[TR] Weird J-type OD symptoms

[tr3driver at ca.rr.com]

The J-type on my Stag has been working great, but has just recently
developed some odd symptoms.  The most telling version I think : Was fine
for perhaps 20 minutes of stop-n-go surface street driving (with OD switch
off).  But after maybe 5 miles at freeway speeds (switch still off), it
started trying to engage.  Not firmly as usual, but like pressure was slowly
building to almost enough to shift.  

When I first felt the drag on the motor, I let off the throttle and the
engine rpm dropped back to OD levels.  Stepped on the gas again and could
feel the OD clutch slip, so I flipped the switch on (which caused it to
engage firmly).  But then when I got off the freeway, it stayed engaged
and/or partly engaged even in 1st and 2nd gear and with the switch turned
back off.

Going over how this thing works in my head, it seems to me that the solenoid
must be leaking fluid into the dashpot that controls the relief valve.
Could be the valve head (inside the solenoid) has come loose, or perhaps the
return spring inside is broken, maybe even the plug in the end has fallen
out; but has to be inside the solenoid.  Even a leaking O-ring on the
outside wouldn't do it, because that would still leave the dashpot passage
open to the drain.

I originally thought it might be the dashpot hanging up (since the first
symptoms I noticed were that it would not disengage when it should), but
this morning's experiment seems to disprove that theory (as it was firmly in
direct drive then shifted all on it's own).

Has anyone else seen this problem, or have alternate theories about the
solution?  If memory serves, I have to drop the rear motor mount to unscrew
the solenoid, so I'll probably tackle that tomorrow.

PS, another theory : If the 'idle' pressure (normally about 20 psi) was too
high, could that blow the solenoid valve off it's seat and cause these
symptoms?  I shimmed it up to about 30 psi when I had the unit apart, which
perhaps was a bad idea (trying to get it to shift faster).

-- Randall