Traction 4200 Hydrostatic positive lock won't engage completely

simonds · Oct 31, 2015

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 · Oct 31, 2015

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

kennyd · Oct 31, 2015

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 · Nov 10, 2015

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

texasranger556 · Nov 11, 2015

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 · Nov 11, 2015

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 · Nov 11, 2015

dfkrug said:
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 · Nov 11, 2015

texasranger556 said:
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 · Nov 11, 2015

dfkrug said:
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 · Nov 12, 2015

texasranger556 said:
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.