2005 BMW X5 3.0 transmission issues... Please help!!

[Jakesontap]

Thanks!
The tires I have on the X5 now are actually the same diameter, since the rims are wider in the rear it pulls the sidewall down on the rears. I actually took and measured them out and the circumference of the tires were within 1/2" of each other, so on each rotation the bigger tires rotate a 1/2" more which my understanding was well within the 3% you can have. But just to rule that out I am going to install the stock tires back on today. And start from there.
I also have a used trans harness that I will try switching out to see if any of the corrosion got to it or a broken wire.

JCL, the point about the clutch handling the shift is why I am so confused about this issue and wondering what all in involved in the shifting when you use manual verses the programmed shift. If I can rule out the components that are using manual shift versus the components used in automatic shift it will be a start. Wouldn't the vavle/solenoid's be used for both so when I manually tell it to shift the solenoid's do there job correctly?

[JCL]

Originally Posted by Jakesontap

JCL, the point about the clutch handling the shift is why I am so confused about this issue and wondering what all in involved in the shifting when you use manual verses the programmed shift. If I can rule out the components that are using manual shift versus the components used in automatic shift it will be a start. Wouldn't the valve/solenoid's be used for both so when I manually tell it to shift the solenoid's do there job correctly?

When you select a gear you tell it to run in that gear. Not quite the end of the story, because it will override and not let you destroy the engine with over revs, etc, but it starts off knowing it should be in, for example, 2nd.

When it is managing the shifting, it is monitoring things like engine speed, transmission output shaft speed, fluid temperature, pressures in various circuits in the valve body, and so on. Based on all of those, it decides when to shift. It may not be shifting because one or more of those sensors isn't working, or because the signal the sensor is sending is factually correct, but outside the range it should be considering all the other sensors. That is why codes don't tell you what is broken. They tell you what isn't where it is supposed to be, but not why.

Any part of the control and monitoring system could be at fault. I included the actuators because they may still function, but because of a problem not have the correct pressure.

Speaking generally, a test plan is used to narrow down potential causes based on codes and other diagnostic tests. It is cheaper than randomly replacing things (which is often the most expensive way of fixing something). A test plan would include things like checking actuators, pressures at various points, the speed sensor, etc.

Hope that helps. It may be that an expert who overhauls that specific transmission will recognize the combination of codes and suggest a next step. If not, you can use a transmission shop experienced in that transmission (not your dealer) or look for a used transmission or rebuild.