This was posted by Bill Schoening in 2006 in response to questions on rebuilding a flight pitch, or swapping for a variable pitch dynaflow:
Just a few comments about the Flite Pitch. As was noted I wrote several
articles on this transmission for the Buick Bugle (April 2003, I don't know the other dates - 58limited). I have overhauled
several and have one with 200,000 miles and still is fine.
First: This transmission must be overhauled using all the changes that
came out over the year. These changes correct the major problems with
it. If you can find a 59 service manual it has all the changes in it.
After the over haul and it is done correctly, it will out preform any
other Dynaflow. Parts are hard to find and in the messages Lemar Wilkins
was mentioned. He also knows these transmission and does a very
excellent job overhauling them. If any of you can find the Bugle
article I did, you will find some of the history and suggestion to keep
it running.
Second: The oils. This is a new problem and may cause ware and strange
behavior. The new Dexron III had many of the additive packages removed
that help on heat buildup in High contact areas. As the the oils
"IMPROVE""" this will get worse. I have switched the oil to the type
FA. For now this still have some of the additives that will help. So
those of you who are having some strange problems might consider making
this change.
Third: As some of you have noted to change from a Flite Pitch to a
variable Pitch or vis versa is a big deal. There are lot of changes
that must be made. I mentioned many of these in the articles. If you
want to have your big series Buicks from 59 to be correct they must have
the Flite Pitch. I have searched long a hard to find any official Buick
data that tells the dealers to change from the Flite Pitch. If any of
you can find official data I would like to have a copy.