MTD self propelled walk behind help

[aka rotten]

MTD12BV829Q755 Replaced control cable,drive belt,mower wont move with handle engaged.If i raiser rear up while running wheels will turn untill weight is back on it.I would guess belt problem buy i installed it as it came off,any ideas?Thanks

 

[ILENGINE]

If the belt is working properly then the next two options are either the drive tires are worn inside and not engaging the drive gears, or the transmission is bad and will need to be replaced.