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

   / JD 4300: opening up the gearbox to repair broken PTO and range shift
  • Thread Starter
#21  
Any word on how the new Bobcat tractors are holding up?

The Bobcat CT335s purchased by the rental yard to replace the JDs are somewhat worse
for the wear. These units are substantially heavier and more robust than the JDs.

One that I saw had a serious dent in the rear steel fender. Several have been overheated while
mowing....one of them enough to blow the engine. They are being rented a lot for
rotary mowing, and the operators just don't seem to get that you have to clean the
rad screen often if you mow dead grass.

They bought a new engine from Kioti, since it was much less than Bobcat.
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift
  • Thread Starter
#22  
Before I filled the gearbox up with new tractor-hydraulic fluid, I cleaned the
inlet screen. To remove all the microscopic particles, I first used gasoline,
then I washed it carefully in a strong detergent, then I used an air gun to
dry it.

To get at the inlet screen, you have to partially remove the large steel
pump inlet tube below the tractor. I used this opportunity to closely
inspect the hyd pump inlet manifold. It is made of a soft plastic material,
and if it leaks, you will suck air into your hyd fluid. Bad.

Records show that this part has been replaced once already. I notice that
they arrive painted, perhaps to give them some protection from UV and
ozone.
 

Attachments

  • hyd_manifold.jpg
    hyd_manifold.jpg
    50.2 KB · Views: 311
  • hyd_manifold_2.jpg
    hyd_manifold_2.jpg
    70.7 KB · Views: 338
   / JD 4300: opening up the gearbox to repair broken PTO and range shift #23  
First I drained all the hydraulic oil and removed the inlet filter screen.
That leaves about a cup of oil in the bottom of the sump, so I
removed the PTO cover to clean that out and see what's in there.

It does not look good. I recognize the 4 brake engagement levers
on the right side of the first photo, apparently attracted to the
magnetic drain plug. Also broken pieces of the brake friction discs
are evident.

I lifted off the 3-pt housing and see why: the brake basket has
broken in half! All the engagement levers and their pins fell out
(second photo). One of the brake friction discs seems to have broken
up, but the others and the plates remain in place. The PTO clutch
looks OK.
Hopefully you're still around helping folks on this forum. I bought a JD 4200 that is stuck in A range, B and C range only gives me Neutral...
following these write-ups, I popped the PTO cover and took off the inlet filter screen underneath the tractor. There were very few shavings on the screen, and the bottom of the tranny housing revealed a broken shift fork as expected. There was no other debris in the housing. I expected to find brake parts and maybe pto clutch parts as both sides of the brakes stick and the pto clutch seems to be engage harshly.
My question is, do I have to remove the hydraulic lines on the top of the rockshaft housing to remove the housing, or can some of them stay on? TIA!
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift
  • Thread Starter
#24  
My question is, do I have to remove the hydraulic lines on the top of the rockshaft housing to remove the housing, or can some of them stay on?
You are going to have to remove the Power Beyond tube, but you do not need to take all the hoses off the AUX valve.

With the problems you have, I suspect you will need to change the plain bearing inserts inside the rockshaft pivots, too. When I bought these parts, they were available and reasonably priced from JD.

Good Luck.
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift #25  
You are going to have to remove the Power Beyond tube, but you do not need to take all the hoses off the AUX valve.

With the problems you have, I suspect you will need to change the plain bearing inserts inside the rockshaft pivots, too. When I bought these parts, they were available and reasonably priced from JD.

Good Luck.
Glad to see you're still around !
Ok, Thanks for the heads up. I need to look at the repair manual to find out what these bearings are, where they are, and where the AUX valve is so I can identify what you advised. It needs to warm a bit before I get back at the tractor, at or below 0 isn't conducive to tractor repair in an unheated shop..
Do you know if they changed the shift forks (made them stronger) mine is a 1999.
Anywhere to buy used shift forks?
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift
  • Thread Starter
#26  
Anywhere to buy used shift forks?
The forks may be repairable. You may want to contact a skilled TIG weldor/machinist.

On eBay right now is a listing in OH with most of the gearbox for sale. You might ask them to list the forks separately, as they have offered.
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift #27  
The forks may be repairable. You may want to contact a skilled TIG weldor/machinist.

On eBay right now is a listing in OH with most of the gearbox for sale. You might ask them to list the forks separately, as they have offered.
I think I saw the ebay listing that had all the gears and goodies, for just shy of $2k if it's the same one. Good idea asking them to separate.
I did think about welding - not something I could do, but maybe someone more experienced could....Appreciate the help!
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift
  • Thread Starter
#28  
If you look at my post #11, you can see the infamous range shift rod. If you look down inside the gearbox once you have removed the cover, you can see how the shifter fork is connected with a roll pin.

You can then use a long drift to pound out the roll pin. The shaft then slides out of the fork. If the shaft is broken at the O-ring groove, you have to grab onto it from the inside of the gearbox.

Dunno what happened to JPINCA. He has not been around in 5y. Losing your posted pix is why you don't want to use 3rd party hosts for these photos.
 
   / JD 4300: opening up the gearbox to repair broken PTO and range shift #29  
Yes, I was trying to get as much info as I could, with pictures, to better understand what I'm going to see once I get in there. It's still only 12 degrees here, so I'm not in a rush to get into the unheated garage to get the rockshaft cover off yet.
And for me, one of the shift forks themselves is broken and not the shift rod. I found the piece of the fork in the bottom of the housing when I took the pto cover off. it looks like it broke right where the rod portion of the fork would slide into the shifter? Will I be able to get to the forks for repair by removing the rockshaft cover alone?
Shift fork break.PNG
 
Last edited:
   / JD 4300: opening up the gearbox to repair broken PTO and range shift
  • Thread Starter
#30  
Will I be able to get to the forks for repair by removing the rockshaft cover alone?
You will need to get fork support body (16) off of shaft (21). I do not recall how that shaft can be slid out the side of the gearbox. I would have to look in the manual to see how. If you can, then no tractor splitting, even if you have to remove wheel, fender, and other stuff in the way.

If you can access that shaft from the outside, then remove the E-clip (22) and the detent (17) to free it up.

At least the shifter fork looks repairable. It also looks like a good candidate for 3-D scanning and printing with a durable material. I hear there are metals than can be 3D printed these days.
 

Tractor & Equipment Auctions

AGT Sawmill (A41856)
AGT Sawmill (A41856)
3149 1005NG GREAT PLAINS GRAIN DRILL (A35841)
3149 1005NG GREAT...
KPI 5036-25T Twin 36in. Sand Screw (A41660)
KPI 5036-25T Twin...
Mower King SSRC QA Brush Cutter (A41856)
Mower King SSRC QA...
2023 Ford F-150 XL (A39160)
2023 Ford F-150 XL...
2016 Nissan Rogue SUV (A39235)
2016 Nissan Rogue...
 
Top