'99 Buick Park Avenue question

Did anyone see my question about the hard-shift after very slow driving? No comments yet - but there seem to be several of you out there who might have an idea about this. Subject was Transmission trouble? HELP! See way below for more description.


I think what’s happening is, when you drive under these slow conditions, not enough air is passing through the radiator to remove the heat from both the coolant and the transmission fluid. There’s a transmission fluid cooler inside the radiator. As the transmission fluid gets hotter, the powertrain management system thinks the transmission is running hot because there’s a slipping condition in the transmission. The powertrain management system then commands that line pressures within the transmission be increased to prevent what it thinks is a slipping problem. This then results in the transmission shifting very hard and abrupt. Once the vehicle is moving fast enough to remove the heat from the coolant and the transmission fluid, the drivetrain management system then reduces the line pressure and the transmission shifts normally.


Your original post, “Transmission problem? Help!” can be assessed by clicking on your name: 99BuickAZ. Have you checked the transmission fluid level recently? If there is a problem with engine cooling, there could be a problem with transmission fluid cooling, as well. Check it with a mechanic.