Ok I will apologize if this is in the wrong section. And this is a question about a car that is not a Cobalt too. My girlfriend has a 05 Pontiac Sunfire with an automatic transmission. Here lately her car has been acting up. First off, when you take off the car shoots up into high rpms without accelerating that well. Also, sometimes the speedometer will not even work. It will say your going 20 mph when your sitting still or a 110 mph when your driving about 65 mph. I know there has to be something wrong with the tranny..but does anyone have any ideas what could be causing these few issues? I appreciate any help or ideas.

 

bad sensors. sounds like both sensors are dying. Are te RPMs really going up? or is that just what the tachometer is saying? You should be able to hear/feel the difference between the two

 

sounds like youre cluster is taking a dive

 

actually both..you can hear and see them go up

 

well, if you're [ositive the RPMs are actually rising, and its not just the gauge cluster freaking out on you, then it would be a much more serious issue. I really dont know a whole lot about the workings of an auto tranny....but if I HAD to guess, i would say that means your clutch packs are dying, and it isnt engaging the next gear, so its just revving up, trying to clamp down. This is similar to a manual's clutch having no clamping force, but the ECM doesnt know that, so its still trying to shift even without any clutch left