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Bad vacuum module?

Discussion in 'Automatic Transmission' started by j_dog00, Aug 12, 2019 at 10:37 PM.

  1. j_dog00

    j_dog00 Member

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    This is an easier and shorter post referring to an earlier one. Would a bad vacuum module cause an auto trans to not shift into any gear period? When I pulled it off the back of the trans a little tranny fluid came out, I've ordered a new module just in case. Everything else is good, fluid levels, Torque Converter, flexplate, shift linkage, it's all been checked or replaced. It's just weird that a faulty one would cause a th350 to not shift at all, maybe poor shifting and reduced engine power but not that. I hope it is the issue though it's a cheap fix. Anyone else experience this??

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  2. j_dog00

    j_dog00 Member

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    Module is replaced and still nothing!!!! Please help

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  3. Matt69olds

    Matt69olds Full Access Member

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    Disconnecting the vacuum line will cause line pressure to go to maximum, that may be enough to compensate for a internal hydraulic leak in the forward clutch. But that’s just covering up the symptom, not fixing the problem. It may go into gear, but won’t seal or hold well enough to allow the truck to move under a load. It’s time to drop the transmission pan for an inspection, if the filter is clogged, or there is lots of debris in the pan, it’s time for a rebuild.
     
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  4. 78C10BigTen

    78C10BigTen Full Access Member

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    Did you pull the torque converter out and check the ears?
     
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  5. 78C10BigTen

    78C10BigTen Full Access Member

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    This also happened to me completely outta the blue. I drove it the day before and parked it, next day i backed up and it wouldnt go into any forward gear. I didnt F**K with it i just replaced it with another used trans
     
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  6. j_dog00

    j_dog00 Member

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    78c10 I haven't checked the TC yet I want to do every thing I can first without pulling the tranny, I have no lift and basic tools I'm trying to save the pain for last. The last thing I will do is drop the filter and change that and put new fluid in, if that doesn't work..then I'm dropping it.

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  7. j_dog00

    j_dog00 Member

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    I havent changed the filter yet..who knows when or if it's ever been changed in 39 years.

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  8. j_dog00

    j_dog00 Member

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    Matt69 thank you for reminding me about the tranny filter, haven't checked it yet.

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  9. Matt69olds

    Matt69olds Full Access Member

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    Before spending another dime on it, drop the pan. If it’s full of crud, then replacing anything else would be like putting a band-aid on a gunshot wound. There is also a slim chance just changing the filter would get you rolling again, assuming the problem is a plugged up filter.
     
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  10. j_dog00

    j_dog00 Member

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    Dropping the pan tomorrow..will post pics

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  11. j_dog00

    j_dog00 Member

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    Update!! Dropped the pan, changed the gasket, filter and brand new fluid. However, it will only let me pour on about 5 qts. Of tranny fluid before it spits out the top of the dipstick and it will not let anymore in! I started the engine.let it warm up tried to cycle through all the gears..nothing..no shifting and it still wont let me add anymore fluid..i know it holds 11 qts..th350

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  12. 78C10BigTen

    78C10BigTen Full Access Member

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    If you find that the converter isnt broken and it still wont go in any gear this will be only the second one ive ever heard of this happening to. Mine being the first. Does it go in reverse?
     
  13. j_dog00

    j_dog00 Member

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    No..no reverse or nothing..pulling the TC off to check it tomorrow..still wont let me add more than 5qts its weirs as crap

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  14. 78C10BigTen

    78C10BigTen Full Access Member

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    I wonder if something hasnt moved outta place (that makes shifting possible) inside, and its in the way of fluid going in. Im not sure as ive never been inside of a trans before. Is it 2wd?
     
  15. j_dog00

    j_dog00 Member

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    Weird

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