I just fixed this issue on my Troybilt 33. It was the belt. Most 1770334 belts out there are soft rubber outer shells. If the belt is soft rubber it adheres to the motor pulley when not engaged. That causes the mower to creep. It also makes it difficult to shift gears because the transmission pulley is always being driven. The belt needs to have a fabric wrap on the outside. The following belt will fix this issue. I can't post links as I'm new to this forum.
www vbeltguys com 1770334-troy-bilt-oem-equivalent-dry-kevlar-v-belt
www vbeltguys com 1770334-troy-bilt-oem-equivalent-dry-kevlar-v-belt