Why the starter motor pinion position is important

Unlike with most alternators, starter motors can have a difference between manual and automatic.

What causes the difference

Unlike most alternators, Starter identification can be further complicated by different starters for Auto and Manual Vehicles. This is mostly but not always a difference in the position of the pinion or what is commonly called "Pinion at Rest" or "Out of Mesh Clearance". The Pinion at Rest measurement is used in finding Out of Mesh Clearance.

Pay attention to these two

Pinion at Rest is the measurement from the front mounting face of the starter motor where it mounts onto the flywheel housing to the leading edge of the drive pinion. This is important when we want to look at where the pinion sits in relation to the ring gear on the vehicle. Too close and there is a risk of the pinion hitting the ring gear or worse - staying engaged with the ring gear and destroying the starter. Too far away and the drive will not engage deep enough into the ring gear possibly damaging the ring gear and/or pinion.

Out of Mesh clearance is achieved using the pinion at rest measurement and taking that measurement from a second measurement taken on the engine from the mounting face where the starter bolts on to the ring gear, the difference gives us the out of mesh clearance between the pinion and ring gear.