I have a 265H and recently purchased a 266H Wheel Horse. The hydro drive assembly on my 265H has a 3 pulley assembly and my 266H has a 2 pulley assembly. The hydro drive belt on my 266H keeps disconnecting from the pulleys when using. I have adjusted the tension but the left side of the belt (non pulleyed side) is vibrating significantly and this is causing the belt to come off the pulley. I am wondering if a part is missing or if there is a belt guide mechanism which is missing. I have recently replaced the drive belt on my 265H and this was very straight forward with regard to fitting and tensioning the drive belt - this appears not to be the same case on the 266H. Any thoughts appreciated.