Yes there is a problem with ring gears on the 39x range this has started to occur since the starter motor was moved to the other side of the bellhousing to allow for better access.
If you contact Linde the original part numbers should change to a tougher ring gear and a starter motor with a fitting kit that will modify the spacing between motor and bellhousing.
I have had a 391 ring gear last 2 months between changes,I fitted the kit and all seems well..
cheers
herald.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.