I bought this van about 4K miles ago.
From the beginning when "starting" the starter had problems:
  1. 1 It would occasionally whir without engaging the flywheel, then suddenly drop into engagement
  2. 2 Upon prolonged cranking, it would jump out of engagement
Lately it did #1 without engaging consistently, until I had it out and a shop went through it .
They replaced the solenoid, but could find no other problem.

I thought maybe it was the wrong flywheel, but it has 132 teeth with a pressed on gear, so it seems to be the correct one.

could the starter gear be wrong? it has 9 teeth

Someone thought it could be out of alignment, but I think that's doubtful; the pins around two of the engine/trans bolts hold that alignment, and the starter is solidly in its hole.

Any thoughts would be appreciated; feel free to reply directly.

TIA