I inherited my sons 2002 GT after he passed away and tried driving it and it ran ok till I tried to put it in 3rd or 4th gear, would not go in, what could cause this ? I am assuming the synchros are bad but was wondering if there could be something else I could check before pulling the trans. The car will go in 3rd or 4th from a stop but not after it is spinning, that is why I assume the synchros are bad. I am a Foxbody owner since 1989 and dont know much about this style Mustang or the TR-3650 trans. Thanks.