Z32 Auto transmission issues

Discussion in 'Technical' started by Evets264, Apr 6, 2020.

  1. Evets264

    Evets264 New Member

    Hi, I have a 1991 300zx, non-turbo automatic. When I'm cruising down highway, in either 4th or O/Drive, it'll just drop a gear by itself. Once accelerating a bit and backing off, car will go back into correct gear for speed. Not long after it will drop a gear down again.
    Has anyone experienced anything similar and found what fault it is?
    I will be servicing transmission in the next week or so but thought I'd put feelers out to see if there is anything else I should look at as well.

    ADAMZX 2000spec Conversion

    It could be a faulty auto ecu module. From what i know they go bad after all these years of use, Its evitable unfortunately.

    If you can, check the auto fault codes using conzult and see if anything comes up and if need be service the trans. if all that doesnt solve the problem i would recommend replacing the auto ecu with a used one or have it reburished by injectronics through repco.
  3. Evets264

    Evets264 New Member

    Thanks AdamZX. I take your suggestions on board. Appreciate it.
    ADAMZX likes this.
  4. ivan129

    ivan129 Active Member

    Assuming these are the only symptoms of your problem, then it does sound like a problem to do with electronic control of the transmission. ie. electrical.
  5. brisz

    brisz Well-Known Member

    How old is the TPS and is it adjusted correctly ?
    MickW likes this.
  6. MickW

    MickW Carntry member...

    Mate, how long have you had the car? Had it been OK until recently and then it started to mis-behave?

    What speeds does this occur at? You said "highway" but do you have the problem more on slightly uphill stretches? Maybe the lockup clutch is cutting in and out as designed.

    2nd BrisZ about the TPS. It's crucial. And every TPS develops worn spots at the standard cruising speeds i.e. 60 kph, 80 kph, 100 kph. It's just a potentiometer, with a rotating wiper against a graphite bed, same as a volume control on an old radio.

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