I have a 1996 MTD Ranch King, 18.5 hp, 46 inch mower deck. When I go up small inclines in 3rd gear or higher, the belt between the engine and the variable speed pulley slips. I thought a higher spring tension on the transmission belt would help, but it doesn't. I have disassembled the variable speed pulley and cleaned and lubricated the shaft. I have also replaced both drive belts with OEM belts from MTD.

Never lube a variator pulley this will cause it to stick and not move up and down.