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Old 08-26-2009, 08:07 PM   #1
Drive Em
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Default How To Narrow A 9 Inch Ford Rear End Housing:

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.

Last edited by Drive Em; 08-26-2009 at 10:39 PM.
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Old 08-26-2009, 08:13 PM   #2
RPM
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Very nice. Do you weld on all the brackets before you weld the ends in? I know on this one there were just 2 saddles.
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Old 08-26-2009, 08:20 PM   #3
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

awesome post man ,not as hard as one would think.Not saying its ez at all thanx for the post
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Old 08-26-2009, 08:20 PM   #4
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Quote:
Originally Posted by RPM View Post
Very nice. Do you weld on all the brackets before you weld the ends in? I know on this one there were just 2 saddles.
If it is just two leaf spring saddles, yes I will weld the housing ends on first, and then check the housing for warpage and correct it if needed. I omitted the straightening of the housing process that goes along with the narrowing process because I am going to do a separate "Straighteneing A 9" Housing" article in a day or so. If the housing will receive many brackets, I will weld the housing ends on last, but I will straighten the housing before I do. 9 out of 10 housings I work on are bent on at least one tube.
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Old 08-26-2009, 08:47 PM   #5
55 dude
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

ROCK ON DUDE! really enjoy these kinds of write ups and pic's were great! what do those "dogbone gauges" set someone back? looking foward to part 2. is it next week yet?
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Old 08-26-2009, 09:00 PM   #6
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

i went back and reread parts. when you stated that you leveled the center section did you mean you rolled the housing until the "flat" on the dummy 3rd member was level. and also you stated the bolt holes on the housing ends were leveled. my confusion was with the next picture stating housing was done as it looked like housing ends flats were 90 deg. turned from face of dummy 3rd member. not being critical just for personal clairifacation. thanks!
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Old 08-26-2009, 09:04 PM   #7
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Quote:
Originally Posted by 55 dude View Post
i went back and reread parts. when you stated that you leveled the center section did you mean you rolled the housing until the "flat" on the dummy 3rd member was level. and also you stated the bolt holes on the housing ends were leveled. my confusion was with the next picture stating housing was done as it looked like housing ends flats were 90 deg. turned from face of dummy 3rd member. not being critical just for personal clairifacation. thanks!
I inserted text where it should not have been, it is now corrected. The flat is perpendicular level, as well as the bolt holes. It really does not matter where the holes on the housing ends end up, but I like to keep everything perpendicular.
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Old 08-26-2009, 09:05 PM   #8
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

I often wondered how the end flanges were properly placed before being welded into position. Please elaborate!
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Old 08-26-2009, 09:08 PM   #9
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Quote:
Originally Posted by 55 dude View Post
ROCK ON DUDE! really enjoy these kinds of write ups and pic's were great! what do those "dogbone gauges" set someone back? looking foward to part 2. is it next week yet?
The dogbone is about $30.00 from Dutchman. I will try to do the "Straightening a 9" Housing" article Thursday.
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Old 08-26-2009, 09:10 PM   #10
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Quote:
Originally Posted by Ratmotor View Post
I often wondered how the end flanges were properly placed before being welded into position. Please elaborate!
I place the flat on the front of the centersection perpendicular and level, and then I level the edge of the bolt holes on the housing ends before welding.
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Old 08-26-2009, 09:20 PM   #11
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

I get it now....thanks!
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Old 08-26-2009, 09:20 PM   #12
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

thanx, great read, just as i need to shorten mine by 2 inches.
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Old 08-26-2009, 09:36 PM   #13
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

So the 28 spline 8 inch axles will work in a 9 inch 28 spline pumkin? THANKS JOHN
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Old 08-26-2009, 09:40 PM   #14
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Quote:
Originally Posted by porkshop View Post
So the 28 spline 8 inch axles will work in a 9 inch 28 spline pumkin? THANKS JOHN
Yep, same spline.
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Old 08-26-2009, 09:49 PM   #15
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Great info!
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Old 08-27-2009, 08:59 AM   #16
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Bump for the morning crew.
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Old 08-27-2009, 04:35 PM   #17
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

nice tech article i enjoyed your thread , well done
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Old 08-27-2009, 06:11 PM   #18
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Great tech info,thanks for posting.
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Old 08-27-2009, 06:20 PM   #19
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Don't you measure the brake offset to the outside face of the axle flange? Looks like more than 2-1/2" of actual offset in that pic.

Great article, just nitpicking

granny

Last edited by granny; 08-27-2009 at 06:28 PM.
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Old 08-27-2009, 06:42 PM   #20
Drive Em
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Default Re: How To Narrow A 9 Inch Ford Rear End Housing:

Quote:
Originally Posted by granny View Post
Don't you measure the brake offset to the outside face of the axle flange? Looks like more than 2-1/2" of actual offset in that pic.

Great article, just nitpicking

granny
The measurement is to the outside face of the axle flange, it must be the angle of the picture.
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