Topic: 65 vs 66 Hinge bolt size

[MustangAndFairlane1867]

The passenger door on my Rangoon red 1965 fastback with black interior is not original to the car, most likely replaced by a previous owner after some collision or rust damage to the original door.  I know this one is not original because the jams are white and the interior side of the door is a light blue.  But the interesting thing I discovered yesterday is that the bolts that attach the door hinge to the door are 5/16" while the bolts on my stock/original driver-side door are 3/8".  Both with coarse threads.  And another point of interest--all the bolts on both sides of the car that attach the hinges to the A pillars are also 3/8" coarse threads.  My first thought is that maybe Ford went to a 5/16" door bolt in 1966 and that my passenger door is, in fact, from a 1966 Mustang.  My car has a February build date and the code stamped on the original driver's door appears to be "2 1 2B" while the stamped code on the "mystery" passenger door appears to be "11 4 W3."  There are no cosmetic or mechanical issues with the "mystery" door--it looks and fits fine--but I'm curious if anyone else has noticed this difference in the hinge-bolt thread size between 1965 and 1966.  Or is there a different explanation for this apparent anomaly?    Thanks, Ron.

[carlite65]

i have know about that anomaly for years. have no idea why the switch.

[J_Speegle]

Typical and expected between the production periods.  Never met an engineer from the years leading up to 65-66 to ask thwe question and it would be likely they would not have worked on that particular detail

[MustangAndFairlane1867]

Thanks, guys.  The anomaly bugged me so much I drilled and tapped the five 5/16" holes to the 1965-correct 3/8" coarse size.  All is good now.  All planets are aligned.  Lol.  Ron...

[jwc66k]

Ron,
You might take a few minutes and look in the library under "Mustang Hardware Spreadsheets 64-66" where you will find two files, one by Ford part number and the second by Application/Location. In that file under "Door Hinge-Body" and "Door Hinge-Door" there are two different sizes referenced, the 3/8-16 bolt for 64 and 65, and 5/16-18 for 66. Give it a try. There are over 3,000 entries.
Jim