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TH350 - no 2 & 3rd gear?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by hungryjpr, Mar 5, 2002.

  1. hungryjpr

    hungryjpr Registered Member

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    I recently swapped in a TH350/np203. I can feel the tranny shift into gear when I put it in "D", but it doesn't go. 2nd is pretty much the same (almost goes), but in 1st it works fine (so does reverse). I can shift into 2nd, then 3rd once I'm up to speed, & they drive fine. Any ideas on why this is?
    Additional related info:
    All testing done in 2wlo.
    I have the vacuum line hooked up, but not the kickdown due to it being a conversion. I'd like to have the kickdown run for as a manual line if it will work that way.
    Running 42" TSL's. Too much for the TH350?
    Please help - I need to get this thing on the trail!!!
    Matt B
     
  2. muddin4fun

    muddin4fun 3/4 ton status

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    Is the motor reving when you say it won't go? Have you checked the fluid level?
     
  3. hungryjpr

    hungryjpr Registered Member

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    Yes, motor revs up. Basically slips in gear, except 1st. !st is very responsive.
    Matt B
     
  4. Zepplin

    Zepplin 1/2 ton status

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    Mine tranny does the same thing. All the vacuum lines hooked up and I can only get lo gear in 2wd. From what I read on here, its time for a rebuild or a TH400.

    I'm swapping in a TH400 NP205 as we speak.
     
  5. Ryan B.

    Ryan B. 3/4 ton status GMOTM Winner

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    Check fluid level!

    I'll find out what else it could be by looking through a manual later on for ya.

    If it is slipping it sounds like its burning up the tranny clutches dude.
     
  6. hungryjpr

    hungryjpr Registered Member

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    I'm running 2 auxiliary coolers (1 quarts each) plus using 5/8" ID lines to/from each. It took at least 2 gallons to fill the system (can't remember how much though). I checked fluid level, it was fine.
    AFA the clutches, that's what I was afraid of. This was not a brand new tranny - I had it laying around from an old 'burb that got rolled. Hopefully I can get at least a shakedown run outta this one before it's gone.
     
  7. Silver84k5

    Silver84k5 1/2 ton status

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    One time i accidently knocked my tranny into Neutral, then just put it back in gear without letting the motor rev back down, i heard a Big ass BANG, then my tranny started doing the same thing you described, put it in 1st to get going then have to manually go to Drive, when i had it rebuilt, The "Lower Reverse sprag" was cracked all the way through...... just my expierience
     

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