88 300E auto transmission problem
 

It is an 88 gasoline 300E, straight 6 cyl. auto trans, and it is
getting more difficult to get into high gear.
I sometimes can hit the passing gear and it will upshift, after a surge
forward for a few hundred feet, great going then, when it does upshift
to high gear. but mostly it likes to run in the lower third gear. When
I shift to neutral and back to drive say at fifty miles per hour, it
will go to high gear, but immediately downshifts to third gear.
Sometimes in third gear it will start slipping, engine over revs,
perhaps when it is trying to upshift and I must slow down to twenty
thirty MPH and off we go again in third gear. I had the fluid and
filter changed and it did not help, the old oil had a burned smell as
well. the transmission has over two hundred thousand miles. Is it time
for another tranny? Is this old car worth
thousand twelve hundred for a good used tranny? The gasoline motor
runs like a singer sewing machine, not sure that term is used anymore,
but it used to be a valid statement.
kind regards
david