9 yrs later and still a great post. I just followed instructions--glad pics still there...

 

Oh my goodness, the fire has been lit again! I have some discretionary funds this year and have always wanted to change the rear gears to the optional 3:55 gear set from the 3:31 set and add the Ford Racing Diff Cover, like on my previous '98. Car has just under 26k miles and I still have the Superchips handheld tuner that came with the car. I seem to recall something in the menu about 'gear ratios' - hoping that will correct the speedo.

Car will have its upcoming annual service (rarely drive 3+k miles per year); still needs its RH airbag replaced, state inspection and I'm thinking about having the stock tune checked to see if its the latest and greatest. Same goes for my Superchips tuner as its one of the first released for the '05 model. I'm a bit leery about this last item as my bike dealer downloaded the most recent tune for my '08 motorcycle last year. While it doesn't run bad, I seem to think it ran slightly better before!

My grown daughter wants the car but a new '18 GT well equipped is around $50k I've read so that's out of the question at the moment.

 

Well, I just did the job on my '05, I used "YouTube" as my guide, didn't see your/this article for some reason. At 74 years of age, not a walk in the park. Sadly my wallet is not full of green stuff. And my get up and go has been short on appearances for quite some time.

FWIW, here in NC I found that Advanced Auto had a gasket and I used that Black stuff in the original posting on it with the plan being that I did not want to do it again! I also went with Mobil 1 LS 75W-140 with "Limited Slip" built in. I used a suction pump to put the gear oil into the differential. (I wanted to suction it out, but couldn't make it happen, gave up, cursed and took off cover)

Incidentally, my younger, by some 15 years, brother is a gear head big time. Has had somewhere in the range of near 200 cars in his lifetime. Wanted me to go with cover off method to check for shavings inside. Sad truth is I did this at 94k miles., somewhat past the 60k discussed. Just couldn't get myself to do it. I've already done my 5-Speed two times for sure, and I have the Mobil 1 ATF in the garage awaiting a stroke of ambition. I bought it before the gear oil, all a sudden I decided to do the differential. For the record, I found no debris in the diff, the fluid looked quite nice, my brother said something about smell, mine did not any "stink" to it. I think maybe, maybe, that is becasue I"m not shy on the throttle, but, i'm not burn out and pop the clutch type of guy.

 

I just finished this. Do yourself a favor and get a pump to pump the new fluid in.