Drivetrain I Need Aode Help. Shifting All Messed Up.

Discussion in '1994 - 1995 Specific Tech' started by ratio411, Aug 23, 2012.


  1. ratio411

    ratio411 Founding Member

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    94 GT AODE w/4.10 gears.

    New condition.

    My son's car.
    He complained that all the sudden the car is revving really high in 1st before it will shift to 2nd.
    Depending on throttle, he said it wouldn't shift into 2nd gear before 4k rpm. Even later if you were harder on the throttle. It wouldn't shift at it's normal 1-2 point. Then the next shift is too soon.

    So I drive the car. Here is what it is doing, and I am baffled:

    With gear selector in "D", taking off from a stop, easy normal driving.
    It runs up to 4k rpm then shifts from 1st to 3rd.
    Then goes to 4th at a little lower rpm than it used to.

    So I try it again. Taking off from a stop, easy driving, but with gear selector in 1st.
    Then, at about the normal shift point, way before 4k, I manually shift to second, to see if it jumps to third or holds 1st up to the higher rpm. Nope. It instantly, and effortlessly shifts into 2nd!

    So then I continue through 2nd, up to about a 'normal' rpm for a 2-3 shift, then put it in drive.
    The tranny seems to shift instantly and easily, like the previous manual shift, but it is quickly apparent that it shifted out of 2, but either did not go right to 3, OR went into 3 but slipped as though it was in neutral. After about 2-3 seconds of slipping, it kinda started catching 3rd and drove again, without slippage. Then 4th came too soon and it learched into OD.

    So, in automatic mode, it shifts high and hard from 1 to 3, then mushes into OD.
    In manual mode, it shifts perfectly 1 to 2, but 2 to 3 is either super slow or 3 slips at first.
    4th is mushy and too soon again.

    IDEAS?
    #1
  2. ratio411

    ratio411 Founding Member

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    Oh, forgot to mention, no CEL.
    My other son is going to put his code reader on it tomorrow anyway though.
    The electric fan is running ALL the time now. Even if you start the car dead cold.
    I don't recall it doing that before. Could be related????
    #2
  3. toyman

    toyman SN Certified Technician

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    My guess is it will be one of the following:
    Transmission Range (TR) Sensor
    Shift solenoid 3 (SS3)
    Transmission speed sensor (TSS)
    #3
  4. 88LX5.Oh

    88LX5.Oh Advanced Member

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    Also for ****s and giggles, check the TPS voltage. In an electronically controlled transmission, the TPS plays a huge roll in transmission performance. High voltage usually results in very high or delayed shift points (much like your described auto 1-2 shift). Since it's a '94, you can hook it to a GOOD scanner and do a throttle position sweep and see the voltage from the scanner. No messing with wires lol.
    #4
  5. BANGERSTANGER76

    BANGERSTANGER76 Member

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    FIRST MAKE SURE THE FLUID IS GOOD.
    Check the Trans pan and magnet for any metal shavings. If no shavings. I would change the Neutral saftey switch located on the left side of the trans. Solved my problem beautifully. Good luck.
    #5
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  6. ratio411

    ratio411 Founding Member

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    Well, we put a code reader on the car today...
    We got a code for "Coolant temp higher or lower than expected"... This probably explains why his electric fan is running all the time. I assume the ECT is bad, and it is less than a year old. :mad:
    I wonder if the PCM thinks that the engine is overheating, if it tinkers with the transmission functions?

    So, the engine is getting false high readings from the ECT.
    That was the only code.

    When you say "neutral safety switch", do you mean the MLPS?
    That was a suspect in my mind, and probably will be changed.

    Also, the tranny started acting up when the fan started running constantly. Coincidence?

    The fluid was about a half a quart low when hot, idling in "D", on a level road.
    It is dark, but definately not burnt or smelly.
    The fluid was last changed in 2010. Was in great shape then.
    We'll probably change the fluid over to Mercon V as suggested on some forums.

    Forgot to mention, the car has a very large tranny cooler. It never runs any kind of hot. Neither does the engine.

    Any other thoughts?
    Thanks for all those ideas so far!
    #6
  7. ratio411

    ratio411 Founding Member

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    I changed the TPS about a year ago.
    I intend to check the volts, but haven't had a chance yet.

    No codes involving the TPS.
    The TPS is not a Motorcraft, like everyone likes, but it sure was expensive anyway.
    I admit that it is possible the unit is a cheapo and gone bad, I just need a chance to check it before throwing more money at it.
    My son left for work and won't be home until late tonight. I told him to baby the car, he has nothing else to drive.

    What is really bothering me is the difference in outcomes between auto shifting and manual shifting...
    It skips second and shifts into third without issue in auto mode, but when manually shifted it will go right into second, and then neutral out (freewheel, slip, not move under throttle, whatever you want to call it) when it goes into third, then pick up third after a moment, as though nothing happened. Two totally different outcomes. So I know 2nd gear is not out, and I know that even though 2-3 shift is mush, it doesn't slip unless it is manually shifted.

