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81 TH350 Lockup or not?

Discussion in 'The Garage' started by MTBLAZER89, Oct 1, 2003.

  1. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    In the process of buying a TH350/208 from an '81. Lockup Yes-No? If it is not can I change the converter or something to make it a lockup? What are the pros/cons of lockup and non-lockup? Is it just an economy thing? Thanks
     
  2. JK5

    JK5 1/2 ton status GMOTM Winner

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    It could be a lock-up style...does it have a plug in the side??? Also a standard converter won't slide on because the input stafts are longer on the lockout style...

    The th350 lock-up style...won't hold-up for wheeling..
    They're a problem trans from day 1!!!
    I've thrown-out a couple. /forums/images/graemlins/tongue.gif

    GM made the lock-out trans to make better gas mileage...

    If you have one...I'd suggest getting a non-lock-out style..
    You'll have much better luck!!! /forums/images/graemlins/deal.gif
     
  3. 77Jimmy

    77Jimmy 1/2 ton status

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    Can you please elaborate on how to tell if a th-350 has a lockup or not? I'd like to know if mine (1977) does or not. Thanks! /forums/images/graemlins/thumb.gif
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    As the other post said,look for a plug and wire coming out of the drivers side of the tranny case behind the gear shift shaft.My 81 G-10 van has a lockup TH350 in it,it drives me nuts always locking and unlocking,it seems the person in front of you knows exactly the right speed to make it do that--very annoying /forums/images/graemlins/angryfire.gif.I have heard they are weak trannys,mines got 187,000 miles on it,but its only had a 250 six and a 307 coupled to it--not enough tourque to pull the foreskin off a misquitoe,so thats not an accurate test of durability /forums/images/graemlins/rotfl.gif.Look for the letters MV4 and the passenger side of the bellhousing,thats a TH350 lockup if it has that code and the wire coming out of the other side.I'm not exactly sure what years used them,but 78-82 sounds about right. /forums/images/graemlins/crazy.gif
     
  5. JK5

    JK5 1/2 ton status GMOTM Winner

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    Your 77' th350 should be a non-lock-out..
    81-82' is the lock-out trans years... /forums/images/graemlins/thumb.gif

    diesel4me is correct...just look for a plug.. /forums/images/graemlins/wink.gif
     
  6. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    So if it's a lockup can I run it without the plug or change something to make it non lockup? Is this bad for the tranny?
     
  7. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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  8. JK5

    JK5 1/2 ton status GMOTM Winner

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    They are different internally... /forums/images/graemlins/frown.gif

    If you don't plug it in...it shouldn't lock-out..

    I had a 78' k-10 someone though a lock-out trans in...it it wasn't plugged-in...it didn't shift that bad....
    I didn't know it was a lock-out until I pulled it...

    Good Luck if you buy-it...hopefully for a good price... /forums/images/graemlins/smile.gif
     
  9. MTBLAZER89

    MTBLAZER89 3/4 ton status Premium Member GMOTM Winner

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    Just lookin for some more opinions anybody else have prob's with these particular trannies? Is it stronger than a 700??? If I just unplug it I know it will run warmer, but won't a Th350 that was non-lockup run warmer too?? I am also gonna run a big stacked plate cooler. /forums/images/graemlins/thumb.gif
     
  10. doctor4x4

    doctor4x4 1/2 ton status

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    totally off subject but
    A big WELCOME to Dieselforme
    and a great introduction with a line like
    "not enough tourque to pull the foreskin off a misquitoe"
    /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif /forums/images/graemlins/rotfl.gif
    now back to reguler secduled program
    iv pullled a lot of tranys and only last mounth did i pull a 350 with a lock up i honestly didnt know what is was
    i sold it cheep 150.00 with my usual guarantee was a good tranny but now after reading this post im glad i sold it
     
  11. dyeager535

    dyeager535 1 ton status Premium Member

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    I don't know as they changed anything that would make the tranny weaker, except maybe the input shaft, as I think they are usually hollow with TCC. The TCC 350 was basically the first of its kind for GM, so as such, it was just an "add on" to the existing design. The 700, 200, and 2004R were as best I can tell, designed with TCC in mind from the get-go.

    It will run hotter running unlocked only, but unless the converter stall speed is higher than a non-lockup tranny, the temperature won't be different. The lockup converter is a great way to run a high stall converter while not developing a lot of heat all the time and still getting good cruise mileage.

    If I were to ever consider going back to an automatic (I won't) I'd figure out how to make it work, and run a decent converter.
     

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