RTV X900 HST Repair

[jhuggans]

Bought a broken 2018 X900. Was told the transmission was bad as it would only barely move forward or backward. After reading other stories I assumed it had to be the HST. My first move was to add hydraulic fluid to the reservoir, which was about two gallons low. No change. Pulled off the HST today and found this. Seems pretty straightforward with what is causing the lack of movement but my question is two parts; I see zero appreciable damage anywhere other than the two plungers so would that mean everything is fine after replacement and secondly, how could this happen to just two?

I bought the machine for $3k so putting some money into this is worth it to me. Just want to make sure I prevent this from happening again.

 

[OlFerguson]

Any wear on the swash plate

 

[jhuggans]

Any wear on the swash plate

Need to get a better picture. The line seen on that bearing surface is perfectly smooth.. No lip.. Can't even feel it with a fingernail. The bearing surface on the other side is immaculate, zero wear. I can get a better picture tomorrow.

 

[Nicksacco]

Nice job of diagnosing and repair.

What do you think happened?

It appears that the piston shown was "hammered".

I wonder if lack of hydraulic oil and/or water in the system would cause the system to "hammer" as it starved for oil under a significant load?

Is that a "groove" worn in the swashplate from the damaged pistons?

What does the other piston look like? same?
Any big chunks of metal to be seen?

I'd be curious what the 3 filters in the system caught.

Check the unloader and associated linkage too. If the linkage gets out of adjustment it makes shifting difficult - a possible contributing factor.

 

[TECH101]

Bought a broken 2018 X900. Was told the transmission was bad as it would only barely move forward or backward. After reading other stories I assumed it had to be the HST. My first move was to add hydraulic fluid to the reservoir, which was about two gallons low. No change. Pulled off the HST today and found this. Seems pretty straightforward with what is causing the lack of movement but my question is two parts; I see zero appreciable damage anywhere other than the two plungers so would that mean everything is fine after replacement and secondly, how could this happen to just two?

I bought the machine for $3k so putting some money into this is worth it to me. Just want to make sure I prevent this from happening again.
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Most models have a tank located underneath the passenger seat, it that is empty or low the machine will not drive forward or reverse