Some info on an '07 Ram 1500

Discussion in '4x4's, SUV's and P/U Trucks' started by Taliesin, Dec 9, 2008.

  1. Taliesin

    Taliesin Well-Known Member

    I hadn't driven my big truck for quite a while and decided to drive it during the long Thanksgiving weekend. Not for very long, and only because I couldn't fit my wargaming miniatures in the cab of the Ranger.

    Some interesting information comes to light with my new skills/alertness/experience from this site:

    With the tires pressed up to max sidewall this thing coasts for a VERY long time, much longer than the Ranger does.
    On my route home I have a series of hills that I drive over. With the Ranger I get to 55 at the bottom of the first hill, then coast the rest of the way home (about half a mile). With the Ram I only need 50 mph. At the top of the second hill the Ranger would be at 45, and the Ram at 35, but getting to the next intersection is all downhill and both trucks are at 35 there. I still have a lot of work to do in knowing what speed to get up to so that I don't use the brakes at my drive, but the Ram gets there at 27 mph and the Ranger at 25.
    If I drove this often, I think I could break the highway EPA (gas fuel) while using E85!
    The new/old EPA stadards are (city/hwy/cmb): new gas: 13/17/14, old gas: 14/19/16, new E85: 8/12/10, old E85: 9/13/11. Heck, pre-hypermiling I matched the new EPA combined while towing with E85.

    57 mph is only 1500 rpm. I know there are people here that would kill for that to gearing.
    However, it is difficult to get it to lock into 5th gear for DWL. On the up side of that, 4th gear is still something people on here would kill for: 55 mph at 1700 rpm.
    Unfortunately 3rd gear runs around 2K rpm for 50 mph, and anytime I go from N to D if automatically chooses 3rd to start with. It will switch to 4th pretty quickly after that, but I hate that time in 3rd.

    I think I can, with some more work, keep it below 2K rpm for the bottom 4 gears and 1500 for 5th.
    I almost wish I drove it more often, but I don't think I can match the ~30 mpg I am getting out of the Ranger yet.
    It's not a vehicle I drive often, and was bought for a specific purpose. However, I think it could be hypermiled very effectively (only when looking at & of EPA).
    I could only wish that many other vehicles had designs that could be hypermiled as effectively. I think this truck could easily get double EPA with a SG and P&G, though Pulsing in 5th gear really isn't possible.
     
    Last edited: Dec 10, 2008
  2. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    I think you may be out of luck getting from N back to D without it engaging in third gear. My guess is that is normal behavior based on the fact that transmissions are programmed to lock out overdrive gear(s) unless the converter is locked. And the converter won't lock until a few seconds after the computer decides that the TPS, engine load and road speed allow it to happen. Once the pressure switch in the TCC signal passage closes (meaning the converter is locked), then 4th and 5th become available and upshifts will occur.

    5th is likely so tall that any serious P&G will bump it out of top gear with a forced downshift. Wayne found the same behavior in a Saturn Aura 6-speed AT a few months ago during a week of driving, noting it wouldn't grab 6th until near highway speeds, and even then it was very quick to downshift. Most AT's with 5 or more forward speeds have a very tall overdrive and so the slightest bump of the throttle or increase in engine load will prompt a downshift. On a pickup truck, even a prolonged gust of headwind can be enough to knock it out of 5th. The only solution is continued gentle throttle action and time taken for the transmission controller to learn the new gentle driving method.
     
  3. Taliesin

    Taliesin Well-Known Member

    One thing I learned early is that 4th gear is still an Overdrive gear, so going to 3rd when switching from N to D makes sense.

    Also, the RPMs I noted might be more informational if I mention that the tach goes up to 7K and shows no redline.
     
  4. MaxxMPG

    MaxxMPG Hasta Lavista AAA-Vee Von't Be Bach

    The Ram pickup uses pushrod OHV engines, so redline is probably at or just below 6000rpm. They don't usually show the redline on the tach in an AT-only vehicle because the computer cuts the fuel supply before the revs can reach the danger zone. On modern cars, the redline is shown on the tach for marketing purposes only - you'll never get into it except on a MT vehicle that you choose to shift to 1st or 2nd while driving at highway speeds. Try to get there by flooring the go-pedal and you'll just bounce off the rev limiter.

    The engine speed is a function of the tire's rolling circumference, final drive ratio, and road speed, as long as you're willing to omit converter slippage. With a locked converter, and assuming no other slippage between flex plate and road surface, you can calculate road speed versus engine speed in each of the available forward gears.

    For a 2007 Dodge Ram 1500 2wd regular cab, Tire Rack lists the OEM tire as the Michelin ATX A/S 245/70R17. Revs per mile (which is revs at 60mph) lists as 690. Standard axle ratio lists as 3.73:1


    So: Tire revs/mile x axle ratio = engine speed at 60mph (assuming direct drive ratio engaged in the transmission and no slippage)
    690 x 3.73 = 2574, which is 2145 at 50mph = about what you observed.

    To find the engine speed at any other road speed when in direct drive, you multiply the engine speed at 60mph by the proposed road speed divided by 60.
    Engine speed at 60mph - 2100rpm
    Engine speed at 50mph - 2100 x (50/60) = 1750
    Engine speed at 40mph - 2100 x (40/60) = 1400
    ...and so on.

    You said rpm is around 1500rpm at 57mph in 5th gear. Since 1500 is about 3/4 of the 2000, it's safe to say 5th gear is roughly 0.75:1. With 1700rpm at 55mph in 4th, the math shows a gear ratio around 0.93:1.

    One strategy available, depending on traffic conditions, is to glide down to 40-45mph before returning from N to D, so the engine speed is a bit lower when 3rd gear engages. Then accelerate gently to coax the transmission to lock up and upshift as soon as possible.
     
  5. Taliesin

    Taliesin Well-Known Member

    Another thing I accidently found out that may or may not make sense:

    If I tap the accelerator pedal shortly before shifting from N to D (pretty much rev matching for 3rd) it actually shifts to 4th sooner. Getting it into 5th pretty much requires 57 mph no matter what I do (if I remember right, it's a .67:1 gear ratio which is pretty close to the 3/4 you mentioned, with 4th being .75:1, and 3rd being 1:1. Any discrepancies can be explained with uncalibrated tach and speedo).

    I really like the truck, but will mainly reserve it's use for why I bought it (towing the boat). I just thought someone might make good use of the information I gleaned during the long weekend.
     
  6. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    Here's a trick I use on my Odyssey. It shifts into 5th at 45 mph. There's no variation to that. However, once it's locked in, it'll hold 5th down to about 41 mph.

    When I hit 42 mph or so, I quickly bump the shifter to N and then back to D. Quickly enough that the rpm doesn't really have time to drop. It'll think for a moment, then drop into 5th gear.
     

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