TC34DA HST petal sticking

[Fork14]

Worked fine until last night. The pedal got progressively harder to push and stays where you place it, not coming back to neutral. I greased the pivot of hst pedal and checked fliud levels. I even pulled the fuse for the cruise control as it feels as if the cruise is partially engaged. Pedal sticks whether in forward or reverse. Anyone have a solution?

 

[TMB1320]

This has started to occur on the 1320 here. This is an old post, so bump it as no
one replied. Is there something in the cruise control that needs lube/attention?
It just started sticking just lately. Any insight around? I'll have another search in the mean time..

 

[RobertN]

How often were the cross shaft zerks greased? It might just be gummed up; new grease wont help if it is gummed up. May need partial disassemble, regrease, then stay on the lube schedule. My TC40DA book says to lube that every 50 hours.

 

[TMB1320]

Cross shaft? Do you mean the pedal pivot shaft? The fit there is worn somewhat and so there's a little
play, so not source of bind IMHO. Where does the pressure normally come from to return HST to neutral when foot off the control? Or something in the cruise mech dragging?

 

[jinman]

Robert, the TC34 is mechanized quite differently than our Class III Boomers. I don't believe there are any grease zerks on the mechanism. I think TMB1320 needs to look at the diagram below and consider pulling off the cowling under the steering wheel on the right side. Once under there, he should be able to to see all the movements of the HST treadle and attached parts. He can use some spray lube to help loosen any binding parts. However, he needs to realize that engine RPM has a large effect on the pedal returning as it should. If he makes large pedal movements with the engine RPM low, the pedal will tend to stay depressed. With large pedal movements, it's best to keep the engine well above 2000 rpm for the best HST response. If the transmission stalls due to low RPM, the pedals will also stall in place and not return to neutral as they should.

 

[TMB1320]

TY Jinman. I'm leaning toward low rpm, however something has changed. I've had this machine for about a year now and still learning the quirks. Transmission stalls. Not sure what that means. Anything to do with the sound it makes when activating treadle with park brake on?

 

[jinman]

TMB1320, an HST stall is when the pressure from the pump gets so high that internal relief valves open to keep the HST pump and motor from blowing seals. It's when you put the pedal down and the tractor stops, but the engine is still running. The pressure inside the pump/motor is around 5000 psi when that happens. If the engine is running fast enough, it will keep the charge pump going (the charge pump supplies low pressure to the main HST pump [150-250 psi]). The charge pump also can supply pressure to operate the swashplate to send it back to neutral. However, if the rpm is low and the HST goes into relief bypass, the engine can really lug down and the rpm is so low that the charge pump puts out very little pressure/flow and everything just sits where it is. Just understand that the HST works on pumps and pumps can't supply much if they are turning at a slow rpm. It makes perfect sense when you think about it. Yes, that's the big whine/groan you hear when you press on the treadle with the parking brake set. It's like Olympic weight lifters grunting loudly when they are lifting heavy weights.

This return-to-neutral can be aided with a return spring on the pedal/treadle, but if you get that return spring too tight, you get fatigue with your foot holding the treadle down all the time. It's a balance between return pressure and ease of operation. With the engine rpm up, everything works much better. Still, the shafts go through bushings at the pivot points and these can become dirty and tight, making pedal movements restricted. It's good to check at least annually and make sure everything is free and lightly lubed. Too much lube just attracts dirt, so a small amount is best.

 

[RobertN]

Interesting; I dont see one in the diagram. The TC40D does, the Kubota B8200HST that I used to have does, as did the '41 Farmall A I had.

Robert, the TC34 is mechanized quite differently than our Class III Boomers. I don't believe there are any grease zerks on the mechanism.

 

[showcattle]

There is one under the right side of tractor under the hydraulic hard lines. Takes a trouble light and some searching. At least that's where it is on our NH 2210 which is basically the same tractor.

 

[Halftrack]

Although an old thread, I'm not sure whether Fork14 ever solved his problem or the other contributors either. I'll add my experience to the mix and maybe a solution will boil out of the pot. Basically the same problem as Fork14, pedal would stick and not return and especially bad after using the cruise control. After removing side panels, found the cruise magnet plate (item 2 in above diagram) was rubbing on the plastic fuel tank during a portion of its swing. I dismantled the mechanism and ended up grinding the edge of the plate down to gain more clearance. There may have been a possibility of moving the fuel tank forward, but I wanted to dismantle the linkages anyway to lube the pivot points. This solved the clearance issue but I still noticed the cruise control hanging up upon disengagement of the solenoid. My solution to this was to glue some thin nylon strips on the solenoid face between it and the plate to facilitate a clean release upon disengagement. I used 4 strips of a wire tye spaced around the perimeter of the solenoid, but 3 probably would have been adequate. At the time, I wondered if full contact was necessary between the solenoid and plate to keep the solenoid from overheating, but it has worked perfectly since (3 years ago). And of course the pedal pivot shaft needs to be periodically lubed and its a bear to get to. My 2 cents.