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700R4 shifts into OD while in D

Discussion in 'The Garage' started by PhilS10HO, Feb 10, 2007.

  1. PhilS10HO

    PhilS10HO Registered Member

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    Location:
    NH, Carrol County
    1987 1/2 ton GMC 700R4 350 10 B's 35's

    Since I bought the truck I've always driven it in D. Lately it's been shifting inot overdrive anyway. Pretty soon too. Around 35-40mph under normal driving. Give it about 1/3 throttle and it'll drop into 3rd, but doesn't stay there. I know the tranny isn't happy already from the burnt smelling fluid. It was dark until I changed it a few times and cleaned it out. I know driving it in overdrive is just gonna burn it up faster with my 3.42's and 35's. So if anyone can make any suggestions to take care of this it'd be a big help. Maybe sometihng not adjusted right? Don't have it in my budget for a new tranny right now. This is my DD by the way.

    Phil
     
  2. sandawgk5

    sandawgk5 3/4 ton status

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    It is not going into OD it is locking the torque converter which drops RPM ~500. When the selector is in D and not OD it lets the converter lock in 3rd also. The in and out is just a problem with GMs highway geared axles and a heavy rig. I run 4.10s with 37s and it still does it.

    Ira
     
  3. PhilS10HO

    PhilS10HO Registered Member

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    I've been driving it prolly 4 months and it does this on and off once in a while. Lately it's been really bad though. I thought it was shifting in OD because I put it in OD on purpose to make sure that's what it was actually doing, and there was no rpm change. I do have a tach. It was doing this to me around 35mph on the way home in a snow storm a few weeks ago. it would up shift. So it wouldn't quite bog, but not have the power to move the truck at 1000rpm either. So i'd have to give it some gas to downshift then the tires spin from the sudden rpm jump. Fun fun.


    Does anyone run a non lock up converter for this very reason?

    Phil
     
  4. sandawgk5

    sandawgk5 3/4 ton status

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    A non lockup converter will heat the fluid too much unless you have a huge cooler on it and then, 700r4s that are pretty finicky with temp, will burn up. I do not know if anyone makes a non lockup converter for a 700.

    Ira
     

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