Overdrive?

Discussion in 'Tow Vehicles, Hitch & Towing' started by frolin, Aug 26, 2014.

  1. Phranc

    Phranc New Member

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    So, I did a little research on the 4L60-E transmission. Before you holler, got to http://en.wikipedia.org/wiki/GM_4L60-E_transmission and see all the applications.

    At any rate, I found the 4L60 service manual and it confirms my description of it's operation. Yes, in Overdrive Range, TC Lockup is inhibited in gears 2-3 at all times, except for excessive RPMs at high speed, and excessive temps.

    Also, in the example given by fix_it, the torque convert will not lock up in a lower gear unless one of two extreme conditions exist.

    The pertinent statements from the service manual are here:



    http://www.grail-ss.com/GRAIL%20Website%20Files/4L60ETechGuide.pdf

    pg 59

    4 TORQUE CONVERTER CLUTCH RELEASED 4a TCC Solenoid Valve:
    ACCUM VALVE
    3-4 SHIFT VALVE
    Under normal operating conditions, in Overdrive Range – Third Gear, the PCM keeps the normally open TCC solenoid valve de- energized. Converter feed fluid exhausts through the solenoid, and spring force keeps the converter clutch valve in the release position. However, at speeds above approximately 121 km/h (75 mph) the PCM will command TCC apply in third gear. Refer to pages 62–63 for more information on TCC apply.

    pg62a

    Note: Under normal operating conditions the torque converter clutch is in the released position during first, second and third gears. However, when the transmission fluid temperatures exceed approximately 121°C (250°F), the PCM will apply the torque converter clutch in second and third gears to help reduce fluid temperatures.

    pg62b

    The PCM monitors for high TCC slip for most models. Excessive slip is recognized by
    (DTC) P1870. The transmission must be in hot mode or experiencing a wide open throttle maneuver in order for the TCC to be commanded on in second and third gear.

    pg64a
    A forced 4-3 downshift in Overdrive range occurs by increasing the throttle valve angle (percentage of accelerator pedal travel or throttle position) while the vehicle is operating in Fourth gear. A 4-3 downshift can also occur when the vehicle is decelerating during coast conditions or when load on the vehicle is increased. Also, if the TCC is applied in Fourth gear it will release prior to the transmission making a 4-3 downshift. Under normal operat- ing conditions the PCM will keep the converter clutch released in Third gear. The TCC also releases under minimum and heavy throttle conditions.
     
  2. joet

    joet Well-Known Member

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    Phranc, This is correct for the 4L60E, and with a little work this trans can be made even stronger, servos and boost valve along with PCM programing. The only way mine comes out of lockup now is to force it with the go pedal. Make a big differance towing.
     
  3. FarmerDave

    FarmerDave Active Member

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    By the time I can afford to buy one they will be well tested lol.

    The new Ecodiesel 1500 RAM with 8 speed torqueflight would be a good one to test out trailering.
     
  4. skeetercampsintexas

    skeetercampsintexas Active Member

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    I'm pickin up what you're steppin in here dave. I'm a big supporter of diesels (if you guys haven't noticed [LOL]). While I was in europe, big or small they were almost all diesels. In fact just the other day I saw a Volkswagen to ROLLING SOME COAL! At any rate, I think the vehicles are going farther for longer, but I'll stick with my trusty old hunk o' junk. 328k miles and it's still on 7 factory injectors.

    As for the tranny, the best advice I think I could ever give is that if it doesn't feel right then don't do it. If you don't run your vehicles into the ground and maintain them they won't leave you disappointed, or waiting for a wrecker.
     
  5. FarmerDave

    FarmerDave Active Member

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    I have no where near 328k on my 7.3 so I'm good for bit, only have about 1/2 that. Being in the snow/salt North the body/frame will die long before the engine will.
     
  6. 96Rockwood

    96Rockwood Member

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    Phranc,

    Not to knock your info, but look at the publish date on that....2000 so just slightly out of date. You see all the notes about the PCM commanding in there. Trush me as the push for FE got stronger and higher the TC was used alot more. Just for example in when tow haul was off in both our 2003 Astro and our 2005 Tahoe, TC was definately on in in 3rd gear even when the PRNDL was in the D4 position. When in town haul TC was in on gears 2nd, 3rd and 4th in both vehicles. This has been confirmed. So while your info was valid at time of publishing, all I am saying is that is doesn't directly apply to your box.
     
  7. Phranc

    Phranc New Member

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    I deliberately left out mention of Tow/Haul Mode because it's not germain to the discussion. Only pickups and van/suvs have that mode, and for the most part we were discussing non Tow/Haul vehicles.

    My 2008 Canyon operates in exactly the way I described. And every 4L60-E without Tow/Haul operates like that.
     
  8. joet

    joet Well-Known Member

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    Also the 2011-2012's opperate this way, as mine did until modifyed
     
  9. 96Rockwood

    96Rockwood Member

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    Not true, but I am out of this discussion at this point.
     
  10. Phranc

    Phranc New Member

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    If you think this isn't true, then post a service manual or such showing that it's not true.
     

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