If I were to go looking for a truck that was very likely to have 31 spline axles just what trucks or axle code would I be looking for?

 

As far as I can tell there is no 100% way to say this truck will and that truck won't have 31spl axles. BUT with that said if I was going looking I would look at 4x4s first and later models since in my own personal experience the only 28 spl I have had was early (as in before 74) 2wd, all the 4x4s I have owned EXCEPT a 73 had 31spl (and I won't say that 73 was original since it had a real 390 in it, as well as some other stuff that didn't fit for being original equipment)

You might also look at the early 80s too that still had the 9" I have the axles from one in my garage and they are 31spl and I know the housing was identical to the one I took out of a 77 and honestly I wouldn't be able to tell you which axles came from that 81 compared to the 77 and the 79 axles that are also sitting out there.

 

That's good to know as there are lot's of 80's truck around!

 

I agree start witht the 4X4's first.

 

are you talking the entire rear axle housing and all..

or just shafts.

There is only one 31 spline axle shaft that will fit a 28 spline housing, and it's rather rare in the wild.

 

I was planning on just swapping axle's

 

Do 4X4's and 2X4's have different length axles?

 

F100/150.

The rear axle has nothing to do with 4WD.

Some 1973/79's have 28 spline axles, some have 31 spline axles.

The only way to know without pulling the axle is by the Ford ID tag number.

And the ID number must be translated, the axle shaft spline count isn't listed on the tag.

All that will be listed is either WDM or similar, and/or D4TA-AA or similar.

The ratio will also be listed. If L/S is present, the ratio will be, for example: 3L55. If no L/S: 3.55.

The AXLE code on the Warranty Plate when translated only gives the ratio and whether it has Limited Slip (L/S) or not.

If the AXLE code on the Warranty Plate begins with a letter, it has L/S, if a number, it does not.

 

Thank's Bill!!

 

The problem is, in my travels, I've seen 3 different 9" axles.

28 spline - Uses a sealed bearing

31 spline #1 - Uses a sealed bearing

31 spline #2 - uses a non sealed taper bearing.


If you have 28 splines now, you need 31 spline #1.

 

First use of the tapered axle bearing: 1974 = D4AZ-1225-A.

And like the 28/31 splined axleshafts, not all 9 inchers used it.

 

How is a tapered bearing going to fit in a housing meant for sealed? The OD's are different.