My transmission has developed an overdrive problem
that seems more serious than the relay/solenoid problems
described in the FAQ.

This winter the overdrive stopped working, unless I let the car idle
for about 15 min prior to driving. If I did that, the
transmission seemed to shift normally. If I didn't warm it up
this way, after 15 min of highway driving it sometimes shifted
into overdrive, but not reliably.

I've changed the relay (no effect) and now the solenoid with a used one. This
has changed the shifting, so that now with no warm up, it will shift
into overdrive by my first accerlating hard (foot to the floor) above
50 or 55 mph, then letting my foot sharply off the gas. If I slow down,
the car will shift out of overdrive at about 45 mph. This seems like
a kickdown problem, but I've tried fiddling with the kickdown adjustments
both ways to no effect. Other up shifts, downshifts and kickdowns seem normal.

Anybody got any ideas what gives? When the trouble began, the trans was
about 3/4 pint low on fluid, topping it off had no effect (small leak at
pan gasket).

Thanks!