my old snapper lawn mower slows in 5th and 4th gear.what to do?

I have a 4 year old snapper that is doing about the same thing, but it has migrated all the way to 1st gear. I removed the drive wheel that has the rubber ring on it and am going to replace it as soon as I can find one. a friend of mine told me that you can lower the flat surface wheel that this rubber wheel rides on about 1/4" and it will increase the pressure the drive wheel is pressing against. this is the flat wheel that runs directly off of the engine shatf. He told me it might be easier to remove the engine to move the disk down rather than try to fight the location the set screws are located in on the mower. It appears to me that the rubber ring that rides on that flat wheel is slipping and increasing the pressure may help... good luck

Joe in Texas
July 2007