08 convertible S. My question is regarding the rpm that the car is supposed to upshift, and why that rpm would suddenly go higher? I've driven the car many times, and I don't drive hard, just barely push on the accelerator. People say I drive like an old person, haha! The car generally will upshift around 2,700 rpm. But occasionally it won't upshift until nearly 4,000 rpm. Seems to happen a lot when going up a hill, which I assumed there was some kind of level sensor that when the car knows it's accelerating up a hill will keep it in a lower gear longer. But it also does it on flat roads. Tonight I was coming home and it shifted normal, but then almost immediately down shifted and didn't upshift back into the higher gear until 4k rpm. Keep in mind that I'm not punching the accelerator! Is this just a Mini thing? It's never happened with any other vehicle so I really am curious if its normal. I'm thinking it's not because the previous owner mentioned that he noticed it happening recently before I bought it.

 

Perhaps someone with an auto can chime in here.

 

How many miles on the car and has the trans fluid and filter been serviced.

 

Yep I was going ask the last time the transmission fluid was changed.

 

your trans learns how you drive and adjusts it's self. I can play with accelerator and make it hold in one gear longer and then shift. Like getting on a freeway on ramp. When I track my car I make it shift at a higher point than on the street.

 

I think autos shift when the ratio of throttle pressure:engine load falls below a certain threshold (I assume it has something to do with vacuum, but i'm not sure).

Once you've accelerated up to the maximum speed you can go in a particular gear given the throttle pressure that is being applied, the engine will not be under much load. It will sort of comfortably be "idling" at whatever RPM that is, and the car will not be accelerating or decelerating. At that "equilibrium" point, the ECU will sense that there is not much load, and upshift.

For this reason, the car will hold gear longer on incline, as the engine is under the added load of gravity, and is unable to reach that "equilibrium torque" until it's at higher RPM.
If the car was to upshift like it does on a flat road, you'd likely find that you'd be unable to climb the hill.

As far as random downshifts on a flat road, I have no idea. Maybe the fluid could use a flush, but at the same time, it might not be a good idea if the car has 150k+ mi. Auto trans fluid at that age usually has a considerable amount of metal shavings in it, and flushing it out can reduce the transmission's slippage-preventing abilities. At least, that's what my lifelong family mechanic said one time, and I trust his experience.

Sorry I couldn't be of more help with your particular issue. I wish I knew exactly how shift points are calculated with the auto gearboxes, that would probably be an indicator of the next troubleshooting tips to take. Good luck and let us know how things work out!