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Thread: P0740 / P0750 Codes With Limp Mode

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    Ramkins2012's Avatar

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    P0740 / P0750 Codes With Limp Mode

    So on my way to work this morning, the converter felt like it either didn’t lock or unlocked and immediately threw a check engine light and went into limp mode.

    I pulled the codes and found.

    P0740: Torque Converter Clutch, No RPM drop at lockup
    P0750: Low Reverse Solenoid Circuit

    The truck has 152,000mi, has been well cared for, and has never given me any transmission problems.

    It has a clean fluid, no burnt smell, etc.

    My research points me to try and replace the Solenoid Pack before I get crazy with a 6-week wait and an entire transmission.

    Does anyone have any experience with these codes or recommendations for me?


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    Outdoornut's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    Solenoid pack would be my first attempt.

    The converter code, I'm not sure.

    My former 2012 started throwing a pressure code on one of the Solenoids.

    I don't remember the code, though.

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  5. Top Of Page | #3
    Ramkins2012's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    I have heard that some of the 68RFEs use the Low Reverse circuit to lock the converter, but I haven’t been able to find much information on it.

    The solenoid pack delivered set me back about $350, so it seems like a good shot before going all out.


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    Permanent Vacation Chrisn162001's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    Yes TCC control uses lR solenoid.

    Start by replacing solenoid pack.


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  9. Top Of Page | #5
    Ramkins2012's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    That is good to hear, and I will be able to tackle the job this Friday as long as everything shows up when it’s supposed to.

    If this works out, I will let everybody know!


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  11. Top Of Page | #6
    Ramkins2012's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    So I said I would update this thread, I’m here to do that, but I’m also here for more help.

    So I used Alpha OBD to clear the codes that I was experiencing, which 100% solved my problem, so I assumed that this also pointed to a solenoid pack that was on its way out.

    I ordered a performance valve body and a new Mopar Solenoid pack.

    The CVI values all looked good, so these items would help prolong the life left in my transmission.

    I finally got everything and installed it all tonight, and I performed a Quicklearn using Alpha OBD and started to go around the block.

    It shifted from 1st to 4th and threw a check engine light. I tried clearing the code P0871, another quick learn, etc., etc., still broke, so tomorrow, I will swap in the old part or parts, I guess, and see what I can figure out.

    Does anyone have any opinions?

    Bad solenoid pack out of the box? Faulty Valve Body?

    Anyone want to buy a truck, LOL.


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  13. Top Of Page | #7
    Ramkins2012's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    Hopefully someone can learn from my pain here.

    This morning I swapped the new solenoid pack back over to the old Valve Body, reinstalled everything, did another quick learn and went for a drive.

    The transmission felt clunky but I attributed that to the learning process and I was very gentle on it. It no longer threw a P0750 code for the solenoid pack and it also wasn’t throwing the P0871 code anymore. This gave me hope that it might live. I worked my way up through 6th and back down several times.

    Eventually, the thing started acting up going into overdrive gears then threw a code for 5th gear ratio (P0735 I think). So I believe that when it was throwing the P0871 code last night it was slipping badly or trying to apply the incorrect clutches some how.

    She’s done!

    This is beyond frustrating but also just how it goes sometimes. I don’t know what happened, my guess is either a faulty Valve Body or the Valve body wasn’t sealing properly against the transmission case. The solenoid pack seems to be okay but it could also be the culprit. I have heard many times that the overdrives can be smoked almost instantly, turns out that is accurate.

    New Transmission time, hopefully I can hear the builders opinions on what could have occurred once he is inside of it.


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    Permanent Vacation Chrisn162001's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    P0871 is for a worn solenoid switch valve bore in the valve body.

    If you don’t replace or rebuild the valve body almost immediately after that code sets, it leads to 5th and 6th failure.


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  16. Top Of Page | #9
    Ramkins2012's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    My whole experience with this has been unique, LOL.

    I never had a P0871 until after putting in the new Valve Body.

    I talked to the builder, and we will see what they find with the valve body.

    The total miles are driven once that code popped up, maybe three, and I was incredibly easy on it.

    Regardless, it’s done for now.


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  18. Top Of Page | #10
    Permanent Vacation Chrisn162001's Avatar

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    Re: P0740 / P0750 Codes With Limp Mode

    Quote Originally Posted by Ramkins2012 View Post
    My whole experience with this has been unique, LOL.

    I never had a P0871 until after putting in the new Valve Body.

    I talked to the builder, and we will see what they find with the valve body.

    The total miles are driven once that code popped up, maybe three, and I was incredibly easy on it.

    Regardless, it’s done for now.


    Sent from my iPhone using Tapatalk
    Yeah, unfortunately, “new” and “built” are very loosely used by a lot of “builders” these days.

    I can’t count how many “new” “built” valve bodies I’ve pulled out of transmissions that were early style non anodized and failed vacuum tests on the SSV.

    Ask your builder if they ream the SSV for the updated Sonnax valve.

    If they don’t, I will find another builder.


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