I have a 2007 G6 with the 3.5L, a few weeks ago I pulled the motor out due to it having various oil leaks. A lot of the motor was resealed with new gaskets except for the rear main seal due to it not leaking and being in good shape(flex plate was never removed). When we put the motor back in the engine ran great however, the starter wouldn't disengage and you can hear it spinning. We got a new starter thinking that maybe the solenoid was bad in the old one. The new starter that we got does the same thing. We checked the relays and that wasn't the problem. We pulled the starter off and when you would turn the key the starter would engage the gear would come out and it would go right back in when you let off. we started the car and pulled the signal wire off the starter after it started and it still didn't disengage. After that we thought that maybe the starter gear may somehow become too close to the flexplate so we tried the old trick of shimming the starter, this didn't fix the problem. After none of this worked we tried to reset the ECM and changed the ignition switch also with no luck. Has anyone had a problem like this or have any clue what could be going on?