What rear axle bearing size do I have?

DK832 · Nov 15, 2006

I'm not sure if I can determine my 9" rear ends bearing size without pulling an axle out? I was told that the bolts for the bearing retainer plate (is that the right English term?) are different? Any help plz?

D.Hearne · Nov 15, 2006

What car did the 9" come from? Or is it original to your car?

ultrastang · Nov 15, 2006

DK832 said:
I'm not sure if I can determine my 9" rear ends bearing size without pulling an axle out? I was told that the bolts for the bearing retainer plate (is that the right English term?) are different? Any help plz?

An easy wat to tell would be to remove the drum from the brake assembly. You will be able then to see the (4) retaing nuts that holds the backing plate to the housing's end flange.

A small bearing rear end will require a 9/16" socket to break the (4) nuts loose. (3/8" diameter flange bolts).

A large bearing rear end will require a 3/4" socket to break the (4) nuts loose. (1/2" diameter flange bolts).

chepsk8 · Nov 15, 2006

To my knowlege, it depends on the axle size. The 28 spline axles were smaller in Diameter, and the 31 were thicker.

I had two pumpkins for the SCJ, the original 3.91 N 31 spline, and a 3.25 28 spline posi. Every time I changed, I had to swap axles & seals as well!

D.Hearne · Nov 15, 2006

You're both half right. There are large bearing retainers that use the smaller bolts, and both small and large bearing 28 spline axles.

Edbert · Nov 15, 2006

Axles would only affect the inner dimension of a bearing not the outer. Ford only made the two, large and small. Large came only on trucks (E-series/F-series/Bronco) and full-size (Galaxie not Fairlane) vehicles. ALL mustangs had small bearing 9s, of course your rear could have been swapped over the last ~40 years, so there's no subsitute for measuring.

ultrastang · Nov 15, 2006

Edbert said:
Axles would only affect the inner dimension of a bearing not the outer. Ford only made the two, large and small. Large came only on trucks (E-series/F-series/Bronco) and full-size (Galaxie not Fairlane) vehicles. ALL mustangs had small bearing 9s, of course your rear could have been swapped over the last ~40 years, so there's no subsitute for measuring.

I recognize that photo. It's from my website. --(Large axle bearing 9-inch housing on left from a '60 T-Bird . Small bearing 9-inch housing on right from a '59 Fairlane).

All 8-inch rears have small axle bearings with 3/8" diameter retaining bolts.

Small bearing 9-inch rears also have 3/8" diameter flange bolts.

Large bearing 9-inch rear ends have 1/2" diameter end flange bolts. --With two possible exceptions --the later "Torino-style" large bearing rear ends have 3/8" diameter flange bolts, and SOME Versailles have 3/8" flange bolts even though the bearing size is large.

www.ultrastang.com

Edbert · Nov 15, 2006

ultrastang said:
I recognize that photo. It's from my website. --(Large axle bearing 9-inch housing on left from a '60 T-Bird . Small bearing 9-inch housing on right from a '59 Fairlane).

Hope you don't mind! I'm sure I am one of a few thousand who have that bookmarked. Here's the full link http://www.ultrastang.com/Rearinfo.asp?Page_ID=1

The caption says the one on the left is from a '57 station wagon.

ultrastang · Nov 15, 2006

Edbert said:
Hope you don't mind! I'm sure I am one of a few thousand who have that bookmarked. Here's the full link http://www.ultrastang.com/Rearinfo.asp?Page_ID=1

The caption says the one on the left is from a '57 station wagon.

No, I don't mind you posting the picture.

...Hmmm, I've had a number of late 50's Ford rear end housings over the years. I was thinking that was the '60 T-bird hosuing I have, but it could have been one of the 9-inch station wagon large bearing housings I had at one time or another.

In back ground, some of the "goodies" in my shop: '60 T-Bird large bearing 9-inch housing, what's left of a '59 Fairlane 9-inch small bearing rear end housing, in floor --'79 Versailles 9-inch disc brake rear end, [near press]; 4-pinion Traction-Lok differential, [near drill press] Ford 9-inch N-case 3rd member with 4-pinion Traction-Lok diff and 3.50:1 gears.

http://img169.imageshack.us/img169/523/68mustang006of2.jpg

www.ultrastang.com

DK832 · Nov 16, 2006

Thanks everybody. Sounds like the safest way is to take the rear apart and measure to be sure, then order the correct Cobra brake brackets from Steve. I have no idea where the 9" came from, it was not born with it. I was just very ready to order, as the calipers and rotors arrived yesterday!

I'll be removing the rearend alltogether as soon as I have a free weekend, as I'm installing new 5-leafs, Detroit TrueTrac, Comp Engineering Slider bars, HD shackles wit poly bushings and Cobra brakes.

Nikosia01 · Jul 29, 2019

Hello everyone. please help me. I have 1966 mustang 6 cylinder end I want to put discs back but everywhere I'm wondering if I have small or large bearing. I have 7 1/4 rear axles and I do not know what it is. small or large? does anyone know? thank you.

Edbert · Jul 29, 2019

Nikosia,

I do not think large bearings came on the 7.5 or the 8.0, only the 9.0 had them.

Nikosia01 · Jul 29, 2019

DK832 said:
I'm not sure if I can determine my 9" rear ends bearing size without pulling an axle out? I was told that the bolts for the bearing retainer plate (is that the right English term?) are different? Any help plz?

my car definitely has the original rear axle 7 1/4 that's what I saw in VIN number. I read that there were not many. when I removed the rear axle I saw that it has 24 splines.

What rear axle bearing size do I have?

DK832

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