differential

[alltin33]

 Do all 57s have 9 inch differentials?

[Ford Blue blood]

Yes, except the trucks.

[lalessi1]

Yes. The rear end was a new design for 1957. It moved the pinion gear down in the carrier to lower the driveshaft. This allowed a lower tunnel/floor allowing a lower design for the car. It also dramatically increased the strength of the rear end. "Longer, lower, and wider" design theme for the first time.

[hiball3985]

Yes, except the trucks.

57 and up 1/2 ton F100 had the 9" also, housing was different but the 3rd member was the same.  F250 had Dana..

[Ecode70D]

57 and up 1/2 ton F100 had the 9" also, housing was different but the 3rd member was the same.  F250 had Dana..

X2 What Jim stated.  I like them so much better than the Dana.

[Ford Blue blood]

Yup, you guys are correct.  Forgot, my 73 had a "N" 9" in it, the 48 was a Dana.

[brushwolf]

How far into the 60's was the nine inch used on all full size Ford cars?  I have 57's, 58's, 61's, 63, 76 and every last one had a 9 inch, no matter whether a 6 cy or 8 cyl. Granted most were either Y block or FE motors, but I have a base model 61 stripper 4 door with a 6 cyl that is also a nine inch. The only variant to that I have noticed was the 8 inch in Fairlane and Torino in some smaller cars with small motors getting the 8 inch instead. So, there were many years where a 9 inch will be found in virtually every full size Ford, not just 57's...

[RICH MUISE]

9" in later models, yes, but some are wider than our '57s.

[hiball3985]

9" in later models, yes, but some are wider than our '57s.

Rich I think he was asking about the 3rd member, I maybe wrong. So yes the axle housings are all over the place depending on year. The 3rd members are mostly interchangeable except some models used a different axle spline count. Just as a note the 57 3rd member was a one year only design but you can use a later one. Not sure when the design changed? Mid/late 57 or not until 58. 

[brushwolf]

Yep, "differential" to me means the gear carrier and its components when the topic is a Ford 8" or 9". Probably means different things to different people, but I replied on that basis because the OP had used that terminology, differential rather than axle.  If we were talking about an 8.8 differential I would however be inclined to think "differential" ="whole axle" cuz no dropout carrier. Just how I refer to them.

[59meteor]

Ford did install an integral style rear axle assembly, in full sized cars, with a cast center casting and a sheet metal cover, similar to a 10 or 12 bolt Chevy, or 7 1/2 or 8.8 later Ford. Not sure when they started using them, but I know a guy with a 69 Galaxie with one. I believe they were called an 8 1/2". Ford also used a 9 3/8" "drop out" , similar to a 9", but slightly larger, yet weaker at the same time. The 9 3/8" was commonly used in big Fords, Thunderbirds and Lincolns. Every one that I have seen was 31 spline, and often had a limited slip unit, but only with tall gear ratios, often 2.80 or 3.00. The 9 3/8" 3rd member will fit into a 9" housing, if you notch the housings gasket flange to allow the larger ring gear to fit. But with the weaker casting, and limited ratio selection, not much reason to.                                                          As for swapping different 9" center sections, in addition to 28 vs 31 spline, other things to keep in mind are some cases have a filler plug for checking and adding gear oil, but some housings had the plug in them, so they are lacking a fill plug in the cast case. So you could potentially have 2 points to add fluid, or none. Also, Ford used a wide variety of driveshaft pinion flange yokes, with different sized U joint cup diameters, widths, and U bolt sizes, as well as a number of different flange lengths.

[hiball3985]

Lots of good points made about the differences. I had to use one without the filler hole one time years ago and required adding the lube through the axle tube before installing the axle and with the car jacket up higher on one side 

[Rancher]

Yup, I learned  the fill location lesson  long ago.
I believe '60-up was the change.

I suppose the vent or a removed stud's location could be used as fill point also?

[alvin stadel]

Jim, about 25 years ago I had to fill my diff. the same way. Pulled the axle and put in correct amount of oil, and am still driving it today. Never has leaked so I guess it is still ok.

[mustang6984]

  Put the car on a rotisserie...flip it over...fill the diff via the drain plug...flip it back...drive on. 

Just kidding...my mind is a bit warped today...okay...EVERY day...but I had to it out today!