L6060 + 3rd function + BH92: grapple deadheading “feeds back” into backhoe - dealer says I must disconnect BH hydraulics. True?

[WMK]

TL;DR: New L6060 (51 hours). BH92 hydraulic thumb was repaired early on. Lately I’m seeing weird hydraulic behavior: when I max open/close the grapple (3rd function), it feels like pressure/flow is feeding back into the backhoe circuit. Dealer says Kubota told them I can’t have the backhoe hydraulics connected when using the grapple (I can leave the hoe mounted, just unplug the BH hoses). That sounds odd to me. Looking for real-world experience from L60 owners and any plumbing/WSM wisdom.

Machine / setup

• Tractor: L6060 HSTC (brand new; now ~51 hours)
• Loader: LA1055
• Backhoe: BH92 with hydraulic thumb
• 3rd function: (factory kit on loader joystick) feeding a root grapple

Timeline

• Delivery: hydraulic thumb on the BH92 wasn’t working right. Dealer took it back, replaced a lot of seals, and returned it “fixed.”
• After repair: both backhoe and thumb felt fine.
• Then: the left lever on the backhoe (boom/swing) started feeling stiff/tough.
• Soon after: while using the grapple, if I hold the button and deadhead at max open/close, I notice what seems like pressure/flow feeding the backhoe circuit (symptoms below).
• I kept working until the 50-hour service. Dealer picked it up for the scheduled service and to investigate the backhoe/3rd-function oddity.
• Now: Dealer says Kubota told them I cannot have the backhoe hydraulics attached when using the grapple. They advised I can keep the hoe mounted, but I should disconnect the BH couplers. Everything seems to work again, but I only have ~1 hour on it since.

Symptoms

• When I deadhead the grapple (max open or max close on 3rd function), I feel like pressure is getting pushed into the backhoe valve.
• Prior to service, the backhoe left joystick got noticeably stiffer.
• No obvious leaks; just that “backfeeding / loading” sensation on the hoe side when the grapple hits end of stroke. Can also hear the flow going back (when it had the issue)

The dealer told me “Kubota says you cannot have the backhoe hydraulics attached when running the grapple. Leave the hoe on if you want, but disconnect its hydraulic couplers.” I’m trying to understand why that would be required on this platform. Many folks seem to run grapples with the hoe on and plumbed.


What I’m asking the OTT brain trust

• L60 owners with BH92 + 3rd function: Do you run your grapple with the backhoe hydraulics connected? Any issues?
• Hydraulic plumbing logic: Is there a sound reason the BH valve being in-circuit could see damaging back-pressure when I deadhead the loader’s 3rd-function (given typical L60 plumbing)?
• Misconfiguration? Could the dealer have misrouted PB/return during the thumb repair or 50-hour service (e.g., swapped quick couplers, PB to tank, etc.) such that relief flow from the 3rd function is loading the BH valve/case?
• Relief / priority checks: On the LA1055 + factory 3rd function, where is relief supposed to crack first during a 3rd-function deadhead? If that’s correct, should the hoe “feel” anything in neutral?
• BH92 specifics: Anyone have the BH92 WSM section that covers correct inlet/outlet (PB/return) orientation, color-coded hoses, case drain (if any), and allowable back-pressure on the BH valve?
  • If sharing the WSM isn’t allowed, tips or page references are still hugely appreciated.

I’m totally open to correction here and I really appreciate any time spent helping me understand this. If the dealer’s statement is right and there’s a good hydraulic reason to unplug the hoe when grappling, I want to learn why. If it smells like a plumbing/config issue, I want to fix it the right way.

I appreciate any and all guidance, thankyou for taking the time to read and comment.

P.S. If someone can share the BH92 WSM (or at least the hydraulic section / hose routing diagrams) that would be amazing. If sharing is a no-go, any guidance on the critical pages to request from my dealer would help.

 

[Old Machinist]

Why are you deadheading the grapple at max open/close to begin with?

 

[WMK]

Why are you deadheading the grapple at max open/close to begin with?

I’m not holding it on relief for long - just the quick bump you’d use to snug a log or fully open before grabbing a pile. My concern isn’t the brief deadhead itself; it’s that when I do that, the backhoe circuit/lever feels loaded. From what I understand, with the hoe in neutral that shouldn’t happen, which makes me think return-to-tank/PB plumbing might be wrong somewhere. Do you see a reason the BH valve should feel it during a momentary 3rd-function deadhead? (I very much could be using the word wrong, I know it to mean; holding the valve ON when the cylinder is already at end-of-stroke (no flow path), so the system jumps to relief pressure)

Thanks!

 

[Old Machinist]

Sounds like something went askew since it worked fine after the first service. Make sure none of the backhoe levers are sticking beyond center. The SCV for the backhoe should flow to return just as well with all the levers in neutral as the power beyond does with the bypass hose in place.