99 Voyager low gear only and no reverse

My wife was driving our 3.3L 99 Grand Voyager down the freeway and it seemed to go into nutral. She pulled over and found it would not go into reverse and would only go a few feet in drive at 6 mph and then it would slip back into nutral. It would do this every time she turned off the engine and then started it back up. She found out that it would stay in low gear so she put it in low and managed to get off the freeway going 6 mph in low gear.

It drove up onto the tow dolley ok in low gear but it would not back off in reverse. There were no indications of problems before this.

This does not sound quite like the limp mode that is referred to in other posts. Does anyone have any idea what might be wrong?

Thanks.

that is the death of a solenoid pack when you go to shop probabilby replace tcm and solenoid pack frequenty dir or fauilty

Took it to the shop and they told me that if reverse is not working, it is a planitary gear problem. Had the transmission rebuilt. Shop said the spline shafts from the factory are not made of hardened steel. The after market ones they put back in are hardened steel. Why didn't they do it right the first time?