2004 X3 manual-xmission w/problems

[dj_2latino]

Greetings,
My '04 X3 is having major transmission problems after 83,000 miles. Anyone having this problem?
At 83K miles I began having hard slips and jerks in the engine/transmission while shifting gears. Now at 86K miles the problem has gotten worse. I took it in to the dealer and $475 later, they handed it back to me with absolutely no idea what was wrong with it. They called me three times to request more labor hours to continue "looking" for a cause. I went from $70 to $125 to $475 and the next request was to $580. This is what was done so far:
1) They ran a diagnostic check and found no errors.
2) They inspected the motor mounts and found them to be fully intact.
3) They drained the transmission fluid and found no metal shavings.
4) At this point, they made the call to request to drain the transfer case and look for metal shavings there as well.
I declined further inspection because I felt they were slowly trying to raise the price on me just for an "inspection" not to include the cost for the final fix action.
I took the X3 home and did the transfer case flush myself and found no metal shavings there either. Had I authorized this attempt, the next call probably would have been, "Nope. That wasn't it either sir. Can you authorize more labor hours so we can take the wheels off and look there as well? (Suckerrrr)"
Does any of this sound familiar to anyone? I still have no idea what is causing the jerks and slips between gears. Any recommendations?