I have a 66 F100 with an 240 six cylinder and I decided to replace the pinion seal. The parts store gave me the correct part number 5778 but it doesn’t fit. I don’t know what to do to find the correct pinion especially since I have already taken the old one out. Any suggestions?

 

If you didn’t destroy the old one taking it out, take it to a good parts store and they Should be able to measure it with micrometers and match it with one. I use NAPA for things like that. If you still have the tag on the rear end get those numbers as well they may help also

 

What rear axle does it have? 9" .. Dana 44, Dana 60.2 or Dana 60.3?

The Dana's have an inspection cover, the 9 does not. The Dana's also have Limited Slip, the 9 did not until 1968.

If the auto parts sold you a 9" pinion seal and it doesn't fit, they sold you the wrong seal...because it's basically the SAME 1957/87!

3.00" O.D. x 1 13/16" I.D. // Ford changed the looks of the seal several times, so it will not resemble the original.

Last year the 9 was installed in Passenger Cars was 1980 (Lincoln Versailles). Last year for these: 1986 F150 & Bronco, 1987 E150.

 

I ended up going to my local NAPA store and taking my old seal. After some research they came out with the exact match. I’m thankful for those old stores that don’t just look on the computer for the first part that comes up. Thanks for your input.