    I think I am boiling it down to MLPS after composing the symtoms again.
    #7
  8. Chythar

    Chythar Well-Known Member

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    I think the troubleshooting tips above are good, but are in the wrong direction. For "Coolant temp higher or lower than expected" codes, you'll get that if the car is not at operating temperature. Clear the codes and check again after coming back from a drive. As to the unusual transmission shifting, the "problem" is caused by the 4.10 gears in the rear end. The computer shifts the tranny mainly based on throttle (how hard you push on the gas). This is timed based on the stock rear gear set. By putting in the 4.10's, you're reaching high rpm's faster then the computer is expecting and it's getting confused. This happens with every Mustang with an automatic when they change the rear gears.

    To fix it, you'll need to get a chip for the computer to change the shift points, so it knows to shift gears sooner than it does now. You can buy a chip and program it yourself, or you can pay someone for it. I'd recommend doing it yourself so you can fine-tune the shift points.
    #8
  9. 68keyblr

    68keyblr Member

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    Check in with Dan Gilsdorf at www.silverfoxtrans.com . Super knowledgeable about AODs and has always helped me with questions.
    #9
  10. ratio411

    ratio411 Founding Member

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    The car is already calibrated for the gears.
    That was done the same time as the gear change.
    This problem is new. The gears have been in the car.

    As for the temp, it didn't matter if the car was hot or cold, and the fan just started running all the time.
    That's how I know it's a false high. If it was a false low reading, the fan wouldn't run at all.
    #10
  11. ratio411

    ratio411 Founding Member

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    The car has a chip, but this problem with the tranny is the same with or without the tune.
    We reset it to stock just to make sure.
    #11
  12. ratio411

    ratio411 Founding Member

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    Thank you for the lead!
    I sent him an email.

    I hope I can repay him with business one day.
    His website parts descriptions and knowledge is impressive.
    #12
  13. 88LX5.Oh

    88LX5.Oh Advanced Member

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    First thing tomorrow morning I'll look in my ATSG manual for EVERY electronic device that has anything to do with the trans. That way it can help you eliminate the electronics portion of it.

    Usually when I scan a vehicle and get no codes, it's a mechanical problem
    #13
  14. ratio411

    ratio411 Founding Member

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    Well, I am hoping that the code on the ECT applies.
    I am hoping that the PCM is screwing up the shifting because it 'thinks' the engine is overheating.
    It's too much for me to believe that the ECT malfunctions at the same time it starts the shifting problem, yet they are unrelated.

    I am going to look hard at the MLPS as well. I have had them malfunction on other vehicles without setting a code.
    #14
  15. Bullitt95

    Bullitt95 Active Member

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    Check that the wiring connector to the ECT sensor hasn't come loose and isn't making proper contact. If it's OK, then check the resistance across the two wires when the engine's cold. Unless it's a blazing hot day it should be at least 20K ohms. If it's much lower than that, the sensor has an internal short and it'll fool the engine computer into thinking that the engine's hot, triggering the electric fan to stay on constantly unless you switch off the ignition.
    As for the tranny shifting issue, first replace the tranny fluid/filter and if that doesn't solve it, replace the MLPS.
    #15
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  16. BANGERSTANGER76

    BANGERSTANGER76 Member

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    Yessszziiiiirrrr.
    #16
  17. 88LX5.Oh

    88LX5.Oh Advanced Member

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    Taken directly from the ATSG AODE Techtran manual

    AOD-E Transmission Electronic Control System
    The following is a list of the actuators and sensors used in controlling the transmission
    - Electronic Control Microprocessor Assembly (ECA)

    INPUTS
    - Engine Coolant Temperature (ECT) Sensor
    - Air Charge Temperature (ACT) Sensor
    - Transmission Operating Temperature (TOT) Sensor
    - Manual Lever Postion Sensor (MLPS)
    - Brake ON/OFF (BOO) Switch
    - Electronic Distributorless Ignition System (This doesn't apply to anyone here so I will omit the trans function and symptoms later in this reply)
    - Air Conditioning Clutch (ACC)
    - Mass Airflow (MAF) Sensor
    - Throttle Position (TP) sensor
    - Output Shaft Speed (OSS) Sensor
    - Vehicle Speed Sensor (VSS)

    OUTPUTS

    - Shift Solenoid Assembly
    -- Shift Solenoid 1 (SS-1)
    -- Shift Solenoid 2 (SS-2)
    - Electronic Pressure Control (EPC) Solenoid
    - Modulated Converter Clutch Control (MCCC)




