Tractor Repair: Repairing 4wd Clutch on Case Mx120, clutch discs, infinite resistance

Question
Hi William,

We have a problem with a Case Mx120 on which the 4wd will not disengage, we have looked at all electrical elements so have concluded that the problem must be either:

1. Loss of hydraulic pressure somewhere on 4wd circuit
2. Failure of 4wd clutch

Do you think we might be missing something else?

Would you happen to know where on the back valve block we can check the pressure on the 4wd circuit, and what pressure we should be getting there?

If it is the 4wd clutch that has failed, how big of a job is it to repair/replace?
Where do we split the tractor to gain access to the 4wd clutch?

Many thanks in advance.

Kind Regards,
Darren

Answer
not sure which port is for the 4wd you have 4 solenoids on the back valve block fwd rev 4wd and a modulation solenoid for easing in gears I've only ever tested the fwd and rev as far as i know the test ports have fwd and rev printed alongside them so look for a similar port that might have some indication printed i think the modulation port has mod printed alongside it
if the solenoid is getting power and the solenoid is ok then your on the wright track
you can test the solenoid with a voltmeter set to ohms check the resistance in the coil at a guess it should be somewhere between 3 and 8 ohms if much lower than 3 and it would blow fuses
if you get 1 meaning infinite resistance then the solenoid is gone replace it
test the pressure should be somewhere between 16 and 19 bar after that you could check the spool to see if there is dirt or that its stuck
there is a good chance the 4wd clutch discs are bad and a piece of one is jamming them all together or they are warped
to remove the 4wd clutch you need to split the tractor under the cab just a bit behind the hydraulic pump there is a plate in the floor of the cab that can be removed to make taking off some pipes etc easier
the 4wd clutch is at the bottom of the gearbox and will stay with the back end when you split
I'm not 100% certain but you might have to take off the sandwich plate to get the pack out(i think there might be a circlip holding the 4wd clutch at the back but i cant remember for certain# if so watch all shims as they need to be put back in the same places for each bearing there is a special silicone#case dealer will have it think its locktite 512 or something) used for re joining these gearboxes do not use normal instant gasket as it messes up the preload on the bearings
the sandwich plate is fairly heavy so i made bars that would thread into two of the holes on top rest the bars on a drum at the front and slide it out on the bars
if you do have take off this plate put twine on the oil pipe behind it before you put it back together so you can line them up as you put it back
these tractors can be hard to put back together as you have to line up 3 shafts
but if you remove the plate on the right hand side of the front gearbox inside is the creeper reduction gears loosen the locking nut on the shaft.count threads as you do it then remove circlip and you can take the shaft out until the tractor is joined now you can turn the different shafts so you can line them up
let me know how you get on i hope you don't have to go this far