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Thread: Automatic Transmission not Shifting

  1. #1
    Member
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    Location:  Greencastle, PA

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    My VIN:    Jan '82 #11153

    Automatic Transmission not Shifting

    Well the new issue is the automatic transmission. I noticed now for a bit, it takes longer to shift from first to second. Now to the point it barely shifts. No problems from second to third although it does it very quickly. I just changed the filter and new fluid. Yes, the level is good. The old fluid was red and no bad burnt smell.

    My thinking is the computer is going or gone. My questions are: Do you need to drop the pan to replace it? If so should you replace the two solenoids? Who makes the best upgraded computer for the money? Do you need to send the old one in to be rebuild or is it safe to buy a new one and hope it fits properly?

    Ah, the fun never stops!

  2. #2
    Senior Member hmcelraft's Avatar
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    It does sound like the computer is on it's way out. A changing shifting pattern is a frequent and fortunate notice - some failures are rather abrupt and damaging. There is a method to replace the computer without dropping the pan. That is by disconnecting the solenoid wiring coming out of the trans at the diagnostic plug in the engine compartment. The wiring pattern at the diagnostic plug must be followed exactly. Take pictures, note colors of the wires, etc. I don't remember the wiring diagrams being very helpful.

    It would be good to see if the old computer could be tested to see just what is going on the fritz. Some people have put some useful self-made testing processes together. I found some on U-tube. That said, I hear good things about DMCH's new "digital" unit but, folks have had good results with thorough inspections and repairs of the old units too. I have used some NOS computers and the Jeep versions too over the years. They all finally failed just like the OEM computers on the cars. Capacitors failed primarily and then, circuit board connections sometimes failed. The transistors in the computers rarely fail and the solenoids in the trans rarely fail. As all gears are activate your solenoids are probably fine.

  3. #3
    Senior Member hmcelraft's Avatar
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    It just occurred to me that there is one issue where a changing 1-2 shifting pattern could mean a more serious issue. It is more telling at the called-for down shift point. Also, are you sure the transmission is holding in 3rd gear - no slipping? A loss of fluid pressure internally can cause a higher 1-2 shift point and 3-2 or 2-1 downshift point. If you detect slippage in 3rd gear - well, problem is internal. Disconnect the "down-shift" wire coming from the switch at the throttle spool when you test. I would leave it disconnected - that switch usually causes more problems than not. If the computer has any where near 30,000 miles on it - I would definitely go computer first. Seems that NOS OEM computers went 30,000 or sooner.

  4. #4
    Senior Member Jonathan's Avatar
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    Sounds like the shift computer is the problem to me.

    When mine failed, I replaced it with a rebuilt one from DMCMW. It will need to come out completely, and yes that means the pan gets dropped to access all of the connections. You will end up putting in new fluid, but the filter can stay as you mentioned you just replaced it.

    Generally speaking, they rebuild yours with new components/circuitry. It is supposed to be based on your CORE unit being repairable. I do not believe you can just go buy a new one without giving them your old one. They just don't exist off the shelf like that. The expectation is that yours is not too far gone to be repaired. That normally means the wiring isn't melted badly more so than what the condition of the inside of the computer box is.

    You may be permitted to get your new one in advance, after paying the rebuild charge plus the core charge, and then having the new one put in at the same time you take the old one out. This helps a lot if you are getting a mechanic to do the work for you, otherwise your car sits in his shop while you mail off your old one and wait to get your new one back. This will be contingent on how many they might have waiting in inventory (rebuilt ones) and what the condition of the one you send them is believed to be in.

    I would suggest calling your favorite DMC vendor and speaking to them about your options. Keep in mind that you might be getting the last guy's shift computer core and someone else will be getting yours at a later date. Pay it forward, if you will. You can't go back and change the condition of your shift computer wiring now if indeed it already is damaged, of course. Just keep in mind this is how the "exchange" has historically worked.
    One damn minute Admiral...


  5. #5
    Admins Never Retire Ron's Avatar
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    It sounds like the capacitor(s) are finally going out to me too...

    You can check the GC behavior easily using a couple of small light bulbs...see link HERE. As mentioned, you can remove the GC w/o dropping the pan and send it to the vendor for testing/repair/replacement, but they prefer you send the Multifunction Switch so it and its harness can be checked. If you go this route, note that two of the brass fasteners ("A" and "E" in above link) should not be disturbed. They are molded in place I.E They look like hex nuts, but turning them will ruin the unit...
    If you are confortable using a soldering iron on small parts, everything you need to know is in that thread...and then some ;-)

  6. #6
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    Well I don't want to mess with this again so I'll pull everything out and get it updated and replaced.

  7. #7
    Ramblin' Wreck from Georgia Tech RamblinDMC's Avatar
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    I had great success replacing the capacitors and main power transistors in my GC. It only cost me about $10 too.

    Sent from my XT1049 using Tapatalk

  8. #8
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    Ok. I pulled everything out including the solenoids. One problem. I didn't mark them. Does anybody know which solenoid goes on which side. One has a grey cover wires and the other has clear/copper looking wires.

  9. #9
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    I found out from DMC that the solenoid with the clear wire goes on the passenger side. Also, I would like to thank the great guys at the Rocky Mountain DeLorean Club here in Denver for their help in getting my transmission computer replaced and running great - Dan, Matt and Peter. Installed an after market Gullwing Design unit.

  10. #10
    Senior Member
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    why the solenoids ?

    never heard that those in the tranny failed. those in the doors yes, but not in the tranny.

    number one failing problem is the solder joints NOT the capacitors.

    not resoldering or even better - replacing the PCB - will lead to the same problem soon.

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