Did you shim the starter closer or farther away? You can move the starter closeror farther away by the placement of the shims. You need to check the gap between the bendix and flywheels gears. A paper clip is about the right amount of clearance between the gears.
Important: Most GM pad-mounted starters prematurely fail as a result of improper shimming, regardless of whether the old starter had shims or not, you must inspect the clearance of the new unit as it may or may not require shimming.
Before Installation: You must understand the need for proper starter to flywheel clearance. This “clearance” is critical to avoid damage to Flywheel, Starter Drive and Battery.
Why Shimming Varies:
1. Mounting pad tolerances and hole locations vary from block to block, this moves the starter drive gear away from the flywheel varying distances.
2. The mounting pad on the engine block dimensions vary. This also moves the starter drive gear away from the flywheel varying distances.
Step1 - Inspection: Remove lower flywheel housing cover and examine the entire flywheel for visual problems. (Worn, chipped or broken teeth; bent flywheel and/or incorrectly cut teeth)
Step 2 - Check Clearance: Insert a screwdriver behind the starter drive. Move starter drive assembly out toward flywheel so that starter pinion and ring gear teeth mesh.
Step 3 - Measure Clearance: Center the pinion tooth. Check clearance (looking for .025” - .060”). A convenient plug gauge is a common paper clip, which typically measures approximately .035”. Important - Check at least 3 ring gear locations 120o apart for proper clearance. Shim as required
at minimum clearance location. After measuring clearance, push starter drive back into original position.
Step 4 - Proper Shimming: To increase clearance: Use entire shim across both holes. .015” shim increases clearance approximately .0075”. This moves the starter down and out, away from the flywheel (use no more than 6 shims). To decrease clearance: Use 1/2 shim only on the outer mounting bolt hole from oil pan. This moves the starter in and toward the flywheel. .015” shim decreases clearance approximately .010”