I have my 2013 Mustangs MT82 apart on my garage floor. The motivation for this was the slow loss of the 5th gear synchro. I now have that crunchy nugget in my hand. When I look up the BR3Z 7107 I find two different parts, an E and an F. The E is the standard sintered surface synchro and the F is a graphite faced synchro. The one in my car is the F version. Can anyone tell me why these were made different and which applications the E version is for. All other synchros I have taken out are sintered - I have not had to remove 6th gear so do not know about it. Thanks for any help.