2007 BMW X3 AT6 Transmission/trasnfer case

[apfehr]

I've searched high and low for forums that seems similar to the issues I'm experiencing with no avail as the issues I face are weird to say the least. For example, 2 weeks will pass and the car will drive PEREFCT. Then one day I'll wake up and the car bucks, hesitates, slips, I hear grinding up front where it seems the front is attempting to engage AWD.
When its acting up symptoms as follows:
Leaving from a stop the car lacks power but never goes into safe mode. Between gear change 1-2 it completely falls on its face - the only way to get it moving past 10mph is to floor it - which still takes 1-3 seconds for it to react and downshift back to 1st and start moving - almost like the car stalled. From 2-3 it slips between the gear change - Falls on its face and slips/revs up from 2000-4500RPM before engaging 3rd. It does this between every gear change. Once finally reaching 6th gear and cruising on the freeway its TOLERABLE, but will buck and hesitate at random particularly uphill on the freeway. again - the only way to get rid of it is either let off and try again or floor it. Sometimes I'll hear a metallic popping/grinding from the front end at lower speeds. Only fault I have on the dash is a CEL for a lean condition in banks 1 & 2 which ALSO is intermittent. Some days its present, some days it's not. Occasionally I get the yellow 4x4 light in combination with the brake light which I know is the actuator arm for the TC - But that shouldn't be causing this and only is on for 2-3 drive cycles if even that and will disappear. I'm extremely mechanically inclined but I feel like this is out of my hands as I'm driving around a giant computer with wheels. Any ideas?

[91e34M5]

From the symptoms you describe, it almost sounds like you may have two different issues, drive train and engine....or it may just be and engine issue that carries over to the AWD system. What kind of code reader are you using? Is your code reader capable of reading transmission module codes? My X3 has a different engine than yours, but my daughters e90 has basically the same engine. About a year ago, my daughter's e90 started having very unusual symptoms, the trans would go into safe mode, engine misfired, lack of power, etc. If she stopped and restarted the engine, the symptoms would go away for a day or so, but they always came back. My code reader registered lean codes, but nothing else. I took the car to my trusted indy shop for a full diagnostic to find that the crankshaft position sensor was sending faulty signals. He advised that faulty signals from the Crank Sensor can affect most every computer module in the car, including transmission, ignition, engine management and cause all sorts of odd symptoms. I changed the sensor out myself and the problems went away. It's possible that there was a poor connection at the sensor that was causing the problem because the connector was oil soaked. I cleaned the connector plug before I reconnected the new sensor.
All told...you might want to consider getting a full diagnostic from a trusted BMW indy. Like you, I do 98% of my maintenance myself, but occasionally, I have a trusted source for advanced diagnostics when I get stumped.

[blah415]

unplug the actuator cable from the transfer case. see how it runs, if it runs fine, you need to start diagnosing there. buy yourself a c310 or c110 off ebay to read codes

[Chamberlin]

I'm driving my dad's 2007 X3 until I can get my 2007 E91 new headlights (a whole other nightmare).

My dad's X3 has most of the same symptoms as mentioned by the OP, aside from the low/no power situation on initial acceleration (that sounds flat out unsafe!). It does have the random hesitation, rough idle sometimes, and at stop lights it will buck forward; that feels just like when you forget to disengage the E-brake on a manual car and you try to take off... Rear end kinda squats under the load. Also has a CEL (I have codes on my Schwaben that I've cleared 4 times, but don't recal which code/module) and occasionally the 4x4 light will come on but is usually not a problem.

Planning on plugs, coils, transmission filter and fluid, Odometer Gears x-fer case gear.

We already did oil, filter, front diff oil, and the wonderfully expensive x-fer case fluid.

It sounds like we definitely need to inspect/ replace the hall effect sensors too... But which ones? The camshaft position sensor or crankshaft position sensor? I thought it was the camshaft sensor up on top of the valve cover that gets full of oil because of a bad seal? Or does the crankshaft sensor have the same problem?

[91e34M5]

I'm driving my dad's 2007 X3 until I can get my 2007 E91 new headlights (a whole other nightmare).

My dad's X3 has most of the same symptoms as mentioned by the OP, aside from the low/no power situation on initial acceleration (that sounds flat out unsafe!). It does have the random hesitation, rough idle sometimes, and at stop lights it will buck forward; that feels just like when you forget to disengage the E-brake on a manual car and you try to take off... Rear end kinda squats under the load. Also has a CEL (I have codes on my Schwaben that I've cleared 4 times, but don't recal which code/module) and occasionally the 4x4 light will come on but is usually not a problem.

Planning on plugs, coils, transmission filter and fluid, Odometer Gears x-fer case gear.

We already did oil, filter, front diff oil, and the wonderfully expensive x-fer case fluid.

It sounds like we definitely need to inspect/ replace the hall effect sensors too... But which ones? The camshaft position sensor or crankshaft position sensor? I thought it was the camshaft sensor up on top of the valve cover that gets full of oil because of a bad seal? Or does the crankshaft sensor have the same problem?

The crank sensor is on the side of the block near the starter. You should be getting a crank sensor specific trouble code if it is not sending good signals to the ECU. A bad crank sensor will cause issues with multiple control units in the vehicle.

[Sammy Po]

this is the same problem i seem to be having! crank sensor maybe i'll replace on tuesday when it goes to the mechanic....
the car does have a nasty oil leak too so i'm guessing it's dripping all over the sensor and making it throw codes.

[englishtom1596]

https://www.bimmerforums.com/forum/s...ue-and-surging

sounds very similar to the issues I was having.