The transmission warning red light on my Isuzu Trooper 1995 started
flashing and only the "R" and "L" shifts in 2 WD function. All the
other gears in 2WD and 4WD either won't move the car forward or are
too sluggish, similar to a disengaged clutch in a manual stickshift
transmission. I tried filling up the fluid but it dodn't do any good.

Any thoughts/suggestions before I have it towed away for an almost
expensive checkup/repair bill will be appreciated. Thanks!