Traction 4200 Hydrostatic positive lock won't engage completely

[simonds]

1999 JD 4200 hydrostatic. Positive lock differential petal won't lock in completely. I can feel it going in and out while holding the petal down. I don't find any adjustment on it. Any help out there? Thank you.

 

[beenthere]

Look at the linkage on jdparts.com and see if you can decipher where the problem might lie. Might be something broken.

 

[kennyd]

Here are the two breakdowns from JDP, if you can "feel it going in and out" then I'm afraid it might be internal.:

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[simonds]

Thank you for the replies. I'll check it out further.

 

[texasranger556]

I just started tearing into my 4300 to fix the diff lock. I bought it that way and from what I'm told the lock itself is a cast piece which is prone to breaking if engaged after one wheel is already spinning. A school had used it to plow sidewalks so it probably did a fair bit of spinning if the new guy forgot to engage 4x4. The pedal moves fine but doesn't do anything. The part is between $100-150 from memory, but lots of hours to replace it. According to the manual have to remove the right final drive and the 3 point rock shaft assembly. Hoping to get the old one remove this weekend, can let you know how it goes.

 

[dfkrug]

One side of the diff-lock mechanism is soft cast steel; the other is harder/tougher steel.
So the former wears a lot when rubbing against the latter. If there is enough meat left
on the cast part, then you can shape it with a grinder to make it grab better, as I
did for one of my 4300s.

Otherwise, you are gonna have to buy the whole ring and pinion set. $$$$

 

[texasranger556]

One side of the diff-lock mechanism is soft cast steel; the other is harder/tougher steel.
So the former wears a lot when rubbing against the latter. If there is enough meat left
on the cast part, then you can shape it with a grinder to make it grab better, as I
did for one of my 4300s.

Otherwise, you are gonna have to buy the whole ring and pinion set. $$$$

Wow, great pics! I'm assuming you're holding a new piece in the second pic? What did the original one look like?

 

[dfkrug]

Wow, great pics! I'm assuming you're holding a new piece in the
second pic? What did the original one look like?

That IS the original piece. I just reshaped it with a die grinder and an angle grinder.

 

[texasranger556]

That IS the original piece. I just reshaped it with a die grinder and an angle grinder.

I mean the smaller piece in your hand in pic 2 (not with the arrow), it looks like you ground the ring/pinion side.

 

[dfkrug]

I mean the smaller piece in your hand in pic 2 (not with the arrow),
it looks like you ground the ring/pinion side.

Yes. Only the part attached to the ring gear was reshaped. It was an error on JD's part to use
such a soft steel as part of the diff-lock dog clutch.

It seems to work OK after this repair. No new parts were purchased.

 

[beenthere]

What is a good way to test if the posi-lock is working?

I've never felt good about using it on my 4300, as have been too nervous about breaking something in the process. Also, never really knew that both wheels were locked in, as tough to see the wheels spinning (or not) when hidden be the fenders.
Usually if one wheel loses traction, applying some break pressure to that wheel will cause the other wheel to take hold.

dfkrug
Is the part you reshaped listed as an item # in post 3 of kennyd and if so, what is the item? Am thinking #12 is one or the other.

 

[beenthere]

What is a good way to test if the diff-lock is working?

I've never felt good about using it on my 4300, as have been too nervous about breaking something in the process. Also, never really knew that both wheels were locked in, as tough to see the wheels spinning (or not) when hidden be the fenders.

Usually (for me) if one wheel loses traction, applying some break pressure to that wheel will cause the other wheel to take hold.

dfkrug
Is the part you re-shaped listed as an item # in post 3 of kennyd and if so, what is the item?

Here is image of service book on removal. (sorry for TBN's double post)

 

[texasranger556]

It was icy out when I bought my tractor so I put one tire on an ice patch and the other on pavement. Held down the diff lock then hit the hydro pedal. The tire on the ice spun while the other on the pavement sat still.

If you have a loader you could push up against a tree and see if it spins both tires with the diff lock on vs off. Or jack up the back end and have someone hold the diff lock while spinning one wheel to see if the other turns the same direction (transmission in neutral). Even a worn diff lock may seem fine on a jack though.

You can certainly use the steering brakes to limit wheel slip, but it is nice to be able to just hold down the diff lock in certain situations.

 

[dfkrug]

Is the part you reshaped listed as an item # in post 3 of kennyd and if so, what is the item? Am
thinking #12 is one or the other.

Item #12 in the diagram is what I am holding in my hand in my photo. This side of the dog clutch
meshes with the 4 teeth on the ring gear, not in the diagram.

Using the brake on the slipping rear wheel will do the job of a diff-lock or LSD; that's what some
cars do with their ABS systems to control rear wheel spin. When the controller senses
wheel spin, it applies braking action to the offending wheel.