Hot Rods 8" axles in a 9" ???

I have been told that the stock 28-spline axles out of a 8" rear end will swap into a 28-spline 9" rear as long as ALL the other parameters are the same...bearing size, lenght, etc......

Is this accurate?

 

Yes.

 

Yep, read this as it will show you that I used 8" axles to build a narow 9":



I am going to show the steps involved in narrowing a 9" Ford rear end housing. I am narrowing the following housing to accept Maverick 8" Ford 28 spline axles and housing ends to end up with a 56 3/8" wide 9" Ford rear end that will bolt in to a '65 Comet.

-First off, to clear up some mis-conceptions, a rear end is NEVER measured from backing plate to backing plate. That measurement tells you absolutely nothing because there are so many different backing plates, brake offsets and brake shoe widths. ALWAYS measure a rear end from the outside of the axle flange to the outside of the axle flange.

-Here are some terms, vital measurements and facts:
-28 spline 8" and 9" Ford axles are the same spline.
-You have to cut at least 4" out of 8" or 9" Ford OEM axles in order to shorten and re-spline them. Some of the older axles cannot be shortened at all. You cannot remove 1", 2", or 3" from any stock Ford 8" or 9" axle.

-Axles are always measured from the outside of the axle flange to the end of the splines.

-Brake offset is the measurement from the outside of the axle flange to the inside edge of the bearing retainer flange + 1/8". (the 1/8" is the thickness of the brake backing plate)

-Most small bearing 8" and 9" Fords have a 2 1/2" brake offset.

-Most big bearing 9" Fords have a 2 3/8" brake offset.

-These brake offsets are the most common, but there are always exceptions, so your best bet is to measure what you have.

-Centered pinion rear ends will ALWAYS have a left side axle that is 4" shorter than the right side axle.

-Rear ends that have the same length left and right side axles ALWAYS have the pinion offset 2" to the right.

-The "dogbone" is a tool that shows where the edge of the axles end up when bolted in the housing. It allows measurements to be taken with a bare housing when narrowing a housing.

-The space between the two axles is ALWAYS 1 1/8" on 8" and 9" Fords whether the rear end has an open diff, posi, locker, spool etc. This measurement is the same throughout all years of production.

The rear end housing that I will be using is from a late 60's early 70's Ford pickup. It is the small web housing, but it has 3" O.D. housing tubes that are .188" thick. It will handle lots of abuse:


I will be using the small bearing axle ends from the 8" rear end. They have already been cut off and faced in a lathe to 2 3/8" in length:


The 8" axles have a 2 1/2" brake offset:


The left side axle measures 25 5/8" from the outside of the flange to the end of the splines:


The right side axle measures 29 5/8" from the outside of the flange to the end of the splines:


Here is the housing after all the brackets were cut off and ground smooth. It has been cleaned with a stiff wire wheel:


The "dogbone" is placed on the housing studs for measurement:


-Now for some math to determine where to cut the housing:

-29 5/8" right side axle length minus the 2 1/2" brake offset minus the 2 3/8" length of the housing end = a 24 3/4" housing cut measurement.


So we set the housing on the chop saw table and we measure from the edge of the cut off wheel to the right side of the dogbone:



......and the end of the housing is cut:


-Now for some math for the left side:
25 5/8" left side axle length minus the 2 1/2" brake offset minus the 2 3/8" length of the housing end = a 20 3/4" housing cut measurement.

The housing is set on the chop saw table and we measure from the edge of the cut off wheel to the left side of the dogbone:


....and the housing is cut:


We now have a very narrow housing waiting for some housing ends to be welded on:


A dummy centersection is set up with aluminum mandrels in place of the bearings:


This is the 1 1/2" diameter stainless steel alignment bar that will slide into the centersection:


The centersection is bolted into the housing and the alignment bar is slid in place:


Another aluminum mandrel is used to place the housing end on the alignment bar. The face of the centersection is leveled and the bolt holes on the housing ends are also leveled. The housing end is tack welded in four places 90 degrees apart and then fully welded:



Here is the finished housing. When assembled, it will measure 56 3/8" wide, narrower than any 9" ever offered from the factory:

These terms, measurements and procedures can be used to narrow any 9" Ford housing to accept any length axle whether they are stock or aftermarket. Notice that we built a housing to utilize axles that were on hand, but we can also figure any housing width and determine what length axles to order for it using most the the measurements above along with a couple more.

 

yep..possible.

 

So, is that 4" shortening in total for an axle (2" a side?) or is that per side?

I need a set of axles for a 57' ford 9" rear.

 

4" per axle.

 

KOOL...thanks!!!

 

Excellent thread!!

 

We narrowed a Nine Inch rear 8"( 4" per side) , moved the short axle, which is 4 inches shorter, to the long side, and resplined the long axle after cutting it......