I thought I'd mention that it seems to be getting harder to find the DEXRON II/III ATF needed for our Hurth transmissions. The auto stores that I frequent are no longer carrying it, and it seems like some manufacturers are no longer making it. Just as with motor oil, stores are increasingly only carrying synthetic lubricants.
I've become very picky about ATF, and will never put synthetic ATF in my transmission. As described in this prior post, my boat's transmission had been rebuilt a year before I bought it, and based on the way it was slipping and taking several seconds to engage in forward a mechanic suggested that the previous owner may have filled it with synthetic fluid:
https://c34.org/bbs/index.php/topic,11703.msg94682.html#msg94682
I refilled with STP DEXRON II/III oil and it got mostly better, and with a couple subsequent annual changes it got completely better. Based on this experience I have become a little paranoid, wanting to use the exact same ATF forever. I went back last fall to get some more, and STP had changed their product labeling to something else (similar but not identical), and the resulting confusion led me to delay the purchase and use up what I had of my good stuff. This weekend I went looking for the new STP ATF that I saw last fall, and that has now been discontinued with no DEXRON II or III replacement. I found a Castrol DEX/MERC on clearance and bought a couple quart bottles which should last me 5 years. Walmart has Valvoline DEX/MERC, but only in gallons, and I didn't need a 10 year supply.
Do not use DEXRON VI or later, those are significantly different from what Hurth specifies. And don't wait until the day before you need to change your ATF - it might take a little while to find the right DEXRON II/III product.
I've become very picky about ATF, and will never put synthetic ATF in my transmission. As described in this prior post, my boat's transmission had been rebuilt a year before I bought it, and based on the way it was slipping and taking several seconds to engage in forward a mechanic suggested that the previous owner may have filled it with synthetic fluid:
https://c34.org/bbs/index.php/topic,11703.msg94682.html#msg94682
I refilled with STP DEXRON II/III oil and it got mostly better, and with a couple subsequent annual changes it got completely better. Based on this experience I have become a little paranoid, wanting to use the exact same ATF forever. I went back last fall to get some more, and STP had changed their product labeling to something else (similar but not identical), and the resulting confusion led me to delay the purchase and use up what I had of my good stuff. This weekend I went looking for the new STP ATF that I saw last fall, and that has now been discontinued with no DEXRON II or III replacement. I found a Castrol DEX/MERC on clearance and bought a couple quart bottles which should last me 5 years. Walmart has Valvoline DEX/MERC, but only in gallons, and I didn't need a 10 year supply.
Do not use DEXRON VI or later, those are significantly different from what Hurth specifies. And don't wait until the day before you need to change your ATF - it might take a little while to find the right DEXRON II/III product.