I now have a very different read on the causes of these gear problems thanks to helpful comments from fellow Listers.

Please recall that my gear trouble was that the nose gear had retracted onto an already closed gear door.  A number of Listers suggested it might be caused by "trash" in the hydraulic line which could interrupt the ordinary flow of fluids and pressures.  Perhaps this was true because I repeated the gear retraction onto a closed nose gear door when on the jacks.  Still later (about 10 cycles of the gear), a hose in the right wheel well burst causing total lose of fluids and pressure while on the jacks.  Previous to this messy event, I observed that the diameter of the 2000 psi hoses was measurably larger than when unpressurized.  Further, the outside rubber coverings of these 303-type hoses were badly cracked revealing only a fiberglass reinforcement of the interior rubber (or Teflon??).  In short, the hoses were shot and in need of replacement.

All hoses (14 total) now been replaced and I can announce that the learning curve has again been confirmed here in Texas.  The first hose took me about an hour and a lot of grunting to complete.  The second took about 35 minutes and the last four which were blemish free took only 9 to 12 minutes each.  The new 303 hoses are double wrapped in SS mesh that render a 3000 psi rating.   New hoses, new -4 fittings and, new hydraulic fluid all for a price under $300.

My original hoses were installed in 1992.  If your 235, 320 or 360 is about the same age, consider replacing all fittings, hoses and hydraulic fluid.  Doing so may avoid for you much of the gear trouble we have recently been hearing about.

Tips:  Use a long, tapered have-inch punch and cut the SS hoses smoothly and cleanly with a Dremel tool metal cut-off wheel (not mentioned by the manufacturer).

Many thanks to those who helped me analyze this problem.

Greg Nelson