48RE Question/Issue

Discussion in 'General Discussion' started by Tincup, Aug 11, 2022.

Car Parts
  1. Tincup

    Tincup Full Access Member

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    I've been driving my truck for about a year now, and it has been working great. But I've noticed that when I slow down (10-15Mph) it doesn't downshift properly, It can't seem to find 2nd gear, it slips. It upshifts awesome, very firm and crisp shifts, it only happens when slowing down. The trans only has about 32K on it (2k from me). Before installing, I installed all new electronics ( New Governor Solenoid GM style, pressure sensor, lock up solenoid), Billet accumulator, Trans-Go shift kit, new fluid + Filter (Mopar ATF+4).
    Not sure what else to check, any suggestions would be appreciated. 20210501_181601.jpg
     
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  2. Kiwi SRT10

    Kiwi SRT10 Well-Known Member Supporting Member

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    I love that truck, well done.
    I am no use on auto trannies.
     
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  3. Srt10650

    Srt10650 Full Access Member

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    Maybe the bands need adjustments or maybe the tv cable as well.
     
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  4. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    The 48re doesn't use 2nd gear on deceleration but rather shifts from 3rd to first, by design.

    If it feels odd during deceleration (has changed and IS trying to use 2nd for example), it is typically a pressure sensor/transducer that is acting up.

    The 48RE is also touchy with fluid level. It needs to be full.

    Diagnosing Trans issues via words can be tricky.
     
    Last edited: Aug 12, 2022
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  5. Tincup

    Tincup Full Access Member

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    Thanks as usual Ronnie, It does have a new pressure transducer, I'll double check the fluid level.
     
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  6. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    The GM Solenoids are generally reliable although their shape can prevent a good seal on their base. You can often see marks on the 48RE case where they've been contacting, if you pop one off and have a look. Something to check.

    Transducers have been known to be faulty out of the box and/or fail in a short time.
     
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  7. AMS3

    AMS3 Well-Known Member

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    I used to think the same thing before I had mine rebuilt. Thought it was missing second as well. Once I had the tranny rebuilt, it continued to do it. Kinda odd it's designed that way, but it is. I also have the trans go shift kit. It can bark the tires shifting into second if you get on it. Whole damn truck shakes, LOL.
     
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  8. Tincup

    Tincup Full Access Member

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    Found the problem, turns out the kickdown lever on the trans was loose. I tightened that up and now it shifts like a animal, so now I'm adjusting the TV cable to calm it back down.
     
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  9. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    That's an easy fix but certainly hard to diagnose a loose Kickdown Lever. ;)

    The TV can be a touchy adjustment.
    As you likely know, it has to move as soon as the throttle moves, even the smallest amount.

    Glad you found it!

    Somewhere between shifts that loosen fillings (and hang onto gears before shifting) and sloppy/sliding shifts lives the elusive adjustment sweet spot.
     
    Last edited: Aug 17, 2022
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  10. Tincup

    Tincup Full Access Member

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    Here's one for you Ronnie, I Got it shifting pretty good, but now when I come to a stop it stalls??? any idea why?
     
  11. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    I'd think about what else was changed when you set the TV.
    I mean even if your throttle body was closed, the Idle Air Motor would provide bypass air to keep your engine running as it compensates for engine load.

    Are you saying it won't idle in Drive with your foot on the brake???

    Does it otherwise idle in Park or Nuetral?

    And you do have a spring pulling the kick down lever forward...right??
     
    Last edited: Aug 19, 2022
  12. Tincup

    Tincup Full Access Member

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    That's just it, I can't figure out if the two are related, or just coincidence.
    It idles fine in park or drive with foot on brake. (Haven't checked neutral)
    Yes, I do have the return spring on the kickdown.

    What should the engine idle at? I'm about 800 in park, and maybe 700 in drive.

    The only other thing I touched was I set the second gear band adjustment ( torque to 72In/lbs then back off 1 3/4 Turns) that's when I noticed the loose lever.
     
  13. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    I'd pull your idle air motor out and make sure it's clean.
    My own vehicle maintains the same idle speed whether in park/nuetral or Drive with my foot on the brake. That's the job of the idle air motor.
     
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  14. rottenronnie

    rottenronnie Well-Known Member Supporting Member

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    Mine is cammed but I believe stock idle to be around 8 or 850 rpm, (maybe 900, I forget);
    Regardless, the idle speed is controlled by the ECU.
     
    Last edited: Sep 7, 2022