Why does starter keep breaking?

Starter Failures

There could be several causes for a starter to fail, but when replacement starters continually fail I have found one cause.

It is critical that a starter's gears be in perfect alignment with the gears on the flywheel. If the alignment is not perfect, then massive forces are imposed on the starter gear, and thus are transmitted to the shaft, and finally the bearings/bushings.

These forces rapidly accelerate the wear of the internal components of the starter and thus cause premature failure.

For years in the "old" days, the problem was so bad that most auto manufacturers used "shims" between the starter and the mounting flange on the engine to "custom" align the starters. And any replacement starters had to be carefully aligned upon installation.

In order to be sure the starter gear is in proper alignment with the flywheel gears, it is important to be sure that the starter is mounted in perfect alignment. Due to the difficulty, and knowledge and experience required to properly mount a starter, is is sometime best to have a Professional automotive Technician install a starter.