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Thread: 90 Grand Marquis Trans problem

  1. #1

    Question 90 Grand Marquis Trans problem

    My '90 Mercury Grand Marquis, 5.0L (not the police version) is having some transmission problems that started the other day. With 110,000+ miles on it, it will not shift to 3rd or 4th gears. Yesterday, I changed the fluid and filter and gaskets but it did not solve the problem.
    I bought it 2 years ago with 81k miles on it and never had a tranmission problem until now and am hoping there is a simple, inexpensive way to fix it myself. If the pan bolts are too tight, would it cause this problem?

    Thanks!

  2. #2
    Join Date
    Jan 2007
    Posts
    4,850

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    Hi Patriots_fan,

    Sorry you're having this problem. I always have to say this, but you do have a Haynes manual, right? That's always the starting point. As far as the specifics of your problem, diagnosing modern overdrive automatic transmissions can get pretty tricky. The shifting into overdrive is controlled by the computer and its network. Frequently, a problem where it's not shifting into overdrive (4th gear) is caused by a malfunction in the computer and its network of sensors. Is your Check Engine light on? If so, you'll want to check for computer trouble codes - the full procedure is in the Haynes manual.

    You've already done one of the things I would recommend. Changing the fluid and filter can sometimes "fix" automatic transmission problems, particularly those related to the (hydraulic) overdrive function. Another thing is to make sure your fluid level is correct. Sometimes used vehicles have the incorrect dipstick - just a thought.

    Beyond these thoughts, it is probably best to get a professional diagnosis. The transmission in your car has a pretty good reputation for reliability. You can hope it turns out to be something simple.

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