diagnosing auto no 4th gear problem

Discussion in 'General Motoring' started by Raymond Cruz, Oct 17, 2004.

  1. Raymond Cruz

    Raymond Cruz Guest

    I bought an 88 240 auto wagon a few months ago with 234K. The transmission
    is quite smooth and fluid is clean and full. However last week I began to
    experience times when the tranny would not shift into 4th gear when the 4th
    gear inhibitor is off, i.e. no illuminated arrow on dash. Note the dash
    light toggles as expected with switch presses. Another way of describing
    this is that cruising at 50MPH and pressing the switch has no effect on
    upshift/downshift and the engine sounds like it is working harder than it
    would in 4th gear (no tach on this car). It may be a little early to
    describe a pattern but it seems as if 4th gear is available when the car is
    cold and then becomes unavailable.

    I found lot of discussion of this problem in old NG posts but I am looking
    for one diagnostic tip. Can I remove the relay and jump contacts in a way
    that would disable inhibiting 4th gear? If I still can't get 4th gear that
    would seem to isolate the problem to wiring from the relay to the solenoid,
    the solenoid, or the tranny itself. If I can get 4th gear that would seem
    to isolate the problem to the relay or perhaps even as some have suggested a
    fuse. One NG article claimed the relay consists of a single switch that
    sends voltage to both the dashboard light and solenoid when 4th is
    inhibited. If true that suggests that simply removing the relay should give
    me what I want.

    RC
     
    Raymond Cruz, Oct 17, 2004
    #1
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  2. Raymond Cruz

    James Sweet Guest


    Removing the relay will not restore 4th gear. Check the wiring under the car
    to the solenoid, also it's possible for the solenoid itself to fail and
    stick closed.
     
    James Sweet, Oct 18, 2004
    #2
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