         
Broken Starter Housings Starters are not capable of developing sufficient torque to damage drive end housings. The only force great enough to do this while the starter is installed is the engine itself by way of the ring gear. 1. The major cause of broken drive-end housings on starters is due to too small a clearance. If the clearance cannot be measured, it is best to put a shim between the engine block and the starter than to leave one out and chance breaking a drive-end housing. If the clearance is excessive (0.060 in. or more) and there are not shims under the starter, the starter clearance can be reduced by shimming under only the outboard starter mounting bolt. A 0.015 in. shim used under the outboard mounting bolt will decrease the clearance by approximately 0.010 in. 2. A false start can lead to serious drive end housing damage. An engine will normally rock back when it stops, particularly high compression engines. If the drive gear of the starter is re-engaged at the same moment that the engine rocks back, serious damage may be done to the drive gear, the drive end housing, or both. 3. Engine backfire can also cause the engine to rock back, which can result in the same damage as described above. Common causes of backfire include pre-ignition and advanced ignition timing. 4. Improper starter installation can’t cause the engine to rock back, but if mounting bolts are not properly tightened or if there is foreign matter between the drive end housing and its mounting surface, the same type of damage could occur. 5. Improper tolerance between the flywheel or ring gear and the starter drive gear is a common cause of starter damage. The tolerance between flywheel and starter on GM vehicles with pad mount starters (bolts go into engine block) can be increased by using one or more shims, but it is always good to check and make sure that the starter you are installing is right for the application. 
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