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  1. #1

    Default 1500 HD heating up towing up mountains

    I would like some advice on that RPM produces the best hill climbing results while towing my 26FT 5th wheel travel trailer(about 6200#). I try and accelerate on the flats to get a good running start on the incline but sometimes the truck starts to slow down and gets very hot, to the top of the engine and tranny gaues. Should towing be done near the top of the torque range on hills and what should that be? Thanks, and good day, Henry.
    07 2500HD Duramax , 4DR and 26 Prowler 5th wheel Travel trailer, 57 Chev wagon with 14' Bonair travel trailer, and 71 Nova. Canadian Regional Coordinator

  2. #2


    If you tow in overdrive what happens is the torque converter has to stay unlocked because your foot is burried to the floor. Driving in Overdrive without lock up <which is what you are doing> overheats the transmission. Once this happens the fluid will vent out and can possibly start a fire under your rig!
    So never tow in overdrive unless you have enough engine power to keep the torque converter locked up. You can usually tell if the converter is locked by watching your tach.
    Best bet is to pull the selector down into the drive position when climbing hills.

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  3. #3
    Legend cascott325's Avatar
    Join Date
    Aug 2008
    Lawrenceburg, Kentucky


    i think that you are right, towing should be done at higher rmp's. when you are in low rpm range, your motor bogs down and has to work harder to get the job done, where in the higher rpm range, it its still working hard, but you have a better fuel air ratio creating more torque and horses. maybe someone can put it into technical terms, but its why the tow/haul option extends the shift range to higher rpm's when active
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  4. #4


    I would suggest checking the cooling system and make sure everything is working correctly. I've seen similar symptoms from a weak fan clutch. Fan clutches tend to fade over the years, it's possible that at this point your fan can no longer draw enough air through the radiator to keep up with that kind of engine load. I would also suggest checking the radiator for blockage (internal and external) to make sure coolant and air can flow freely through.
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  5. #5


    Just to add to my story, the coolant temp drops rapidly when I crest the hill and will maintain the temp below 1/2 gauge. I guess the cost of a system flush would alleviate one concern. I had a clutch fan go on my motorhome on the way to vend at an auto flea market and had brought a few used clutch fans along with me to sell and replaced it while we were there. The bad clutch had no resistance to it, Henry.

  6. #6
    Sr. Mechanic John W's Avatar
    Join Date
    Sep 2007
    St Peters, Nova Scotia, Canada


    I tow a 28ft Golden Falcon with my Silverado Z71. 5.3 four speed auto with tow haul. I always tow in #3 and tow haul activated. No problems so far and the Cabot Trail has some fair sized hills.
    2000 4x4 Ext. cab 5.3 Z71
    2009 Corolla

  7. #7


    If the engine temp. continues to get too high, you could try some water-wetter. Haven't seen it around in a while, but I used to be able to get it at the local Wally-world.


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  8. #8
    Master Mechanic daddytech's Avatar
    Join Date
    Mar 2008
    Portland TN


    I agree with the others you can't tow in OD specially not on the hills. it'll burn that transmission up quick doing that. Our 2000 AWD astro van allows us to cheat a little that way it has a Tow Haul button and it uses the OD on the long flat runs but as soon as an incline starts it locks in the regular gear (my interpretation of what happens) and then i'm good again till i hit another down hill slope or flat run.

    My tahoe however I have to tow in 3 and it shifts a little hard on the inclines still but on the open flat out runs i pop it into OD and let it roll. I no longer have problems with mine over heating or feeling like it's shifting so hard that it feels like the transmission is coming out from under the truck any more. and it doesn't over heat on those kind of trips any longer either.

  9. #9
    Sr. Apprentice fx2offroad's Avatar
    Join Date
    Oct 2008
    Yukon, Oklahoma


    Yea, don't ever tow in OD unless your on flat road and your rig isn't shifting in and out of OD. It can burn up your transmission. It is also good for lifted vehicles to drive with OD off if you going up and down hills, Because your rig thinks it's towing something when you throw 37's on it.
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