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Author Topic: Need clarification on early 6.75" to late 8" rear end swap.  (Read 1558 times)

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Offline 65ShelbyClone

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Need clarification on early 6.75" to late 8" rear end swap.
« on: November 21, 2014, 09:03:37 PM »
My exhaustive searches have been turning up conflicting information.

I have a 1977 Mustang II 8in rear with ovate holes in the leaf spring perches. My car is a '72 with smaller round holes. Some accounts say that it's a direct swap and others say that the MII isolator brackets etc. are needed for an early car like mine.

Which is it?

Barring a simple answer, does anyone have pictures of the differences in hardware and perches? I can machine adapter/alignment plates if necessary; I would just like to do it without having to tear the car apart first.
'72 Runabout - 2.3T, T5, MegaSquirt-II, 8", 5-lugs, big brakes.
'68 Mustang - Built roller 302, Toploader, 9", etc.

Offline dick1172762

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Re: Need clarification on early 6.75" to late 8" rear end swap.
« Reply #1 on: November 21, 2014, 10:41:05 PM »
Early Pintos had a small hole about 1/2" in dia. Then from 74 or 75 the 6 3/4" and the 8" from Mustangs  II went to an oval cutout in the spring pad. This was done so better soft pads would fit and remove vibration coming from the rear end. There is a couple of ways to get around this problem. You can make a plug out of 3/8" aluminum, the same shape as the oval cut out. Put a 1/2" hole in the center and your done. Put the plug on top of the spring, lower the rear end over it and your done.  Aluminum plug can't come out because the rear end is on one side and the spring is on the other side.  Other way is to weld an oval shape plug into the spring pad.  It will also need the small hole in the center. It's really easy to fix and VERY necessary to keep the rear end centered with the car. I've done it both way and they work the same. The weld way works the best if your going to use lowering blocks.
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Offline 65ShelbyClone

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Re: Need clarification on early 6.75" to late 8" rear end swap.
« Reply #2 on: November 22, 2014, 04:58:57 PM »
I had envisioned something like this before posting the thread. Kind of like a really thin lowering block.

'72 Runabout - 2.3T, T5, MegaSquirt-II, 8", 5-lugs, big brakes.
'68 Mustang - Built roller 302, Toploader, 9", etc.

Offline dick1172762

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Re: Need clarification on early 6.75" to late 8" rear end swap.
« Reply #3 on: November 22, 2014, 05:34:17 PM »
That should work really good. Good work.
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Offline 65ShelbyClone

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Re: Need clarification on early 6.75" to late 8" rear end swap.
« Reply #4 on: November 22, 2014, 08:51:54 PM »
That's good news. Thanks for the help.  :D
'72 Runabout - 2.3T, T5, MegaSquirt-II, 8", 5-lugs, big brakes.
'68 Mustang - Built roller 302, Toploader, 9", etc.

Offline dick1172762

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Re: Need clarification on early 6.75" to late 8" rear end swap.
« Reply #5 on: November 22, 2014, 10:32:21 PM »
Another thing I've done is if your using  a 1" lowering block and if the bolt that goes thru the spring has a head say a 1/2" tall, I will place a dowel pin the same dia as the spring bolt head and just long enough to stick above the lowering block about 1/4" and fit into the spring pad.  I tried using a 1" longer bolt thru the spring and lowering block but they kept breaking, so I tried the dowel pin and that fixed it.
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