ordinarily cruise in overdrive.Agree? Disagree?thanks,jtw
    It's all about the tools.

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  • #2
    Re: Towing in overdrive

    Just my opinion here, but the manual on my 1994 K1500 says to not use OD while towing. Fast foward 11 years and 142,000 miles and the original transmission is still with me and going strong [knock on wood].I don't have the mechanical expertise to know whether it would be OK to use OD. I simply do what the book says and it has so far worked out. How's that for a non-answer?

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    • #3
      Re: Towing in overdrive

      Follow manufacturers guidelines. That being said, I tow in OD as long as the tranny isn't shifting in and out alot. In stop and go traffic OD is off.

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      • #4
        Re: Towing in overdrive

        jtexas, I agree with you. 142,000 on an auto that tows is very good, so you must be doing it right. We won't even get into gear ratios, RPM's, speed limits, terrain, etc.
        Lake Shasta with Mt. Shasta in the background, June 2011

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        • #5
          Re: Towing in overdrive

          Good point, JTex.In some (not all) automatic OD transmissions the converter is locked in OD. On others it may lock in any gear or only the top 2 or 3 gears. You are correct that IF you have this transmission the tranny runs cooler when the converter is locked. These vehicle manuals usually don't tell you not to tow in OD.Then there is torque loading the engine at less than peak-torque RPM. That can be bad for the engine with a heavy tow. If you are anywhere near the tow rating lock it out.With manual trannys the OD gear ratio assumes highway speed with no tow. Towing anything near the rating will overload the drive train and engine in OD. Mfgs almost always say don't tow with a manual tranny in OD.Good luck.
          sigpic

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          • #6
            Re: Towing in overdrive

            I was told by a mach. that even if you are OD and it is not shifting you still should take it out. He said that the plates and gears are still slipping and causing damage just not enough slip to shift out of OD. I had a friend who toad alot and had to replace trans. @ 80,000 and they said it was because he used OD while towing @ high speed even though he did shut OD off in ctiy driveing. I fill pay extra in gas and take out of OD and save the trans

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            • #7
              Re: Towing in overdrive

              SCS - if the mechanic you talked to said gears and plates are slipping in OD, don't let him near your tranny. There is considerable misinformation here. The only time an automatic transmission slips is during the shifting process. All other times slippage only goes on in the torque converter (just like it does when you sit at a stop lite) and even that is eliminated when the converter locks up. Nearly every automatic transmission already has a cooler built into the radiator and its there to make sure the fluid stays at a uniform temperature -- in northern climates you can overcool. Addition of an external cooler is only required if you are pulling extremely heavy loads with lots of starting and stopping and/or city/hilly terrain where shifting has to occur. Towing in or out of overdrive depends on a number of factors and is not a "must always" situation. The most important is knowing what the axle ratio is and secondly what load you are towing and how the transmission behaves. Towing too heavy a load with too low an axle ratio causes frequent shifting and can cause engine overheating whether or not OD is used. There are simply too many mismatched tow vehicles out there. That's why various ratios are offered. Deeper gears (higher ratios) are better for towning -- period. For those that are math challenged 3.0:1 is a lower numerical ratio than 4.1:1 so don't confuse low ratio with lower gear. If the transmission does not hunt (repeatedly downshift or require the converter to repeatedly lock & unlock) it is ok to tow in overdrive assuming engine temperatures stay normal. Even if the converter unlocks periodically that's not a problem so long as its not unlocked for a prolonged period. Few people can tell when this happens unless they have a tach and even then they often mistake that action as a transmission shift. Overdrive shifts result in approximately 18% RPM change whereas a torque converter unlock will see about 800 RPM change. You can check this by maintaining a steady speed (55 - 60 MPH) and then just barely touch the brake pedal. You will see the tach rise as the converter unlocks. There is absolutely no difference in towing in overdrive than there would be towing in fifth overdrive or fourth direct in a standard transmission. Nothing is slipping except as pointed out above and that's what the tranny is designed to do. At age 65 I've probably logged more tow miles than most folks on this board and I've never lost a tranny -- but the key is know when its ok to tow in OD and when its not. I routinely run all of my tow vehicles in excess of 100,000 miles and never have a problem (all GM if that matters).

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              • #8
                Re: Towing in overdrive

                Upinsmoke, Good Job explaining it.
                Lake Shasta with Mt. Shasta in the background, June 2011

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                • #9
                  Re: Towing in overdrive

                  Yes thanks, I have a 03 F150 with OD and have been locking it out when "when I remember" must of my towing is on the freeway and level so not much shifting going on. RPM are much lower and the motor is not lugging so I don't worrie too much about OD or no OD.

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                  • #10
                    Re: Towing in overdrive

                    Did one 50 mile trip w/ OD on the Mountaineer w/ trailer. Actually lost 0.7 MPG as without OD. Hated the accel on mild grades too.

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                    • #11
                      Re: Towing in overdrive

                      Follow your owner's manual. In my "modern" (newer than say, 1994) cars, it specifically says to tow in OD. My belief is that these are computer operated transmissions and are best served by putting the tranny in OD and letting the computer decide when to shift. My older (86) chevy P/U, I believe says to tow in drive (or 3rd?), not OD. My newest Suburban has a "tow/haul" switch which makes everything very easy! (if I remember to use it). It changes the shift points and also makes the shifts more abrupt/hard. Keeps the revs up and avoids much of the slippage in the smoother, normal shifting.

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                      • #12
                        Re: Towing in overdrive

                        My vehicle's manual advises to disable overdrive while towing. Now if I were towing a couple thousand pounds on level ground I might decide to ignore this advice. Since I am towing at the limit of my rated towing capacity (7,000 lb), I disable overdrive for towing.I suggest following the advice in the tow vehicle owner's manual.
                        Ron

                        2000 Camano Troll
                        North Charleston, SC

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                        • #13
                          Re: Towing in overdrive

                          The key to OD or not OD is to know what your vehicle is doing. If the torque converter continually unlocks and locks, or the tranny shifts from OD to D frequently, those are signs you better pop it into D.

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                          • #14
                            Re: Towing in overdrive

                            I tow in O/D in my 97 Mountianeer 5.0 AWD with no problems. But I probably tow a much smaller boat than most of you folks. In the Mountianeer, you hardly notice the 1200lbs behind you. I am very aware of the shifting and locking behaviour of that trans and it seems to not be affected by the trailer. I just accelerate slowly, and let the truck make its own shift decisions. On long trips I find my speed creaps up to 70 - 75 before I catch myself and coast back down to 60 - 65. I do think it uses more gas towing but I have not checked. We have 150K plus miles on that truck. Its a truly great machine.
                            sigpic 1985 Bayliner 1600 Capri Cuddy, 1965 MFG Niagara Custom. >> MFG Video<<. >> MFG Project<< >>Bayliner Hard Top Project<< >>Bayliner Repower Project<<

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                            • #15
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                              Re: Towing in overdrive

                              Give this a try next time you tow. Find a long flat stretch and set your cruise control at 55 with your tranny in OD. Now put your foot lightly on the accelerator. Now shut off the OD. You will find the accelerator actually backs off just a little even though you're still running 55. Less pedal...better economy.'96 F150 351W 3.55 rear E4OD tranny pulling Monterey 256 8080 lbs

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