Craftsman Hydrogear HST

[Sysop]

I have a Craftsman lawn tractor with a Hydrogear HST that I think may be on its last leg. It's not like any of the failures of HSTs I've experienced, so I thought I'd post here for some ideas. Most HST failures I've seen either make horrid noises and do nothing, or get so they'll not pull slopes once warm. Mine has only acted up when cold. First time it did it, I started it up after it had set a few hours and started to back down a slope. It jerked around like it was partly freewheeling and partly being held back by the tranny. I stopped, pulled the little clip that disengages the HST from the drive wheels and cycled the HST through it's ranges, reset the little clip to re-engage the drive wheels and it operated fine for a couple hours until the task was complete. Few days later, cold start, again wouldn't pull. On flat ground it would surge and drift repeatedly (maybe moved a total of three feet). Disengaged the drive wheels and cycled the HST again, everything was fine for the couple hours of operation I put on it. Once done I put it on a trailer to take elsewhere for another bit of cutting I needed to do. Next day hooked up the trailer and went to do the other cutting, this time I started the tractor, disengaged the drive wheels and let it set there with the HST engaged while I unstrapped it from the trailer and never had any issues. Seems disengaging the drive wheels and engaging the HST to let it warm up (maybe a total of 2 minutes to do so) is preventing me from having any issues, but I'd rather see if there is a repairable cause before the unit fails as it is a $500 unit. I was considering removing it and changing out the fluid to see if that helps.

Any thoughts?

 

[SageBrush]

See if you can rebuild it. Get the model number and call the manufacture.

 

[mostly_gas]

I would change the fluid if practical. Can't hurt