Tech Bulletins

Flywheel Housing Spacer

Figure 1: Spacer
Figure 2: Spacer on Starter

Be sure to follow proper safety techniques as outlined by your shop or employer. This includes wearing safety glasses and gloves at all times, and disconnecting the vehicle’s batteries during any repair of the starting system.

The components listed below may continue to have power supplied to them even when the ignition switch is off. Use extreme caution at all times.

Disconnect the vehicle’s batteries before any service to the starting system.

Background & General Description

All Mitsubishi Electric 105P55 starters adhere to SAE standards which stipulate proper pinion travel distances for starters with SAE types 1 and 3 mountings. Some medium-and heavy-duty engines which use these mountings require the use of a spacer (Figure 1) between the starter and the flywheel housing’s starter mounting flange to maintain proper distance between the starter’s pinion & engine’s ring gear.

When to Use a Starter Spacer

The spacer is a part of the flywheel housing assembly and is specified by the engine manufacturer. It is NOT a part of the starter assembly. When replacing the starter on an engine which uses a spacer, the spacer MUSTbe re-installed between the new starter and flywheel housing to ensure proper clearance between the starter’s pinion and engine’s ring gear.

Common Problems

Spacers will frequently remain stuck on the starter being replaced (Figure 2). Carefully examine the old starter once it has been removed.

Failure to use a spacer when required by the engine manufacturer will lead to damage of the starter, ring gear or both.

Proper Spacer Selection

Re-use the spacer which was between the original starter & flywheel housing. If you are in question about the need for a spacer or need to replace a damaged spacer, consult the engine’s manufacturer.

Tech Bulletins