NX55 HST Jerky Transmission at Low Speed

[MinnesotaEric]

I bought the tractor new in May 2019 and the s/n is VW7xxxxxx.

The recall for 2019 apparently has nothing to do with earlier serial numbers. I will say this: my tractor has surged from day one when cold but only this past summer did it get bad and in hindsight, after eight years of ownership, I wish I never bought this machine.

 

[TN8Man]

The recall for 2019 apparently has nothing to do with earlier serial numbers. I will say this: my tractor has surged from day one when cold but only this past summer did it get bad and in hindsight, after eight years of ownership, I wish I never bought this machine.

Sorry to hear that. Do you plan on selling it or getting it fixed? If it was me I might see how much I could get at a dealer as a trade-in on a new purchase. Sometimes they give more than you could sell it on your own just to the sell a new tractor.

 

[MinnesotaEric]

Sorry to hear that. Do you plan on selling it or getting it fixed? If it was me I might see how much I could get at a dealer as a trade-in on a new purchase. Sometimes they give more than you could sell it on your own just to the sell a new tractor.

The machine is due for a full service and I'm planning on doing the service this spring and making a video about it. Rolling back to my initial thoughts, it could be a filter screwing up but more likely it is either the HST pump shims (unlikely) or the internal solenoid that controls the HST pump's volume (more likely).

I've got another new dealer who hired a proper tech and he and I discussed the issue after the tech determined my machine is not in the serial number range for the recall. The new dealer is part of a dealership chain (everybody has been consolidating) and the northern shop doesn't have the equipment to split tractors. As a result, the tech I spoke to has not directly worked on the HST transmissions, but the southern shop has, and so he shared what the southern shop had learned.

Anyway, since I'm not made out of money, I have no recourse other than to let it buck, or split the tractor myself in the summer using my payloader to lift the cab up and off and I'm inclined to let it buck.

 

[TN8Man]

The machine is due for a full service and I'm planning on doing the service this spring and making a video about it. Rolling back to my initial thoughts, it could be a filter screwing up but more likely it is either the HST pump shims (unlikely) or the internal solenoid that controls the HST pump's volume (more likely).

I've got another new dealer who hired a proper tech and he and I discussed the issue after the tech determined my machine is not in the serial number range for the recall. The new dealer is part of a dealership chain (everybody has been consolidating) and the northern shop doesn't have the equipment to split tractors. As a result, the tech I spoke to has not directly worked on the HST transmissions, but the southern shop has, and so he shared what the southern shop had learned.

Anyway, since I'm not made out of money, I have no recourse other than to let it buck, or split the tractor myself in the summer using my payloader to lift the cab up and off and I'm inclined to let it buck.

View attachment 779769

My local Kioti dealer said my serial number was not part of the mandatory upgrade. Now that winter is almost over I'll be on the tractor soon and reevaluate the issue I experienced just before the tractor went into winter hibernation. This was the intermittent jerky motion when using the stump grinder while creeping forward over the stump. The main problem I had that required the HST replacement is fixed now under warranty. That was the bucking and loss of reverse motion while using the grooming mower on hot days and hilly terrain, I could feel the heat radiating from under the tractor while stepping out of the cab.

 

[TN8Man]

Been back on the tractor for a few months and reevaluating the issue of hydraulics system jerking after using PTO for a few hours.

When I use the tractor without the PTO I have no issues no matter how long I use it.

When I use the PTO the problem only occurs after a few hours and when I get out of the tractor I can feel the heat from the HST/transmission underneath.

I'm pretty sure now this is a hydraulic fluid overheat issue. I'm going to attach a thermocouple to the HST/transmission to verify this but it's pretty obvious.

I'm at my 400 hour maintenance period now so I will be changing hydraulic fluid and filters. I need to review specs to pick the best fluid to handle the heat.

Looking at the hydraulic cooler setup it appears the hydraulic fluid cooling design is far less than optimal. The tractor cooling design stack up starts with the engine fan, engine radiator, hydraulic cooler, a/c condenser and finally the fuel cooler and the plastic fan that is supposed to pull enough airflow through all that with heat added from each preceding radiator. The hydraulic cooler has very little space to visually see obstructions let alone attempts to remove it and as I looked at it today it does have crap on it.

I'm thinking my problem might possibly be not enough hydraulic fluid cooling (heat dissipation) to equal or surpass the heat load generated when using the PTO and just cleaning the radiator might not be enough.

 

[Robin Veerman]

I’ve been using AMSOIL’s Tractor Hydraulic/Transmission fluid in my CK30HST since new. I’m impressed with how well the tractor operates in the Canadian cold winter temperatures, like it’s the middle of summer, and seems to work great during the mowing season too! I’ve done a UOA at 300 hours and it was determined that it was good for continued service. I changed both filters, topped off the fluid, and will sample at the next 300 hours. I wanted the best lube and since there’s no Universal specifications for hydraulic oil, like engine oils or gear lubes, I decided to use Amsoil after reading the specs on it.
I copied some info below…
“AMSOIL Synthetic Tractor Hydraulic/Transmission Oil is recommended for equipment combinations of transmissions, hydraulic systems, final drives, power take-off systems and wet brakes operating in "all-weather" hot and cold temperatures, including, but not limited to, those listed below. Consult your owner's manual for specific application requirements:

• Farm tractors and equipment
• Fork lift trucks
• Off-road equipment
• Lawn tractor hydrostatic transmissions
• Golf course mower hydrostatic systems
• Some 4x4 ATV models with wet-brake differentials”

Here’s a link for you to check out the info on it. I’m sure others will share their experience…

https://www.amsoil.com/p/synthetic-tractor-hydraulic-transmission-oil-sae-5w-30-ath/?zo=331384

 

[DieselBound]

I've had zero issues with mine [2016] (now at 850 hrs), even in 90 degree temps running a 7' flail and with AC on. This was even with sub-optimal hydraulic fluid ([Shell Rotella] a little on the thin side). This past winter I switched to Triax Agra UTTO XL (synthetic blend) and have so far found that it works great: winter performance was a LOT better.

 

[dusty3030]

I just got the new software update done on mine. Cured the jerking. Check with your dealer again and have them see if yours could be updated anyway. Mine was done for free They came out to the farm installed an extra ground strap in the cab and did the update - jerking is gone.

 

[TN8Man]

I just got the new software update done on mine. Cured the jerking. Check with your dealer again and have them see if yours could be updated anyway. Mine was done for free They came out to the farm installed an extra ground strap in the cab and did the update - jerking is gone.

What year is your tractor?

 

[dusty3030]

2020.