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larryuno

Hydro Gear rebuild apparently failed

larryuno
2 years ago

Hi, I have a Poulan 300 EX, with a Hydro Gear T2 type transaxle. I recently spent much time to learn how to rebuild a hydrostatic transaxle. Although installing the center section, pump shaft, the swash plate and the two piston blocks as one unit was a huge challenge, I thought I had finally gotten it right, and turned the pump shaft to check that it turned freely. But after install I have spent at least an hour trying to purge the unit, bypass on, bypass off, and when it's bypass off sliding into forward or reverse causes a distress sound. I tried to record it but don't see how to attach the file here.


I replaced center section, the two piston blocks, both bearings with two races each, the seals. I had placed the bypass tab, yes, and when moving the direction lever in bypass, the machine makes no noise, just when the bypass is off. Upon assembly and torquedown of the center section, I moved the pump shaft to see that the pump block moved freely. I also placed the input pulley and turned the input shaft, to see that everything moved freely. I used 20-50w synthetic oil, but lacking enough oil with 2 quarts I topped it off with a 1/4 cup of a heavier Bardahl type additive. After initial purge actions, I checked the level, and saw froth on top of the oil, and the level dropped slightly, so I bought another quart of the synthetic oil and topped it up, a slight amount. I had always assumed the heavier additive would just dilute in the oil and make the oil only very slightly heavier, but am wondering if the difference is somehow preventing oil from passing the filter? The new center section came with a filter but I didn't pay it much mind; do they come with a protective surface that needs removing? Finally, the wheels do not move: in both forward and reverse lever there is maybe a slight nudge but no movement. Spinning the wheels by hand, they move freely in opposite direction, as always. Someone suggested I try to move both wheels the same direction in bypass, and found that doesn't happen. Do I assume I move immediately to another teardown, or is there more to check first?

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