[AT] N hyd lift rebuild

[Chris Britton]

R&R of the lift cover and the hydro pump for an 8n ( 'bout the same for a 
9n/2n ) can be done in about 9 hours, casual working.

Chances are, the 'weakness' in your lift is the lift cover.. not the pump. 
Check it.  pull the round inspection cover with the dipstick in it, right 
side.. look in there with a flashlight, on one of those warm days with a 
heavy load on the lift.  look for leaks.  most of the leaks are from the cyl 
mouth.. Other areas for leaks can be from between t he cyl and top cover, 
top cover to center section at the right front corener where the hyd 
standpipe is... the standpipe itself in the center section, pump/bottom 
plate to center section at the right front corner, again.. where the 
standpipe is.  from there, the next easiest to fix leak is the pressure 
relief valve.. it is situated in the back of the pump ( towards rear of 
tractor ) and will be seen as a swirling in the oil.  If the puimp itself 
has problems, look for leaks on the chamber gaskets, and the pipe plugs on 
top.

I f the leak is strictly inthe top cover.. the r&r time drops to about 4 
hours.

If the cyl leaks.. I suggest either getting a new cyl and reuse your old 
piston.. but get a new ring set ( about 100$ ).. or hone the old cyl and get 
a new NAA piston, and oring, and leather backup washer.. ( 28$ .. assuming 
the hyd cyl can be honed smooth enough to not cut the oring..)
Usually small scratches.. aren't a problem, once you hone.

To remove the top cover... remove seat and spring, remove 3pt lift link arms 
at the knuckle from the upper lift arms... might take some pb blaster.. a 
plumbers torch.. and a mallet and drift, and patience.  Remove the bolts 
fromthe lift cover on the perimeter only.. do not remove the bolts inthe 
center of the cover.. they hold the cyl to the underside of top cover.

(Make sure you have an 8n top cover, and not a 9n top cover.. 9n/2n top 
covers have a control fork which needs to be spread from around the "T" 
control valve on the pump.)

Now. if the top cover is stuck on, get a floor jack ( bottle jack ) and a 
piece of 2x4.. put the 2x4 under a lift arm where it joins the top cover, 
and apply a little 'up' pressure with the jack... should pop it loose.  if 
it needs help, take a gasket scraper and tap it into the gasket area... 
really try to avoid that as you don't want to mar the surface near the 
pressure port.

top cover weighs 80# so be ready.

flip it over on a bench, pull the bolts holding the piston/cyl assy.. use an 
air nozzle with a rubber end and put a little air to the hyd port inthe top 
cover and the hyd piston pops out in your hand.. observe orientation of 
piston and how the dogbone fits in it,

Replace the cam follower pin.. it is a small metal dowel rod.. use a small 
socket to backup the linkage and drive the pin out.. drive new one in.  if 
it isn't appreciably worn.. don't mess with it.

Be aware that 3 small  sized gaskets go between the cyl and top cover and 
are essential.

Either rering the piston, or get the NAA piston.  Set naa piston on a 
table..  bogbone end up.  Oring on first.. then backup washer.  Rough side 
of leather washer to the oring.. flat side of leather washer to the piston. 
If you use the neophrene washer from CNH.. it is cup shaped so is obvious. 
Make sure the orientation, as you want hydraulic pressure pressing the oring 
into the washer.. not the other way.. and dogbone faces out to push the lift 
linkage.  Boil a pot of water.. take off burner.. drop the leather washer 
inthe pot.. let set 15 minutes.. take (2) dinner spoons and use them to get 
the washer down.. the spoons work with the oring too..  Lube with trans 
oil.. cooking oil.. crisco.. whatever to help oring/washer slide into 
place.. then lube piston assy again and slide into cyl mouth.. oring will be 
proud.. use those spoons again to compressit all the way around as you slip 
it in... bolt back up.  use a gasket scraper and carb cleaner to get the 
gasket surface shiny eat-off-it clean.. both on the top cover.. and the 
center section.  BE SUPER CAREFUL around the right front corner pressure 
port.. don't mar the metal.  DO use the CNH or Tisco paper top cover 
gasket.. don't use any gasket goop at all.  Lay the gasket out overnight 
under a book to make it flat.  If it won't stick flat.. use a couple dabs of 
chassie grease to stick it down in a few spots.

Have a helper or a third arm and an extra eye help you reinstall the top 
cover.  The control arm must be inserted in the small control valve yoke in 
the front of the hydro pump.  As you lower it down.. even a child can guide 
the small arm into place.. no weight.. not hard.. just precision needed.

Reinstall bolts... torque and reinstall 3pt linkage and seat/spring.  ( 
torque value is inthe I&T fo-4 manual.. number escapes me at the moment... 
this procedure is also explained in the fo4.. though it leaves out a few 
'hardship' issues.

