[shorod]

I suggest you start by checking the level of the transmission fluid and confirm it is at the correct level. Being a bit under full or even a bit over full can cause symptoms such as you describe. The fluid should be checked with the transmission up to temperature, the vehicle on a level surface, and the engine idling with the transmission in Park. While you have the dipstick out (which I assume your '98 Avenger is old enough to have) visually confirm the transmission fluid is not dark like old engine oil and give it a sniff test. If it has a strong, unappealing odor, it's time to be replaced.

If the oil level is not correct, correct it before getting too excited about a major issue. If the fluid is dark or smelly, change the transmission fluid and filter. I would not recommend a transmission fluid flush as that could do more harm than good.

-Rod