I have a Tuff Torq hydrostatic transmission (model: 7A646084591) that I'm suspicious of, but I can't quite figure out the best way to troubleshoot. I'm looking for a way to determine if:

  1. The transmission has something wrong with it internally and needs service/replacement or
  2. The transmission is working correctly but just under increased load and seeking "even pressure condition" (as described in this cub cadet post).

I'm totally green with this kind of thing, so any telltale signs to look for or other troubleshooting steps would be appreciated. I'm hoping I can determine that I don't need to replace the transmission...

What I've tried:

  • The transmission was making a whining noise, so I pulled the vent cap and topped of the oil. I contacted Tuff Torq they reccommended using TuffTech Oil (Part # 187Q0899000), but said it's a 10W-30 base oil, so I just used that. After refilling it lost some fluid (assuming through the vent cap, because I put too much in) but it hasn't leaked since the first top-off.
  • 1
    Did you change the filter when you changed the oil? If not, it could be causing a lack of fluid transfer between the two chambers, which might be causing noise. Just a thought. May 15, 2023 at 17:27
  • @Pᴀᴜʟsᴛᴇʀ2 I did not, and I didn't know it had one. I just topped it off hoping to avoid completely disassembling the transmission before knowing if that was actually necessary. Do you think I should go for the filter next?
    – cam.b
    May 15, 2023 at 21:12
  • 1
    I don't know if it would or wouldn't help. I was just thinking possibly a complete oil change with a new filter might make it a bit better, but on the other hand it could be a complete waste of money. You might try pulling the old filter out to see what shape it's in. Often, if there are internal problems, you'll see "stuff" you wouldn't expect to see in the pleats of the filter. May 15, 2023 at 21:35
  • Got it, thanks @Pᴀᴜʟsᴛᴇʀ2! I'll give it a shot when I exhaust easier options and report back.
    – cam.b
    May 15, 2023 at 23:01
  • Update here, the leak has continued and I've done some troubleshooting but nothing easy. I talked with a local tuff torq tech and they said that there is a $400 repair kit, but with labor it isn't worth it vs price of new one, plus shorter warranty and no guarantee it will fix it. They recommended I just purchase a new one and replace it myself. A cool $800 later... I'll tear into old one once new one comes and see if I can fix it. But for now I just need it to work. Thanks again for the help!
    – cam.b
    May 23, 2023 at 16:34


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