1999 Pontiac Grand Prix Transmission Slipping

1999 Pontiac Grand Prix GTP. I will turn the car on and drive it around for 5 to 10 minutes and it shifts good, no slipping, it goes in reverse and back in drive normal. But after 10 minutes of driving it stops  shifting like if its in neutral. I put it in drive or reverse and nothing happens.

ill turn off the car for 10 minutes  and it starts to work fine for another 10 minutes.the fluid level is fine,check the linkage and it is not loose. Is there a sensor that's can go out that can cause this.

Answer: This sounds like two possible causes.
The fact that you say it is like it went into neutral is the key. This could be a valve body problem.
There are many valves in the valve body that control most shifting functions. If certain one(s) were to stick, that will cause the transmission to go into neutral.


Another possibility is a problem with the pressure control solenoid. This solenoid does what it says- controls pressure. If it was bad, it could cause low transmission line pressure- and thus no shifting and loss of the gear you were in.


I would suggest a trans filter and fluid change, along with complete system flush. A system flush removes ALL fluid from trans., while a filter and fluid change only replaces approx. 5-6 quarts of fluid. This flush will also have a cleaning solvent put in the system, and this may help to free up a sticking valve.


Engine RPM Bounce

2000 Pontiac Grand Prix 3800 v6.
When cruising at steady speed, then lightly accelerate car's rpm bounces back and forth causing car to buck. Also will hard shift but not very often.  wasn't sure if engine or transmission related?

Answer: Could be either an engine misfire, or a transmission problem. When hitting the gas slightly from a steady speed, this put a big electrical load on the ignition system. If a spark plug wire were weak, it would then cause a misfire, and the conditions you have. The rear plug wires are especially common for this. They spark would arc through the metal collar around the plug wire at the spark plug. You can check this by spraying water from a spray bottle on the plug wires when at idle. Many times this will cause a weak wire to arc. Or you can but car in gear, hold brake firmly, and press and hold the gas pedal about 1/4 way down as someone sprays water. This is know as a brake torque. This causes a heavy load on the ignition.

The trans problem would be a Torque Converter Clutch (TCC) problem. When hitting the gas in this manner, the TCC disengages- almost like a small downshift. If it were malfunctioning, it go on and off, and give your condition. Usually will have a code in the computer- may or may not set a check engine light.

But the engine misfire is most common.



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Comments (16)
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  • Guest - Truus

    So, can you help me to take out my key?

  • Guest - Tech

    In reply to: Guest - Truus

    Sounds like a problem in the shifter release solenoid. They stick or get full of poop and then stick. It is located inside the shifter assembly. It would all need to come apart and checked.

  • Guest - john

    1999 Grand Prix supercharged. I can shift transmission manually and works fine,but won't shift on its own. Motor is misfiring all of a sudden also. Could this be because of transmission?

  • Guest - Tom

    If the only way the transmission is shifting is by using manual 1 and 2, then you have an internal engine problem. That would not cause the engine to misfire.

  • Guest - Guest

    I have a 2000 Pontiac grand prix gt, I drove about two hundred miles today. the last ten miles my car bogged down when it shifted into second, I disconnected the battery cables and let sit for ten minutes. after this the car was back to normal. any suggestions on what my problem could be?

  • Guest - Sammy

    In reply to: Guest - Guest

    Possibly a bad shift solenoid.

  • Guest - john

    I have a 1999grand prix gt I was driveing and lost drive so I come home and put it in park no gears after that I shut it off anf waited 5 to 10 min started it back up and had 1 2 overdrive changed fluids and filter

  • Guest - Stan

    In reply to: Guest - john

    I have a 1999grand prix gt I was driveing and lost drive so I come home and put it in park no gears after that I shut it off anf waited 5 to 10 min started it back up and had 1 2 overdrive changed fluids and filter
    <br />Sounds like your transmission has a bad pressure control solenoid.

  • Guest - mike

    I have a 1999 grand prix gt and it acts like it doesnt want to shift from first to second after i accelerate from a complete stop after having been running for a little while iv already changed the fluid and filter in the transmission

  • Guest - paul

    I have a 1999 Pontiac grand prix and the transmission does want to shift out of 3rd into overdrive afther the car gets warmed up and its getting worst what do u think it maybe?

  • Guest - DJ

    I have a 2001 Pontiac grand prix n my car won't go in drive or reverse I put fluid in the trans n it's still not moving

  • Guest - Sammy

    In reply to: Guest - DJ

    Make sure that the shifter is actually moving the lever on the transmission. If it is and it is full, then sounds like the trans is shot and needs to come out and get repaired or replaced.