Now.. for pump R&R

drain hydro fluid.. all 3 drains.

trans in neutral, clutche blocked, wheels chocked engage pto

remove 4 bolts from pto flange bearing carrier.  Slide pto shaft out.  have 
a piece of newspaper ready to rest it on.  If pto bearing is good ( no shaft 
play ) and seal is good... set it aside for reinstall.

If it binds coming out spin shaft a bit while pulling.  Slide a screwdriver 
thru pto shaft hole for extra leverage.  Use a copper/brass maul to tap at 
flange to try to get to rotate.  Once flange clears housing.. shaft should 
slide out under hand pressure.. if it binds bad.. the transmission side 
splines on the pto shaft may be twisted from yers of use with no orc. 
Sometimes a little tapping brings it out.. sometimes loosening up bottom 
pump bolts helps.  in extreme cases, you slide it back in, and then use a 
saszall to cut the shaft before and aft of the pump, drop the pump, and 
drive the slug out o fthe pump carefully, then pull the splined end from the 
pto coupler.

Assuming the pto shaft comes out fine, then put a floor jack under the pump 
with a piece of wood inbetween.. remove bolts. it should drop out.. if not.. 
apply pressure with that 2x4 thru inspection hole to top of pump.. or use 
the gasket scraper.. again.. be carefull to not mar the mating surfaces.
Alternately.. if you are meduim+ build.. you can lay under it and drop it to 
your chest.. then manhandle it.  In any case have extra newspaper out.. when 
the pump drops.. you get the last 3 qts of the 5 gallons of oil out that 
don't come out the drain...

>From there, r&r is pretty much bolt for bolt.  most of the time.. unless the 
pump chamber gaskets leaked.. i don't touch the pump.  I do however remove 
the spark plug sized/shaped relief valve, and install a new one ( 28$ 
cheap )

Clean mating surfaces.. and hose out the sump.. mineral spirits or diesel 
work great.. also thins and helps clean up all that oil you just dropped on 
your wifes carport...

Reinstall opposite of removal.. make sure control arm lines up in control 
valve.

Now.. her eis the kicker.. Mostly these old tractors are loose tolerance 
machines.. however... some joker who made the hydro pump fit in the center 
section made it a 'perfect' fit.  If the pump won't slide up and in.. tilt 
the back of the pump up at a .. uh.. 1' angle and it should go in... again.. 
use the paper gasket and no goo.  reinstall bolts.. torque. .  Pump base 
weighs about 80# too.. depending on if you have the iron pase plate or the 
aluminum base plate some pumps had.

If pto shaft was good.. clean gasket surfaces and reinstall with 
papergasket.. no goo... torque

Twist the pto shaft as you reinstall it.

Now reinstall side cover.. clean gasket surface.  Now here.. you can use the 
25 cent paper gasket.. or any gasket goo you want..  won't make a 
difference.

refill with 5g of oil.. either 90wt gl-1/3 or if you prefer the thinner 
stuff... UTF.

If pto shaft has loose bearing or bad seal.. either replace bearing and 
seal.. or get a new assembly for 99$.  Seal / bearing isn't a huge bear.. 
but if the pto shaft is the old style and you are not 'restoring a parade 
tractor'.. or if there is any wear on the splines.. just get the new 1 3/8 
unit and save the time of removing the retainer clip  and then pounding the 
pto shaft end on a block of wood till the flnge falls off so you can get at 
the bearing.. etc..


I think I covered most of that...

Wheel seals... that's a nother book... I'll let someone esle tackle that 
one.. my fingers are tired.  I will add.. that if yo have a late model with 
outter and inner.. you are gonna have better sealing.. etc.

To 'help' the oil leak.. only fill with oil till oil dribble sout the bottom 
hole on that round cover.  That's less than the 5g.. but is plenty of oil. 
The diffy and tranny are imersed enough to pickup and sling the oil.. and 
the pump inlet is at the lowest point in the sump... that keeps oil from 
pooling at the mouth of the axle trumpets, and off the tranny input shaft 
seal.

Soundguy


>From: "Ken Knierim" <ken.knierim at gmail.com>
>Subject: Re: [AT] tranny fluids
>Now that I have an 8N in AZ, I can tell when it gets hot because the
>lift won't pick up the mower on the back very well (revving the engine
>helps). There's been some good information here about what I need to
>do to fix it when/if I ever get it apart. My question is: how hard
>will it be to get the pump out and rebuild it? And is there anything
>that can be done to stop the oil from leaking onto the brakes? Every
>N-series I've been on had little or no brakes.
>Ken in AZ