new holland TD75da 4wd does not disengage properly

[RickB]

Many of the farm tractors use hydraulics to disengage the front axle drive clutches.
To engage the front drive a solenoid dumps the hydraulic pressure off the clutch pack,
which lets the multi-disk wet clutch put the power to the front wheels.
Many of them when both brake pedals are applied ( some above a certain speed) will automatically engage the 4 wd to provide 4 wheel braking.
If you unlock your pedals and apply just one brake you most likely will not see the 4wd engage light.
If yours is taking so long to disengage I would believe that you have a restriction in the porting going to the solenoid actuator or a leak in the internal system.
It is also designed to engage when the engine is off.

Exactly how this system functions. The icon lights in the presence of keyed power and the absence of pressure between the solenoid valve and clutch. The OP has not said whether he is relying on the icon or has actually verified 4WD function. The most common failure in this system is the pressure switch. His could be failing, or there may be another problem that does affect 4WD operation.

 

[rackmaster2]

Exactly how this system functions. The icon lights in the presence of keyed power and the absence of pressure between the solenoid valve and clutch. The OP has not said whether he is relying on the icon or has actually verified 4WD function. The most common failure in this system is the pressure switch. His could be failing, or there may be another problem that does affect 4WD operation.

I had to leave the post, have a grandbaby on the way , not here yet.
when ICON is on , it is in 4wd,
when switch is in 2wd, icon stays on for several minutes and unit stays in 4wd for some time, i can feel it release when it finally goes to 2wd. and icon will disappear.
when it finally goes to 2wd and i shut engine down, when it is restarted , the icon is on and it is in 4wd, even tho the switch remained in 2wd.

 

[Agvg]

And it remains on after start and does not disengage after the same amount of time like it does when you disengage it with the switch?

 

[rackmaster2]

And it remains on after start and does not disengage after the same amount of time like it does when you disengage it with the switch?

Yes , it stayed on Simuliar to how it does when idisengage with switch.

I also checked the braking ,
Just one pedal depressed, no icon
Depress both petals same time , icon on dash appears

 

[LouNY]

So it is functioning properly for engaging the the 4wd,
it is not disengaging quickly, for some reason you are not building pressure in the unlock mode.
The solenoid may be failing, not opening fully or there is a restriction in the flow to it,
or the clutch pack actuator has an internal leak.

 

[rackmaster2]

Thanks guys, been involved with a new grand child recently, so have not been back on site.
What is crazy is that the next time I got on it, it worked proper, I engaged it and disengaged it several times, I had been using the tractor about an hour. checked braking , and it was proper, hit both brakes, icon would show, hit just one brake , it would not. So, Im thinking maybe it was just acting up since it had not been used in a while.

But, ive been back on it for short periods of time since and its remained locked into 4wd. Ive switched it back and forth several times, reversed direction on the tractor etc, but still stays in 4wd. (icon shows) would not be a big concern but I do have to put on blacktop sometimes to travel between fields.

So, what would you recommend to do first?
1- replace rocker switch ?
2- solenoid? ( not sure where it is located I dont have a book on it)
or take to NH ? not sure I have the skill set to replace or repair clutch pac actuator.