1st gear is engaged by shifting into L at a full stop or by flooring the
accelerator at low speed. So one stops, shifts into L - starts off,
shifts up to S and immediately back to L to hold 2nd gear, then shifts
up to S for 3rd, then to D for 4th.

Your car idles in and starts off in 2nd gear by default; that's so it
doesn't creep at idle while waiting for traffic etc. The newer models
idle in 2nd but immediately down shift to 1st upon a press of the
accelerator.

Shift Quality: The transmission has a vacuum powered shift modulator
that's designed to provide soft shifts on light throttle and harsh
shifts - no modulation - at full throttle acceleration.

The MORE vacuum at the modulator the SOFTER the shift. So a vacuum leak
from a broken or disconnected vacuum line will result in hard shifts.
Start at the transmission's right side look for the modulator and a
plastic vacuum line attached to it, follow the line up to the engine.

Shift Points: The transmission is "told" the throttle position by a rod,
cable or vacuum line - I don't know which your model uses - so the
transmission will "know" when to shift appropriately. Take a look at the
throttle linkage to see if there's a rod or cable down to the right side
of the transmission. If so, come back and I'll tell you how to check its
adjustment.

Change your fluid and filter to see if the condition improves... but most
likely to be the modulator too.

After reading the posts to the original question I'm wondering if the
modulator could be causing the really harsh shifts I get from 3rd to 4th and
back under moderate to fast acceleration.  Doesn't seem to be a problem
under full acceleration.

If the hose were off or the modulator had failed completly would the car not
shift at all?  Also, I see that it's less than $40 at Autohaus and wonder if
it's difficult to replace.

Thanks,

Mike