First you'll have to acquire a complete hyd
unit off from a 77 or 88, I believe the 770
and 880 are the same as well. Clean it up,
reseal, rebuild, check it over, etc. Check
the center plate of the actual hyd pump on
the bottom, they like to crack there do to
moisture accumulation and freezing.
Sometimes you can see the crack, sometimes
you can't. But the centerplates are
available, there is a poster here that goes
by "centerplate" that makes them. Also
check/replace bearings in pump body. You
need to have a PTO unit if you don't have
one. If you don't, get a PTO unit for a 77.
If you do, pull the drive shaft out of the
rear of the tractor by first taking off the
top cover where the handle goes in, by
removing the 4 small bolts just above the
actual splined PTO shaft. Once that it off,
remove the 3 bolts on the triangular cast
iron bearing retainer, use a prybar, and
pop the entire clutch pack and shaft out.
Much easier to handle than removing the 4
bigger bolts on the entire housing and
pulling the whole thing at once, but you
can if you like. Once that is done, you
need to remove the power lift (if it has
one), and transmission top cover, and off
to the RH side (as you would sit on the
seat), near the front of the transmission,
you will see a short splined shaft maybe a
foot or so long, with an approximately 3
inch or so gear held on with a retaining
ring. Remove that gear, and mark that shaft
right at the outside edge of that bearing
where the shaft passes through it and the
cast iron support. Make sure you mark it
after the bearing, so the bearing will
still support it. Cut it off flush with the
edge of the bearing, clean it up, reinstall
the shaft. Reinstall the trans top cover,
then install your hyd unit. Buy, or make
new gaskets for the top cover and the
bottom of the hyd unit. Reinstall the PTO
with a new gasket behind the 3 bolts
bearing retainer, reinstall the cast iron
PTO cover with the handle attached, being
sure to line up the forks inside attached
to the handle with the brass engagement
collar on the PTO clutch assembly. Fill hyd
unit with oil, attach new hoses and
couplers, and away you go. Please note, I
haven't done one of these for many years,
just going off memory. The shaft you have
to cut off may be longer or shorter than I
stated by a little, and the gear on the end
of it may be bigger or smaller than I
think. Also, if your tractor does not have
a power lift, it may not have the drive
gear or the longer shaft you have to cut
off. There should be a hollow looking area
around that bearing support when everything
is set up or ready for hydraulics. That is
the space the pump sets in when you put it
in place, the PTO runs the pump on the hyd
unit. I don't know for sure, but I would
presume that the later year 77 would be
more likely to not have the gear or long
shaft if it did not have a power lift from
factory.
Ross
