My original starter would always spin when the key was turned to the start position, but began to intermittantly fail to engage the flywheel after being on the car three years. There was no gear clash, but the starter would just spin freely and not engage the starter pinion to the flywheel. (The flywheel is not missing any teeth). I removed the starter and it bech tested OK but would only work properly, intermittintaly when installed. Since it was under warranty, I tried two rebuilds and neither one would work at all. Yes, they were shimmed properly. I got my original starter back and disassembled and cleaned the selonoid and reinstalled it but it still will intermittantly fail to engage the pinion gear to the flywheel. I've been replacing GM starters for 20 years and I never had such trouble. The pinion gear slides up and down the shaft smoothly without binding. What would you do next? I am thinking of trying a new solenoid. Does that sound like it is worth a shot? Any and all other suggestion are welcome!

 

I have the same problem with my 87 firebird it'll do the same, run on and run on then it'll catch,a mechanic told me that youmight have to put some washers under the outside bolt as so to tilt the starter up to the fly wheel but I'm a little scared too.
Vance

 

It sounds like it could be the starter drive. Theres a one way clutch right behind the gear in the starter. Sometimes when they go bad the gear actually engages the flywheel but the clutch just freewheels. You should be able to get a new starter drive from any parts store. I know we have them at napa.

 

I guess if you want anything done right, you have to do it yourself. After I found that the two NAPA rebuilt starters were no good, I went and bought a new solenoid and starter gear drive and rebuilt the original starter myself and it now works as good as new. The parts totaled less than $20. Thanks for the suggestion on the starter gear drive, chevymad. Since I installed both the new solenoid and the starter gear drive at the same time, I'm not sure which one really fixed it but I figured I'd do both since it was out of the car. Thanks again for the help and suggestions.