Am I Doing it Wrong?

Discussion in 'Towing & Transportation' started by lone_star_dsl, Jul 24, 2012.

  1. lone_star_dsl

    lone_star_dsl Full Access Member

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    I am not new to trailer towing, far from it actually. I have a class A CDL with over 200,000 miles under my belt. My trucks towing ability, or lack thereof, has me wondering if I've been doing it wrong.

    With my fifth wheel, my GCW is around 16,000 pounds yet my truck seems to always struggle with it. It doesn't struggle in the suspension or the ride but it seems like I'm down on horsepower compared to other 99+ 7.3L trucks. As an example, I was heading up I 25 from Denver to Fort Collins. While there's no major hills on this section of road there are a few areas in which I have to take my truck out of overdrive. In doing so, I bring the revs up to 2500 and bring my speed down the 65 mph. While I was chugging along I noticed a truck very similar to mine pulling a much larger fifth wheel coming up beside me. While the truck wasn't at light speed, he was definitely in the 70 – 75 mph range.

    Just as the truck got my side I looked over and noticed a couple with the combined age of nearly 300 years. The truck had no gauges and from my vantage point, appeared perfectly stock.

    As I let the truck move over in front of me I put the hammer down in an attempt to keep up with him. While I typically don't like letting my truck rev over 2500, I brought it up to 3000 just to see what would happen. Even at 3000 RPM, the old man and his Ford walked away from me.

    While I know I have a slight leak in my up pipes, would this rob me of enough power to keep up with the heavier rig?

    I am very pleased with my DP Tuner and its abilities to keep my EGT's manageable. There have only been a few times when I've had to come off the throttle to keep them in check. Usually this is only because I'm driving into a stiff headwind.

    My truck has spent the last few years as the tow rig for my excavating company as well as being the family truckster towing the fifth wheel for our vacations. Are there any modifications that won't break the bank or require a complete engine rebuild that would make my truck a tow monster? I'm not talking about being able to tow 50,000 pounds at 100 mph but rather being able to tow a fifth wheel that weighs around 10,000 pounds without having to kick out of overdrive at every overpass.
     
  2. BIG JOE

    BIG JOE Full Access Member

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    A Slight up-pipe leak.. is a Leak, you might be losing some boost that would be available.. if it wasn't leaking ?

    R&R the fuel pump inlet fitting yet ? In-tank fittings too ? Air in the fuel is an enemy.. to power.

    Fuel pressure stock ? Maybe bump it up to 70 psi ?

    HX mod to equalize oil pressure to the injectors ?

    203* thermostat ? These PSD's run better.. a Tad warmer.

    The 315's maybe ?

    Jus' fer starters :dunno

    Joe

    OBTW...Thoze 'ol geezers wern't me & the wife.. our combined age is only 132 :D:sly:lmao
     
    Last edited: Jul 24, 2012
  3. lone_star_dsl

    lone_star_dsl Full Access Member

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    I was hoping you would have an opinion on this, Joe.

    I haven't done any of those things you mentioned except getting rid of the 315's (need to update sig), pull every bit of lift off the truck and actually lower it another inch. I am now running 285's.

    With everything you have done to your truck, can you haul that tall and heavy trailer down the road without kicking out of overdrive on every little hill? If so, it appears that I have a good blueprint to start with.

    BTW, my trailer is a mid profile 24 footer with a gross weight of only 7,000 lbs. It's not the tallest or heaviest but it sure feels like it.
     
  4. BIG JOE

    BIG JOE Full Access Member

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    I gross out at 18,800, I very seldom need to downshift, unless pulling an actual grade or hill, but, mine is a ZF 6 speed... that makes a diff... Kinda hard to compare a Manual against an Auto ?

    Yer call but I wouldn't worry about 2500 rpm that much, Man or Auto. These 7.3s are making good power @ 2450... that's where the Torque, and HP curves cross.

    With 3:73s, @ 1850 rpm (w/235s) the Torque is doing the grunt work, @ steady speeds. Above 2000, the PCM (and Chip/tuner) does it's whizo stuff.. and yer kicking in the HP via fuel mapping. Above 2500, the turbo boost pressure (enter: your up-pipe leak ?) is adding to all of that.

    I've never owned a Diesel with an Automatic.. so I'm not experienced enough with that, to offer many driving/towing tips or technique.. but if you fix that up-pipe leak.. do the few tweaks I've mentioned (under $200 BTW).. Keep yer RPMs above 2200 when pulling hard.. I'd betcha you'd do much better, towing. Cruise'n too.

    Everything in my Sig. was done for towing our 5r.

    Joe

    If you deside to do any of these Mods.. Post up, or PM me.
     
    Last edited: Jul 25, 2012
  5. BJS

    BJS Full Access Member

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    how are your trans temps doing? where are they when running empty & with the trailer?

    the rubber used in the seals in transmissions get old and start to get brittle especially if the trans has gotten a bit too hot.
     
    Last edited: Jul 30, 2012
  6. lone_star_dsl

    lone_star_dsl Full Access Member

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    I see about 180 around town and 190-200 while towing. The hottest I have set on my CTS is 209.

    I've been wondering about my trans for a while. It's dead stock with nearly 200k on it with the last 15k with a DP Tuner. My last dyno run shows the truck not putting power to the wheels and I'm thinking the trans is the culprit. My last dyno was 255 hp stock and only 288 on the 80 hp setting.

    I haven't noticed any slipping but I think the TC is swallowing power.
     
  7. BJS

    BJS Full Access Member

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    You went were I was heading in that the transmission is sucking a bit more of your power than you'd like. however ensure that the up-pipe leaks are fixed to make sure the transmission is getting the power. Are you getting any haze out of the tailpipe?
     
  8. lone_star_dsl

    lone_star_dsl Full Access Member

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    It's a little smokey until the boost comes up but I rarely get any haze at highway speeds unless it's lugging down while climbing a hill.
     

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