HST Power Loss on Kubota Grand L3940 HST+

[slowzuki]

You mention backhoe, is the diverter valve that you throw to run the backhoe in the right positions / hydraulic connector plugged back into the loop? The loader is before this and will operate normally while the remotes are deadheaded.

 

[hawkeye08]

I don't know what the HST+ means, but is that some sort of auto throttle? If you have it running with the hand throttle at 2500 rpms, does it still bog down?

 

[RobK]

Hi Hawkeye and others;
My Grand L3940 just has the FEL, no backhoe or other remote hydraulics. I'm setting the hand throttle at 2,500 rpm's before pressing the HST pedal...which bogs engine... I could brush hog, but barely and in Low Ranges on level ground.

HST+ is the newest HST on the Grand L's. It gives an option for auto-throttle response to the HST pedal and also an additional Hi/Low HST range within each L/M/H of the Hydro-trans. I've tried turning auto-throttle on and off with no change in behavior. BTW, I LOVE(d) this new trans and entire tractor up to this current(and hopefully fixable) issue.
Thanks,
Rob

 

[Happyman]

Sounds like something has bound up in the drive train. I also have an L3940 and the symptoms you mention are exactly what happens to me when I try to drive forward or reverse when the brakes are locked on. I would check to see if the brakes are stuck. Is it 4wd? If so, check to be sure nothing in the front drive train is bound up or if the 4wd is still engaged and not properly disengaging. I think it's not an engine or fuel problem, but either the HST pump or mechanical drive train problem. See if you can put the tractor on a hill and drop it in "N" and see if it free wheels down the hill. That would eliminate some possibilities and then, most likely, be a problem with the HST drive pump.
Keep us informed.:thumbsup:

 

[dex3361]

+1 for checking for the brakes dragging.

 

[RobK]

Hi to All;
I was just out in Ohio over the weekend, but couldn't get to the dealer when they were open. I did get to run my L3940 to load a 3pt. rear blade to bring home to PA though... When HST is engaged forward, the FEL won't operate normally or sometimes at ALL... when still, it's a bit sluggish and the lever is stiff. It seems to stick, which it has never done. All issues seem to point to a HST / Hydraulic issue as the engine runs great and has been serviced as it should have been.(I was mistaken about the filter, as it was replaced, not cleaned)

Anyone else with suggestions concerning the HST or hydraulic issues?
Thanks so much... I'll post when we have solved the issue.
Rob

 

[Happyman]

Still sounds like a pump problem. The HST uses fluid to drive the wheels and the same fluid to raise and lower hydraulics, all with a pump system. I would get the dealer involved and not use it until the dealer can look at it. You may run the risk of busting a seal somewhere and making a mess or damaging some other part of the hydro system.
Keep us informed. :thumbsup:

 

[dex3361]

I would look at the suction filter being restricted if both the HST and FEL are having issues. Do not keep trying to use the HST if you are starving the system for hydraulic fluid. The HST depends on hydraulic pressure to maintain clearance between the swashplates and pistons. It could be a very simple fix that if not dealt with could cause expensive damage to the system.
It may be drawing air into the suction side of the hydraulics.

 

[mkane09]

Just for grins and chuckles, try disconnecting all the quick connects for the FEL and re-connect them. I had a similar problem with my MX4700HST after changing a bad hose on my grapple. Brady Barlow told me that it is often a QC that isn't fully seated. It fixed my problem. Good luck....

 

[slowzuki]

The HST and other hydraulics are independent systems, just common reservoir of fluid they draw from.