For the past 2 years I have owned a 2002 Jeep Grand Cherokee 4.0L 2WD and it has a little over 130k miles on it. Today I got into it and placed it in reverse to go to the grocery store and pressed the gas and it didn't move. The engine reved, but it didn't move. I put it in drive and it pulled forward just fine. I turned it off, and turned it back on and it did the same thing. I drove to the store and is seemed to shift through the different gears just fine. I only went about 35 so I probably didn't get out of 3rd. When I got home, I noticed a slight odor. Smelled kind of like clutch, but it was very brief and was gone before I could be certain.
A little history on the vehicle: My driveway is sloped and occasionally when shifting from park to reverse it will make a clank, as if something was falling into place. Once or twice I have been unable to shift from park to reverse and had to turn the car off and back on before it would do so, however this has not happened in several months. A week ago, I was driving down a steep mountain (7% grade) and turned off my overdrive so that I wouldn't roll to quickly and I again got a clank when it down shifted (was driving appx 60 mph). Over the past week, I have felt a little shimmy when the RPM's get up higher prior to shifting from 1st to 2nd and then from 2nd to 3rd, however the shifting itself is smooth, with no noticeable slippage.
My question is does this sound like a solenoid, a Governor Pressure Sensor (which I hear is pretty unreliable in my particular vehicle), or do you think I may need the transmission rebuilt?