Pearson 323 -- Universal M4-30 -- I believe it's a Hurth Transmission. One day I noted what seemed like slippage -- found water in the fluid. Mechanic cleaned the venilating tube and changed the fluid three times. No more water -- good clean fluid. Once or twice I had the slipping problem again -- as soon as I lowered the RPM it went away. In totla, it only happened on three occasions in about three months. Any thoughts?