Machining a 4 lug to 5 lug diff

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Offline 65 Fastback

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Machining a 4 lug to 5 lug diff
« on: March 09, 2021, 04:43:52 pm »
Hi all,
I have 65 FB 6 cyl daily commute and want to change the rear from 4 lug to 5 lug to go with discs I’m putting on the front. I’m in no rush to swap the 6 for an 8 and 8in diffs seem hard to come by or too expensive. I saw an article on drilling the existing axels for 5 lugs (US) and wondered if anyone had bothered doing something and née a Melbourne based machine shop they would recommend or knew of a similar low cost swap.
Tony

Online AussiePhil

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Re: Machining a 4 lug to 5 lug diff
« Reply #1 on: March 09, 2021, 06:29:27 pm »
Hey Tony,
You can buy four lug to five lug adaptors at a reasonable price!
Just google it!
Cheers Phil.
If you've never buggered anything you've never done anything!
But if you've buggered a lot maybe you're not very good at it!

Offline GEOFF289

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Re: Machining a 4 lug to 5 lug diff
« Reply #2 on: March 09, 2021, 07:27:10 pm »
Hey Tony,
You can buy four lug to five lug adaptors at a reasonable price!
Just google it!
Cheers Phil.

Not sure those are legal here.

Online AussiePhil

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Re: Machining a 4 lug to 5 lug diff
« Reply #3 on: March 09, 2021, 07:50:24 pm »
Not sure those are legal here.
Yes, your most probably right Geoff.
May just have to get an old set of axles?

Hey Tony,
Try BigAl here on the forum, he may have something or at least know!
Cheers Phil
« Last Edit: March 09, 2021, 07:59:00 pm by AussiePhil »
If you've never buggered anything you've never done anything!
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Offline 65 Fastback

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Re: Machining a 4 lug to 5 lug diff
« Reply #4 on: March 10, 2021, 06:55:07 am »
Thanks guys.

I was checking widths of diffs from other cars and note the LC/LX Torana has the same width diff (BW) as the 65 Mustang.

Online AussiePhil

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Re: Machining a 4 lug to 5 lug diff
« Reply #5 on: March 10, 2021, 08:32:12 am »
Hey Tony,
You'd still have to do something about the axles, they have a different stud pattern!
Cheers Phil.

Added 10/3/21,

Also spring carrier width and probably universal different?
Agree with Dwyane and 67fb.

Cheers Phil.
« Last Edit: March 10, 2021, 01:06:50 pm by AussiePhil »
If you've never buggered anything you've never done anything!
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Offline GEOFF289

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Re: Machining a 4 lug to 5 lug diff
« Reply #6 on: March 10, 2021, 09:07:10 am »
Knowing what I'm talking about isn't always a pre requisite for me chiming in but wouldn't it be pretty routine for a diff shop to cut the four lugs off and weld some five lug ones on? Doesn't seem any more challenging than shortening axles or all manner of other things a competent diff shop does.

Online Dwayne

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Re: Machining a 4 lug to 5 lug diff
« Reply #7 on: March 10, 2021, 09:12:08 am »
Knowing what I'm talking about isn't always a pre requisite for me chiming in but wouldn't it be pretty routine for a diff shop to cut the four lugs off and weld some five lug ones on? Doesn't seem any more challenging than shortening axles or all manner of other things a competent diff shop does.

A diff shop can convert the axles over to 5-stud, but then you also need to swap out the drum brakes to 5-stud as well.

By the time you do all this, probably cheaper to just buy a used 65-66 v8 diff and just drop it in.

Offline 67FBGT

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Re: Machining a 4 lug to 5 lug diff
« Reply #8 on: March 10, 2021, 12:26:15 pm »
Quote
probably cheaper to just buy a used 65-66 v8 diff and just drop it in.

Exactly. Just buy the required second-hand components, recondition as required, and simply bolt them in. Same as Mustang owners converting their I6 cars to V8s have been doing for decades.

Online AussiePhil

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Re: Machining a 4 lug to 5 lug diff
« Reply #9 on: March 10, 2021, 01:15:45 pm »
Hey all,
As a matter of interest I got onto US Ebay and the amount of used Mustang four lug axles available is remarkable.
Cheers Phil.

Have a look at this on US Ebay,

"Mustang 4 to 5 lug rear wheel conversion"

He obviously has a jig and doesn't remove the axles!
That's how I'd do it also!

Can be done, but you decide if you'd be happy with it!

I'm a machinist and wouldn't do any worse!
Then again get into a fatality how do you stand!
Cheers Phil.
« Last Edit: March 10, 2021, 01:32:08 pm by AussiePhil »
If you've never buggered anything you've never done anything!
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Online AussiePhil

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Re: Machining a 4 lug to 5 lug diff
« Reply #10 on: March 20, 2021, 06:40:41 am »
Hey 65 Fastback,
birdman has an 8" Differential for sale, not sure if 4 or 5 stud?
In for sale by private sellers!
But in Eastern Creek.
Cheers Phil
If you've never buggered anything you've never done anything!
But if you've buggered a lot maybe you're not very good at it!