Mysterious air temp sensitive tranny problem. [Archive] - GrandAmGT.com Forum

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bigtard
09-05-2006, 06:56 PM
I have a 1999 Pontiac Grand Am GT sedan that has a problem that I'm having trouble getting diagnosed.

Sometimes when I shift from Park, Reverse, or Neutral into Drive, the transmission will slip for what is usually 5 to 10 seconds before it is fully engaged. During that time the car moves, albeit slowly.

Here are the unusual things that no one has been able to fully account for yet...

(1) The transmission has *never* slipped in the year and 10,000 miles I've owned it when the outside air temperature has been below about 80 degrees. It *only* acts up when it's warm outside.

(2) The transmission has *never* slipped at any air temperature after the car has sat at rest for 4 or 5 hours. That means in the morning it always shifts into Drive just fine regardless of temperature, and after work it shifts into Drive just fine regardless of temperature.

(3) The transmission only slips after I have been driving the car for a little while (usually at least 10 or 15 minutes, often a bit longer) and shift out of drive into Reverse, Neutal, or Park and then back into Drive.

(4) Once the transmission is done slipping, it shifts perfectly normal regardless of speed, stopping, starting, temperature, etc. until I take it out of Drive again.

(5) Even when it's hot outside, I've driven the car for a while, and I've taken it out of Drive and put it back into Drive, it doesn't always slip. Sometimes it does; sometimes it doesn't. Sometimes it slips after I drive a mile or two to the store, park the car, and later leave; sometimes it doesn't. Sometimes it slips after I drive in stop-and-go traffic and later take it out of Drive; sometimes it doesn't. Sometimes it slips after I have driven hundreds of miles on the highway and later take it out of Drive; sometimes it doesn't.

Most of the mechanics I've talked to completely ignore its *air* temperature sensitivity and just say it needs to be rebuilt. However, one transmission specialist I spoke with today said that he thinks there's a good chance that there's some sort of position sensor or cable linkage going bad, and that's a more likely explanation.

Anyone have any good guesses as to what's going on?

Thanks.

Sprucegagt
09-05-2006, 09:22 PM
It's a guess but this sounds like a pressure control solenoid is going bad. When solenoids start to go bad, they get sensitive to warm/hot temperatures. That's why when the car is cold it works just fine but after you drive for awhile and get heat in the transmission it acts up.

andrewe77
09-05-2006, 09:27 PM
Get the fluid level checked.

bigtard
09-06-2006, 05:42 PM
I have had the fluid level checked when I took the car in to get the transmission flushed. Everything looked fine then, but the problem still happened immediately after that.

As for the solenoid, is there any way to check that or isolate it as a problem without tearing down the transmission?

bigtard
09-19-2006, 02:58 AM
Last week I took it into the transmission shop. They couldn't find the problem. They ended up rebuilding it for more money than I want to think about right now.

The problem is fixed, but I'll never know what exactly the problem was.