This spring is is the main return spring that fits in the gearbox selector mechanism, and it is the wear of this spring over years of use that causes it to eventually causes it to lose it's tension - which then results in changing gear becoming more haphazard and less direct.
As always, this spring was copied from an original pattern in very good condition. Fitting it is a relatively simple exercise - remove the end cover to reveal the selector mechanism, then undo the two nuts holding the Return Spring Cover Plate, which allows the removal and replacement of the old spring. This spring fits both upright pre-war gearbox's, post-war upright gearbox's and laydown pre-AMC Norton gearbox's.
A simple fix if not already done that can greatly improve positive gearchanges