Lloyd E. Sponenburgh wrote:
Reach 50mph, RPM==1350, hold steady speed.
RPM's slowly increase over 5-10 sec. to 1550
_GENTLE_ addition of throttle receives drop in rpm to 1350
and firm feel of converter lock again.
Lift back to steady speed, rpms drift back up to 1550.

Above 62mph, lock seems to hold at steady speed.

This is just BACKWARDS from what I'd expect to see. Anybody have any
experience with the beast that can help me figure it out?

I think that "slide" out of lock is dangerous to the converter clutch.

I haven't installed lights on the shift and lock solenoids yet... guess
that's next.
There usually is a pressure test port on the transmission, where
you can rig a pressure gauge. Either use an electric pressure
sender or make DARN sure the lines are very secure and can
handle several hundred PSI of hot oil. You sure don't want
something letting go and spraying you with oil at 100+ C while
you're trying to stay on the road at 55 MPH. Some
transmissions, at least in the old hydro-mechanical days,
changed the pressure relief valve setting for different modes.
I'm not sure they do that anymore, except maybe for reverse.

I haven't had a car that did the converter lock-up in anything
but highest gear, but they are all different. And, usually the
lock-up is at about 45 MPH, after you've held steady throttle
for a few seconds.

It is also possible that this is a computer or engine sensor
problem. (Oh, yeah, the standard "Car Talk" show question "Oh,
by the way, is the Check Engine light on?")

Finally, some (maybe all) transmissions are designed with
extremely marginal grip on the clutches, to get that smooth
slide into gear. If the wrong transmission fluid is used, they
may never lock up properly when they are supposed to. I think
my wife may have killed her tranny a few years ago, when
somebody told her to add transmission fluid at a gas station.
It took a $1300 rebuild the next week. Of course, they may have
been right, the tranny was already sick, and the fluid really
had nothing to do with it. I'd guess a rebuilder would know to
put the right stuff in there.

I do agree with you that if this slipping in and out of
converter lock-up is not being commanded by the computer, then
you have a real problem. It is not as bad as another clutch
slipping, since the converter still carries some of the torque
(unless this one drains the converter on lock-up, some do) but
it is a sign something major is wrong. If it is being commanded
by the computer, it may be a quirk of the drive-train management
software, and may be fully intentional to keep the engine out of
a specific RPM range or some other oddity they wanted to do.

Jon