2001 QX4 shifting problems...advice needed please

[brushnfloss05]

Hi all QX4 experts...Have a 2001 QX4 with 116,000 miles. Past few weeks has been doing some crazy shifting-but not all the time. My mechanic is stumped...no transmission codes showing. downright scary when driving in the colorado mountains!Example 1: when pulling out from a stop into fast moving traffic, RPM's will jump up to 5 or 6 and SUV will not accelerate very fast or shift. Eventually if I lift my foot off the gas pedal, it will shift.Example 2: when driving around 50 or 60 MPH, and need to pass or accelerate to get up a hill, SUV will not shift up. You can feel where it needs to shift (slight pause), then RPM's will just continue to go up with no shifting. Again, if I lift my foot off gas pedal it will shift (eventually).Have had this vehicle for 30,000 miles, never done a transmission service. Do you think this might help? Any advice greatly appreciated.

[qship96]

Time for a $3000 new transmission.