NX55 HST Jerky Transmission at Low Speed

[TN8Man]

Fly by wire, no linkage on OP's tractor.

My NX can be jerky as hell usually on medium range pedal to the floor and it's when the fluid has warmed up. I can set cruise and it stops and travels smoothly. I've figured out a bunch on my tractor but not this one yet.

My jerky motion also only seems to occur when the hydro fluid is hot. Normally the hydro fluid only gets that hot when I'm using the PTO for an extended period of time.

In my manual section 4.7 HST CONTROL SYSTEM (HST MODEL) it shows a oil temp sensor. I want to find out how to get the transmission oil temp sensor data to a dash mount readout.

Anyone have any ideas?

 

[MinnesotaEric]

Locate the sensor. If a single wire, it works by grounding and you can tab a temp gauge into it.

 

[TN8Man]

I'm going to look for it but the diagram shows a iron core inductor symbol instead of the usual resistor type temp sensor. I did a internet search for a Kioti oil temp sensor part but can't find anything.

 

[MinnesotaEric]

I'm going to look for it but the diagram shows a iron core inductor symbol instead of the usual resistor type temp sensor. I did a internet search for a Kioti oil temp sensor part but can't find anything.

If it is a two-wire, then one wire is the signal, and the other wire is the reference voltage. You want to tap into the signal which will be a lower voltage than the reference voltage. Reference voltage comes out of the ECU, and is modified by the sensor. The reference voltage may be battery volage, maybe 12v or something less.

 

[justman777]

I've experienced both trans surging, and the jerkiness the OP mentioned. For surging, it's always with the forward pedal depressed almost to the floor. Seems like there's a "sweet" spot that causes it to switch between surging and not surging. For jerkiness, it's always when I depress the reverse pedal just a bit, usually backing up to an implement. I theorized the potentiometers in the pedals were sending "odd" or intermittent voltages to the TCU, causing the surging or jerkiness. It made sense to me, because the surging happens very near the high end range of the forward pedal, and the jerkiness happens at very near the low end range of the reverse pedal. It'd be interesting to probe the wires to see what the voltages look like across the range of the pedal movement, because they should be pretty linear across the entire range. If the voltages increase linerally, and then at some point increases (or decrease, depending on how the potentiometer works) abrubtly, that would cause the TCU to surge. If the voltage is intermittent (on/off), that could cause the TCU to turn on and off and subsequently cause the trans to jerk. Of course, it could also be the programming in the TCU that commands a sudden power increase (surging) For instance, a reference voltage of 2 volts (notional) is your "stopped" setting for the TCU. As you depress the pedal, the voltage gradully increases from the pedal potentiometer, causing a commensurate power setting in the TCU. At some point, however, the TCU programming interprets a particular voltage from the potentiometer at around 90% of pedal travel to actually be the 100% power setting, causing the trans to surge. All this is theory though. I'm away from my tractor right now, and don't really have a means to test.

 

[Eat Your Veggies]

Anyone have an issue like this?

While using my PTO stump grinder in low gear where I need to be able to move slowly the transmission is jerky.

It might not be the same issue, but have you had the dealer do the NX update that came available in May (I think) of this year? The dealership in my area had a “stop sale” order for the recent in-stock NX series from 2020 forward pending release of the update. It was due to operational issues much like you describe.

Specific details are sketchy, but from chatting with my dealer, it involved several new grounding straps and a software tweak. Supposedly, this fix applied to the NX series a fair bit older than my 2020.

 

[justman777]

It might not be the same issue, but have you had the dealer do the NX update that came available in May (I think) of this year? The dealership in my area had a “stop sale” order for the recent in-stock NX series from 2020 forward pending release of the update. It was due to operational issues much like you describe.

Specific details are sketchy, but from chatting with my dealer, it involved several new grounding straps and a software tweak. Supposedly, this fix applied to the NX series a fair bit older than my 2020.

Did your dealer happen to mention an update number or reference source? It'd be sweet if a software update and a few grounding straps fixed the issue(s).

 

[TN8Man]

Thanks for the info!
I have not had my tractor in the shop this year, I do my own regular maintenance. I'll have to call the shop about this. I bought my tractor new in mid 2019.

 

[Eat Your Veggies]

Did your dealer happen to mention an update number or reference source? It'd be sweet if a software update and a few grounding straps fixed the issue(s).

Not that I recall, but I’ll contact them for a reference and post it here. I’ve only put 30 hours on the tractor - mostly moving snow- but have had none of the heretofore mentioned transmission issues so far.

 

[Eat Your Veggies]

I emailed my dealer for the info regarding the issue. Heres their reply:

“The Stop Sale Bulletin is DOCUMENT NUMBER: US/CA-020922 and the Mandatory Service Bulletin is DOCUMENT NUMBER: MSB050322UC. If the dealer recently got the tractor, Kioti would have taken care of it already. If it was a tractor received at the dealership before February 2022, then it might potentially still be affected, but I'm sure most, if not all, of the affected units have been repaired and sold.”

There were delays getting the parts necessary for the fix, so I had to wait longer than anticipated. The speculation for the delay was that Kioti prioritized issuing the kit to dealers for ‘recall’ tractors already sold and in use before sending it to Stop Sale units. In retrospect, the delay could have been supply chain or other reasons.

It doesn’t seem like there are many significant changes from year to year in most Kioti models. If I had an NX that was less than 5-6 years old AND had jerky transmission or other quirks, I’d contact my dealer.