LS4046 HST hydrostatic drive anomoly

[dhvd79a]

I was doing some loader work and experienced a problem.

First a brief description of normal operation. Forward and reverse pedals are easy to press and when I remove my foot the tractor comes to a stop quickly. I seldom use my brakes.

The problem: After about 90 minutes of loader work the pedals became progressively harder to press while working. The harder they got to press the more the engine would bog down to the point where I thought it would stall. When I removed my foot from the pedal the tractor continued to coast. I had to use the brake to stop.

I had to stop for a couple hours and when I came back everything worked as normal.

My guess is that it is a heat problem. Has anybody else experienced this and if so any suggestions on how to fix it? Oh and my cousin said his Kubota does something similar.

Thanks
Dave

Should have mentioned fluid levels are correct and all fluids and filters were changed before this season. The tractor is primarily used for mowing but it mostly sat this year do to our long drought. Probably has less that 20 hours on it since the fluids were changed.

 

[seville009]

My MF1540 hst basically acts the same way. My hst pedal won’t return all the way to neutral position by itself; always use my toes to raise it back to neutral (or push on the back pedal a bit). Used to have a Kubota B7500 that was similar. May be just the nature of the beast - hydraulic fluid warming up or something; filter clogged a bit. Hasn’t really bothered me; used to it by now.

 

[dfkrug]

Neither of these HST experiences are good. If the HST rocker pedal (or dual go pedals) does not return to neutral on a warmed-up tractor, something is wrong. I do not know the MF or the LS, but I suspect both are direct-acting swash plate HSTs, not servo-controlled.

When failure-to-return to neutral happens with warmed up and above-idle-RPM HSTs, the first thing to look at is the mech underneath the floor. There is a grease zerk on the pivot, usually, and linkages that must be kept lubed and free of debris.

If the pedal(s) work normally until the oil gets really hot, the culprit is likely to be oil contamination (water in oil), or worn pump(s). There is a charge pump, plus a variable-piston pump in the HST.

 

[nybirdman]

Did use "Kubota"branded fluids?There has been some problems using other than factory fluids in Kubota's.