Edmunds Answers

Voted Best Answer

  • avatar karjunkie 10/19/08 8:44 am PST

    Had you not said you checked the solenoid pack, that would have been my first guess. Your symptoms are classic bad solenoid pack. However, there is one other potential offender. The transmission control unit (TCU) will often go bad and start the "shift dance" as I like to call it. The main reason for my diagnosis on the TCU is that a bad TCU will correct itself momentarily and then go back to the shifting problem just llike you describe. Usually there are 8-9 electrolytic and tantalum capacitors inside the TCU and you will have to open the TCU and check for some of these being burnt out. To check, remove the TCU and pull
    the cover off, near the connectors there will be one or more burnt electrolytic capacitors.

Answers

  • karjunkie 10/19/08 8:44 am PST

    Had you not said you checked the solenoid pack, that would have been my first guess. Your symptoms are classic bad solenoid pack. However, there is one other potential offender. The transmission control unit (TCU) will often go bad and start the "shift dance" as I like to call it. The main reason for my diagnosis on the TCU is that a bad TCU will correct itself momentarily and then go back to the shifting problem just llike you describe. Usually there are 8-9 electrolytic and tantalum capacitors inside the TCU and you will have to open the TCU and check for some of these being burnt out. To check, remove the TCU and pull
    the cover off, near the connectors there will be one or more burnt electrolytic capacitors.

  • ibeenprobed 10/19/08 2:35 pm PST

    Thanks Karjunkie

    This goes along with my thinking that something is telling the tranny to get stupid. It just works so well when its working. Shifts out perfectly and converter locks up right on que.

    Then has a major brain flatulance. The two gears simaltanouesly really freaked me out.

    Thank goodness is was not going down the expressway or at a high speed and that neutral free wheels everything instantly to prevent internal damage.

    Is the TCU integrated into the ECM module or as a seperate unit? Location?

    I really appreciate the fresh input and I am going to check it ASAP. I will report back my findings.

  • karjunkie 10/19/08 3:42 pm PST

    I'm not much of an expert on Ford automatic transaxles, but I believe it is located towards the top of the transaxle facing the front of the car. Its called the transmission control solenoid and has a black connector into the wiring harness. It is opposite side of the speed sensor connection. Hope that helps!

  • ibeenprobed 10/19/08 5:53 pm PST

    In looking at this diagram;

    http://www.chiltonlibrary.com/content/i
    mages/WD/Ford/194/WD_Ford_194972.pdf


    (let me know if you cannot get to it)

    There is the transmission range sensor which is described as having resistors to vary the voltage to determine shift lever position and pressure. This is located on the forward top of trans and is directly connected to the shaft operating a plunger on the valve body within.

    All other processes are done within the PCM/ECM unit. I will open the TRS and inspect for anything that looks amis.

    After that I will probably drop in a new solenoid pack just to eliminate the possibilty. I did find some information that states the temperature sensor is also integrated into this unit. It cannot be changed seperately and the solenoid unit is about $150 - $200 but as opposed to abandoning the project now it will hopefully work out OK.

  • ibeenprobed 11/03/08 9:00 am PST

    Well Karjunkie my hat is off to you.

    Though the particulars were not exact the concept was spot on. In the Ford realm the sensors are called "Manual lever position sensor" or MLPS (sometimes just MLP).

    In digging around and improving the searches with your ideas I came up with this.

    http://www.transonline.com/transDigest/
    magazines/1998-10/Shift%20Pointers/inde
    x.html


    which is essentially what you were refering to.

    In short, I ordered one, installed it and the car is doing great. This was likely the original problem of the car but with the continued driving it in this condition destroyed the trasmission.

    Make me wonder how many have suffered large transmission repair bills that could have been avoided.

    Thanks again for the help

  • karjunkie 11/03/08 9:48 am PST

    Congratulations! I love to hear it when someone gets it fixed!!! I have had the same problem on BMWs too. They have an electronic shift plate under the shifter mechanism that frequently burns out the contacts and makes the tranny go all wonky! Thanks for letting me know how you tracked down the problem!

  • Art52 01/23/09 12:19 pm PST

    I have a 1995 Ford Probe SE and I have had problems that were like the one that you have mentioned. I found that if the battery terminal is lose or the battery is weak the car shifts

    erratically. I have another problem with this transmission as well, it keeps losing fluid through the high-pressure release valve. This also causes shifting problems over a period of time due to low fluid in the transmission. I have yet to figure out why this does this. I have even changed out the valve, which seemed to help for a short time and then started all over again, maybe you can help with this problem. I wish you the best of luck and hope that I have been of some help to you.

  • manphil 06/13/12 6:55 am PST

    Im late but to all of you with transmission issues, CHANGE YOUR NUETRAL SAFETY switch FIRST, which is located over the top front of your transmission. It may be how your transmissions were damaged in the first place and after you spend $1,500 to rebuild your transmission and it still acts up. This fixed the my Free Spinning problem and the flashing blue dash light. Next,

    Good luck with it, dont give it up and keep sharing any updates so we all can keep ours running smoothly.

  • zigziggo 07/16/12 3:29 am PST

    @ Manphil...


    Do you mean that MLPS? I have had my '97 probe since 2002. I had the transmission rebuilt in '06 with about 120k miles on it (stopped engaging and locked up in reverse). All was fine until just a week ago, after which, out of no where the car will free spin when trying to engage from 2nd to 3rd. If I put it into drive and start off, 1st engages fine, then shifts for 2nd and when it trys to shift to the next gear, the engine just revs up and any acceleration is lost. Of course, the blue O/D light starts blinking. Was this similar to what you were experiencing?

    Thanks in advance,
    Ziggy...

ADVERTISEMENT

Top Transmission Automatic Experts View More

Rank Leader Points
1. karjunkie 5315
2. MrShift@Edmunds 3825
3. zaken1 1235
4. fordfan_17 830
5. snowball2 670
6. tony78 520
7. texases 500
ADVERTISEMENT