The drive for the screw is direct from the motor; just a shear pin connecting the two.
Disconnect the GDO from the door and see if the door opens/closes fully without undue effort. Then see if the GDO operates ok without a load.
If the door needs to be balanced, you can probably handle that if it is not a torsion spring balance. While you are at it, lube the pivot points or rollers with something like engine oil. Do not lube the track on a sectional door; that will collect dust and gum up the works.
If the GDO is not working right, you can get s replacement traveler at a home center and solve that. Lubing the screw and rail with lithium grease will help.