just swapped out my usdm engine with a jdm and noticed some play side to side on the ring gear of my 8.5lb fidanza fly wheel. it doesn't seem to slip. car seems to run fine...

according to fidanza they said if the engine over heats or gets too hot, it can cause the ring gear and flywheel to separate due to the heat expansion... before the engine was swapped, it never really overheated.

without a rattle from the flywheel how pressing do you think this problem is and has this happened to anyone else? I read a few posts on the ring gears being installed backwards but this is a bit different...

 

if Fidanza says that is normal, i think -> dont care

 

That expansion excuse doesn't sound right. Aluminum expands more than steel when warmed up, so that ring gear would get tighter.

In answer to your question, what is keeping the ring gear in place? If it can't come all the way off it will probably be ok for a while, but if it's moving around it will only wear against the aluminum and get looser.

 

Thats quite odd. Mine doesn't move side to side at all. I would feel unsafe at this point.