[AT] Tractor Fluid (OT, only maybe)

[Stephen Offiler]

I've got a 1991 Ford 1520, a Japanese-built 23HP diesel 4x4 hydrostatic
from approx 1991, just before Ford sold to New Holland.  A few weeks ago I
did a 1000-hr major maintenance including hydraulic fluid change.  I've got
the original service manual, which calls for "Ford 134" fluid.  The only
other reference in the manual is to Ford part numbers 1GM-134C (1 gal) and
5GM-134C (5 gal).  Searching around the net, I concluded this stuff must be
Ford M2C134x fluid where the x is like a revision, starting with A which
apparently was used in the 8N era... hence, this really isn't all that OT
after all.  Looks like they were up to rev C in the early 1990's based on
what is called out in my manual, and it also looks like the modern standard
is up to D now.  If I got any of that wrong PLEASE jump in.

I ended up purchasing Coastal 303 Tractor Fluid, which I was a bit leery
about, until the sales guy pulled out a multi-page document from behind the
counter that listed a wealth of detail on Coastal 303, including
compatibility with the Ford M2C134D spec.  OK then, sold.

The problem I am having now is that the fluid seems too viscous.  As the
cold weather arrived, I immediately noticed that the loader lifted slowly
and the bucket roll was almost ridiculously slow.  Not long after that, it
literally blew the gasket off the hydrostatic filter.  My first clue was
copious amounts of fluid pouring from the filter area, and once I removed
it, I observed the gasket was out of place.  I tucked it back in, tightened
the filter up real good, and it was OK for another couple weeks.  Just
today, same thing, it's pouring out the filter gasket again.  I am
concluding that the fluid is too thick, the flow is too slow, building
pressure on the return side (filter side), and that's what is blowing the
gasket.

If I got all this right, that means Coastal 303 is NOT so very equivalent
to Ford M2C134D after all.  Does anybody have any knowledge of these
fluids?  What do I really need to be shopping for?  (I don't know where or
IF I could even find genuine Ford fluid any more)

Thanks in advance.
Steve O.