JD 4300: opening up the gearbox to repair broken PTO and range shift

[dfkrug]

Here is where I am putting the new range shift shaft into the side
of the gearbox. You can see the infamous O-ring groove where it
breaks. This shaft has gotten pretty expensive, but it is hardened
steel. I am not against making one without the groove, but I think
if you don't force the lever, it will not usually break. Mine shifts
quite easily, when the gears are not loaded. I also put an O-ring
between the body of the bellcrank and the housing to keep water
from getting in there and making rust.

I have noted the PTO interlock switch, which eventually fails, keeping
you from starting the tractor. Mine failed shortly after I bought this
project. I have jumpered and soldered the wires and sealed then with
silicone (orange wires).

Starting the tractor with the PTO already engaged may actually be
desirable. It is also the most gentle you can possibly engage this
kind of PTO, essentially eliminating shock to the clutch pack.

 

[dfkrug]

Before I close up the hatch, here is a photo of the 3-pt cylinder.
Hema makes these by boring the cylinder right into the cast steel
of the housing. Some other tractors have a cylinder bolted or welded
in there.

 

[dfkrug]

Closed up and rusty patches cleaned & painted.

The green bit in the middle is a homemade dust cap for the load check
valve (JD now wants $15 for the plastic cap that often falls out).

You can see the new range shift bellcrank and linkage at the bottom of
the photo.

I have replaced the power beyond hardline between the AUX valves
and the 3-pt cylinder valve with a hose and QDs for a backhoe PB
loop. The inline filter, which looks like a fitting on the 3-pt cylinder
valve, had failed. I would not be surprised if most of these out there
are inoperative.

 

[scrappy isb67]

Starting the tractor with the PTO already engaged may actually be
desirable. It is also the most gentle you can possibly engage this
kind of PTO, essentially eliminating shock to the clutch pack.

Not necessarily, the hydraulic pressure might not be there immediately on startup and cause clutch pack slippage and uneccessary wear on the clutch pack.

 

[dfkrug]

Not necessarily, the hydraulic pressure might not be
there immediately on startup and cause clutch pack slippage and uneccessary
wear on the clutch pack.

The PTO clutch is a mechanically-engaged multi-plate wet clutch; no
hydraulic flow is involved.

 

[scrappy isb67]

The PTO clutch is a mechanically-engaged multi-plate wet clutch; no
hydraulic flow is involved.

then why can't it be feathered in? there is little to no shock unlike a hydraulicly engaged wet clutch that my 2320 uses

 

[kennyd]

then why can't it be feathered in? there is little to no shock unlike a hydraulicly engaged wet clutch that my 2320 uses

Are you thinking of the 4x10 series? The 4300 has a lever to engage the PTO-not a switch.

 

[scrappy isb67]

Are you thinking of the 4x10 series? The 4300 has a lever to engage the PTO-not a switch.

I WAS thinking it was electrohydraulic until I was corrected.

 

[dfkrug]

then why can't it be feathered in? there is little to
no shock unlike a hydraulicly engaged wet clutch that my 2320 uses

The PTO engagement lever uses a fork to push against springs on a shaft,
until it reaches a mid-point, where the springs take over and the clutch
plates are engaged rapidly. No feathering possible. Totally unlike
engaging a dry foot clutch.

I do not know how the PTO clutch/brake works on the 2x20s, or other PTO
systems that use an electric switch to engage/disengage. I suspect that
a solenoid is used internally to operate a lever that then works
in a similar way to the 4x00s. I know that JD lawn tractors use an all-
electric external clutch; bigger tractors use wet multi-plate clutches/brakes.
I suspect that all wet clutch PTO systems employ a PTO brake (unlike
dry clutch systems) due to the inherent drag of an unengaged wet clutch.

 

[jpinca]

Most of the 4300s were rented with tillers, but when they were first purchased the
rental yard still offered 3-pt mowers and box blades. Those were sold off years
ago.

Breaking the PTO brake running a tiller just shows that turning the PTO on and
off at full RPM was often done by renters. The previous group of tractors also
suffered many PTO breakdowns (JD 955).

The fact that most have held up at all is a testament to their toughness.

Any word on how the new Bobcat tractors are holding up? They look much heavier than the JDs, but the stats seem about the same.