Having problems with the starter. replaced the starter and ring gear and the problem is starting agian after a week.sounds like the starter needs to be shimmed

Year/make/model?? Sounds like a worn flywheel/ring gear located inside at the back of the engine. The transmission will have to be removed to access this ring gear. However, it can be checked for damage by removing the starter and ( in some cases there is an inspection plate at the bottom of the transmission ) looking at the ring gear for damage to the teeth that the starter contacts to turn over the engine

Without being able to hear the sound it's hard to point you in the right direction without more details. My first assumption from what you've described would be that the noise is present only while cranking/initial starting. If this is so, there are a few possible reasons for this. 1. The starter that was put is is faulty. 2. The starter was incorrectly installed. (Some starters actually have an alignment and/or shims although it's uncommon on most cars.) 3. The starter that was installed was the incorrect starter for your vehicle. (A lot of vehicles have different starters for automatic and manual transmissions that'll look identical and bolt on but the throw of the starter gear is different and/or the gear's teeth on the starter is different and doesn't properly mesh with the ring gear. This will ruin the teeth on the ring gear on your flex plate/flywheel.) 4. The teeth on the ring gear of your flex plate/flywheel were previously worn because of your old starter and now the teeh on the starter gear are not properly meshing. (This will ruin any starter that you put in.)

Hope this helps. If you can provide any more information, I'd be happy to help you to further narrow down the problem. e.g. Year, make, model, engine size, transmission type of the vehicle and part number of the starter installed. A better description of the noise and conditions of occurrence. e.g. A rough grinding noise while holding the key in the start position followed by a hollow metallic pinging noise or prolonged whining. Etc.

If you had a flywheel replaced it is possible that it is not reinstalled properly. Check for engine vibration at idle . Check that the starter is in correctly. IT appears that the starter pinion is not meshing correctly with the ring gear and that is your noise . It goes after starting because the pinion disengages from the ring gear. The problem is a misalignment between the pin ion and the flywheel ring gear ( nothing at all about polished gears ). IT is all in the installation of the flywheel -starter and gear box.

The starter is not engaging with the flywheel, sounds like teeth missing on starter ring gear, when you move the car in gear, you are turning the engine, so repositioning the ring gear and then it starts. The starter needs to come off and inspect the gear on the pinion and you should be able to see the ring gear through the starter mounting hole, (you will have to turn engine to see all of it). If it is a worn ring gear, it's gearbox out and a new flywheel. Good Luck.

Your starter motor needs to be replaced, also your ring gear could be damages as well. (ring gear is the part that has teeth on it and so does your starter drive they mesh together to start or turn the engine over so it can start)

I would reccomend to remove the starter and check the teeth on the flywheel and make sure that the ring gear is still attached to the flywheel. You may find the starter loose when you go to remove it but I would still check the teeth on the flywheel!

Sounds like your starter is slow to disengage , but I would check with someone who is handy with cars , not necessarily a mechanic , just someone who can confirm your assessment and my suspicion. If that's the case , you might have to replace the starter. This problem could damage the ring gear on the engine which would be a lot of $ to have replaced.

eathier it needs shims or you have a bad flywheel sounds like its free spinning at times pull the starter an turn the ring gear make sure its not missing teeth if not you may need shims

When you try to start it now, does the starter motor run or is there no sound at all. If you can hear it running or spinning freely but not cranking the engine, you will have to repair the starter motor. (most probably a bendix replacement)
If there is grinding or loud clicking you will have to replace the bendix and repair the ring gear. (the ring gear can be repaired in place if it can be reached with a dremel.)
If there is no sound you will have to check the start circuit by firstly activating the starter by connecting a battery positive (+) charge to the solenoid start terminal on the starter and work your way back to the start relay, Neutral switch and ignition switch.
If you have no electrical experience, an auto electrician or mechanic should be able to solve the problem easily.
Hope this will help you.

There may also be a loose bolt head scraping on your flex plate if you have an automatic transmission.