My 98 Sable transmission has suddenly started behaving strangely.  When
moving from Park to Drive, it seems to go into gear kind of harshly.  Then
when shifting from first to second, it's normal.  From second to third, it
doesn't slam into gear, but it does lurch enough to wobble your head
backward.  Then, on the highway I have no overdrive.  I was running about
2400 - 2500 RPM just at 45 miles an hour, and about 3100 RPM at 55 miles
per hour.  I drove home (38.5 miles) going only 40 miles an hour to keep
the RPM's around 2100.

This all happened suddenly, too.  It makes me think it's something
electronic -- maybe a TPS  or something.  Have you ever heard of this?

Oh, one other thing ... I parked on an incline with the nose down.  It
wasn't a particularly steep incline, but fairly significant.  When I went
back to put it in gear, it was hard to get back into gear and there was a
clunk noise.  It's what I've come to expect from this car and so when I
park on an incline, I normally leave the car in neutral and set the parking
brake very firmly, but I didn't think about it since I normally only have
the "clunk" problem when parking with the nose up.

Damaeus