Sorry for a late reply,  I finally took some vacation time.

Possible, and probably helped for a while, but usually what happens is a
portion of the fluid just drains out onto the ground.  When you again use
the OD, fluid again gets pushed past the internal O-rings and locks the OD
on but only partially.

Cure for solenoid is remove from OD, remove internals via the front of the
brass barrel, and replace the O-rings.  Size here is important.  Match at a
hydraulics supply shop.  Hardware or automotive rarely carry anything that
small.

Difficulty is, if the OD is locked on, after a while you would not have any
shudder since the fluid pressure would have built up to the pressures needed
to maintain full contact internal to the OD.  Usually around 25 to 30 MPH.
SInce your shudder is in all gears, the actuating pistons are allowing fluid
past and you are getting the shudder as the fluid is held and released past
those O-rings.

If this is the case,  your only "cure" is to remove the OD and change the
O-rings and actuating pistons.  I would surmise that you have the original
Teflon type O-rings which if not heated to around 600 F will fail into many
pieces after about  10,000 miles.  Rubber tyep O-rings that fit the Teflon
width groove do not have sufficient size to effectively prevent fluid blow
by which erodes the rubber to ineffective after about 5000 OD miles.

Duane