'95 jeep wrangler 4cyl , 4wd, auto

Hi Guys,

This car has 142k miles.

The car starts fine

On the road, the engine gains speed, but the engine (or trans ? …i dunno))is pulsing, or slipping and now the tach needle is dancing up & down

This has been going on about 3 weeks

Appreciate any help here

Thanx,