    ECT Trans Function - ECT is used to control modulated converter clutch operation.
    Symptoms: Modulated converter clutch will always be off, resulting in reduced fuel economy.
    Fault codes 116, 117, and 118
    (This effects lock up only and probably not the root of your issue)

    ACT Trans function - ACT is used to determine EPC pressure.
    Symptoms - Incorrect EPC pressure either high or low will result in either harsh or soft shifts.
    Fault codes 114, 112, and 113

    TOT Sensor Trans fuction - The microprocessor assembly uses this voltage signal to determine whether a cold start shift schedule is necessary. The shift schedule is compensated when the transmission fluid is cold. The microprocessor also inhibits converter clutch operation at low transmission fluid temperatures and corrects EPC pressures for temperatures.
    Symptoms - Converter clutch engagement and stabilized shift schedules happen too soon after a cold start
    Fault Codes - 636, 637, 638

    Manual Lever Position Sensor (MLPS) - The MLPS sends a signal to the microprocessor assembly which indicates of the shift lever (P, R,N, OD, D, 1). The MLPS is located on the outside of the transmission on the manual lever shaft.
    MLPS Trans Function - Determines desired gear and EPC pressure.
    Symptoms - Engagement concers, wrong gear, no shifts.
    Fault codes - 634 and 522
    NOTE: The sensor also contains the neutral/start and back up lamp circuits

    Brake ON/OFF (BOO) Switch
    Trans Function - Disengage converter clutch when brake is applied.
    Symptoms - Failed "ON" - converter clutch will not engage at less than one-third throttle.
    Failed "OFF" or not connected - converter clutch will not disengage when brake is applied.
    Fault Code - 536

    Air Conditioning Clutch (ACC)
    Trans function - Adjust EPC pressure when A/C compressor clutch is engaged to compensate for additional load on the engine.
    Symptoms -
    Failed "ON" - EPC pressure slightly low with A/C OFF
    Failed "ON" - EPC pressure slightly high with A/C ON.
    Fault Code - 539

    MAF Sensor Trans function - EPC pressure control, shift and converter clutch scheduling
    Symptoms - High/low EPC pressure, incorrect shift schedule, incorrect converter engagement scheduling and symptoms similar to TPS malfunction
    Fault Codes - 157, 158, 159, 184, and 185

    TPS Trans function - Shift scheduling, EPC pressure control, converter clutch control.
    Symptoms - harsh engagements, firm shift feel, abnormal shift schedule, converter clutch does no engage, converter clutch cycling (lock up coming in an out)
    Fault codes - 121, 122, 123, 124, 125, and 167

    Output Shaft Speed Sensor Trans function - converter clutch control, shift scheduling, used in determining EPC pressure.
    Symptoms - No converter engagements, harsh shifts, abnormal shift schedules.
    Fault code - 639

    VSS Trans function - modifies upshift schedules
    Symptoms - shift busyiness on grades
    Fault code - 452

    Shift Solenoid Assembly (SS-1 and SS-2)
    Trans function - Solenoids 1 and 2 provide gear selection of first through fourth gears by controlling the pressure to the three shift valves.
    SS-1 Symptoms:
    Failed "ON" - first and fourth gear only
    Failed "OFF" - second and third gear only
    Fault codes - 617**, 618**, 619**, and 621*
    SS-2 Symptoms:
    Failed "ON" - third and fourth gear only
    Failed "OFF" - first and second gear only
    SS-1 AND SS-2 symptoms:
    Both failed "ON" - fourth gear only
    Both failed "OFF - second gear only
    Fault codes - 621* and 622*
    * Output circuit check, generated only by electrical conditions
    ** May also be generated by some non-electrical transmission component condition

    Modulate Converter Clutch Control (MCCC) trans function - Used to engage the converter clutch
    Symptoms:
    Failed "ON" - engine stalls in second gear (OD, D range) at low idle speeds with the brake applied.
    Failed "OFF" - converter never engages
    Fault codes - 628** and 652*
    * Output circuit check, generated only by electrical conditions
    ** May also be generated by some non-electrical transmission component condition

    Electronic Pressure Control (EPC) solenoid trans function - Regulates EPC pressure, 2-3 back out valve control, line pressure.
    Symptoms:
    Failed "ON" - minimum EPC pressure (minimum capacity), limit engine torque (alternate firing).
    Failed "OFF" - maximum EPC pressure, harsh engagements and harsh shifts.
    Fault codes - 624 and 625
    #17
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  18. ratio411

    ratio411 Founding Member

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    Thanks for that.
    It confirms that the ECT does have an affect, even if it isn't the root cause.

    It also makes me focus even more on the MLPS.
    The symptoms listed for the MLPS are a bit vague, but can fit what is going on.

    After the distributor cap adapter screws came loose on this car, it is not a stretch to think the MLPS couldn't get loose and misadjusted too.
    #18

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