9 Inch Diff…….Help!

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LloydT
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Joined: Tue Jul 14, 2015 11:26 am

9 Inch Diff…….Help!

Post by LloydT »

Ok this is for all the diff gurus, of which I am not.

I have a diff which was sold to me as a 9 inch diff. I have checked all the dimensions and identified that it is a Big Ford “Old style” it has 28 spline axles which are 30.1 inches or 767mm long.

I want to convert to disc brakes, but my axle backspace is 2 inches or 52.25mm. I cannot for the life of me find disc brakes anywhere that suit a 2 inch backspace they are all 2.36 or 2.5 inch. Is a 2 inch backspace factory or is it likely it has been altered.

It’s doing my head in :shock:

Does anyone have any suggestions?

Lloyd.
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zuffen
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Joined: Fri Jan 28, 2011 7:45 pm
Location: Sydney

Re: 9 Inch Diff…….Help!

Post by zuffen »

Photos would help us see what your describing or even a sketch a with some dimensions.

The slight backspace difference may only mean the calliper mount has to in a slightly different spot but you would most likely making them anyway so easy to sort.

Keep us posted and we'll do our best to help.
Never argue with an idiot, they will drag you down to their level and beat you with experience.
Greg N Smith
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Re: 9 Inch Diff…….Help!

Post by Greg N Smith »

This may help -

https://www.strangeengineering.net/wp-c ... r-Form.pdf

I expect you are talking about Dimension F which Strange call Axle Offset (Brake Gap)

Shows common Ford 2.145 - 2.3326- 2.500 - 2.625 and GM (USA) 2.8325

Photo would help and Good Luck - I am doing similar today
LloydT
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Joined: Tue Jul 14, 2015 11:26 am

Re: 9 Inch Diff…….Help!

Post by LloydT »

This is the offset I'm referring to.
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zuffen
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Re: 9 Inch Diff…….Help!

Post by zuffen »

In your first photo what is the piece of steel you're measuring off? It doesn't look like it's part of the axle or calliper mount.

Could the diff be out of a Cadillac? They had odd brakes and bearings, if my memory serves me right.

To solve the spacing just make the calliper mount fit the dimensions you need.

That's real Hot Rodding!
Never argue with an idiot, they will drag you down to their level and beat you with experience.
LloydT
Posts: 6
Joined: Tue Jul 14, 2015 11:26 am

Re: 9 Inch Diff…….Help!

Post by LloydT »

Thanks Zuffen,

The measuring picture is just a pair of vice grips holding a steel ruler to give me something to measure from.

It’s my first build and I’m just trying to keep things within my abilities :lol: :lol:
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Sudsy
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Re: 9 Inch Diff…….Help!

Post by Sudsy »

Just get one of the discs you mentioned and mount the caliper to suit. If you get a solid disc use Skyline calipers with the handbrake integrated. They are the same as the fraud ones but easier to mount
Regards Bob
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FRANK BASILE
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Re: 9 Inch Diff…….Help!

Post by FRANK BASILE »

To help this, go to the DBA website. And get the disc catalogue . They have a download. You can look up by make as it is in alphabetical order, they list the rotor specs Diam/thickness/hole center/ and offsets from hub to rotor inner face. Ford had variances in the latter. Other vehicles with the same bolt pattern can also be researched. Such as Mitsubishi Magna having Ford. Many years back. Harcourt motor wreckers in Vic. Had a caliper bracket available to weld to 8" diff axle tubes inboard of the flange. These used Nissan Skyline Pintara calipers. And Commodore rear rotors you had to re drill. So with some research using another critical measurement. Thickness to match what the caliper donor vehicle had with it's rotor. And the axle center hole diam. You can select a rotor with similar spec and make your own brackets out of MDF for a pattern and get some steel laser cut, I have done this mock up on a 62 Buick Special diff. They used 13" rims and have 4.5" x4 [114.3x4] bolt pattern. My wood pattern takes Nissan Pulsar calipers and the Pulsar rotor is used. Job is currently shelved covered in dust until I can get to dealing with other shit on this orphan vehicle.
OZ-E-Rodders Rod and Kustom Club Member #31
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