Thinking of keeping the 7.5 rear - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 18 Old 03-19-2009, 04:07 PM Thread Starter
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Thinking of keeping the 7.5 rear

Pickup on a few threads that the 7.5 rearend weighs 20-40# less then the 8.8. Debating on staying with the 7.5 since this is an SVO not a torquey v8. My concern is that I will not be able to run a MM PHB or TA. Have anyone installed these components onto the 7.5? I think the tube size differs from the 8.8?

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post #2 of 18 Old 03-19-2009, 04:32 PM
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I dont have the tube diameter measurment, but I would stick with what you got.
Its easier and cheaper (if necessary) to just modify to make it fit the 7.5" (IMOHO).






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post #3 of 18 Old 03-19-2009, 04:36 PM Thread Starter
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Thanks! I will measure the tube differences for the hell of it when I get home. I have an 8.8 on my other car.
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post #4 of 18 Old 03-19-2009, 05:06 PM
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I have a couple of spare U-bolts from my t-arm build and just measure one of 'em.

The tube diameter should be the same between the 7.5" and the 8.8" at 2.75".
The problem with the 7.5" is the little ears that the Griggs and MM use for the front struts of the t-arm. The aren't present on the 7.5" so you'll have to make up a U-shaped strap arrangement to keep the front of the diff from rotating. Not insurmountable but a PITA none the less.

Last edited by Moving Target; 03-19-2009 at 05:08 PM.
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post #5 of 18 Old 03-19-2009, 05:16 PM Thread Starter
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"little ears"? Can't picture those for some reason.
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post #6 of 18 Old 03-19-2009, 05:24 PM
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The 8.8" differential case used for the Mustang (top image drudis posted) shows two extensions on either side of and just behind where the pinion flange is located. They were used to mount a vibration damper (aka moose balls) and Griggs and MM use them for mounting the t-arm to the axle housing.

Like so:


The extensions/ears/things with the holes were not present on the 7.5" axle I deep-sixed.

Last edited by Moving Target; 03-19-2009 at 10:40 PM. Reason: clarifying the difference between the 7.5 and 8.8 damper mount
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post #7 of 18 Old 03-19-2009, 05:27 PM
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I can speak from experience that the 7.5 has slightly small axle tubes. We installed a Ghetto-Rigged PHB and used an axle mount that clamps around the tube on the driver side. The PHB originally came off of an 8.8 car and it would not fit our housing because it is a little smaller. The clamp part bottomed out and it was still super loose on the housing. I ended up taking some 3-inch exhaust tubing, splitting it down the center and weling it to the axle tubes, and then put the clamp on axle mount. It works fine now. The MM PHB uses a totally different style of axle mount so you should be fine, but yes, there are outside differences between the 8.8/7.5.
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post #8 of 18 Old 03-19-2009, 05:29 PM
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Silly engineering decision...whoever made it.

Good work-around though.
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post #9 of 18 Old 03-19-2009, 05:37 PM
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ehhh the car got 2nd out of 95 at a 24hrs of LeMons event. It's a real peice of #### though and I agree it shouldn't be fast or reliable, but it was/is. I kept waiting for it to let go and have horrific crash. It would have pretty awesome.
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post #10 of 18 Old 03-19-2009, 06:00 PM
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The 7.5's Ive seen had the mooseballs on them just like the 8.8 does and thus, the mounting ears.
Might depend on what the 7.5 originally came from ?

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post #11 of 18 Old 03-19-2009, 06:01 PM
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Quote:
Originally Posted by jw33 View Post
ehhh the car got 2nd out of 95 at a 24hrs of LeMons event. It's a real peice of #### though and I agree it shouldn't be fast or reliable, but it was/is. I kept waiting for it to let go and have horrific crash. It would have (sic) pretty awesome.
Uhm, my silly comment had to do with the axle tube diameter change between the 7.5" and 8.8" axle housings, not your working, work-around.

Nice finish.

Last edited by Moving Target; 03-19-2009 at 06:08 PM.
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post #12 of 18 Old 03-19-2009, 07:09 PM
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Can you get an LSD for the 7.5"? I've never looked for one...

What about gear selection?

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post #13 of 18 Old 03-19-2009, 07:31 PM Thread Starter
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Quote:
Originally Posted by gt40mkII View Post
Can you get an LSD for the 7.5"? I've never looked for one...

What about gear selection?
Same as 8.8.
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post #14 of 18 Old 03-19-2009, 07:58 PM Thread Starter
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Just looked at my 7.5. Mine has the counterweight, but it is attached differently then the 8.8. Doesn't use the front part of the housing as a mounting point.
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post #15 of 18 Old 03-19-2009, 11:45 PM
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The 7.5 hang the 'balls' on an adapter.
My aftermarket sway bar bracket fits the same on both axles.


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post #16 of 18 Old 03-20-2009, 02:16 AM
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Quote:
Originally Posted by gt40mkII View Post
Can you get an LSD for the 7.5"? I've never looked for one...

What about gear selection?
yeah they came in SVO, TC, 4x4 Rangers, Areostar, and Bronco II. The gear ratio selection is about the same and the 8.8. 4:10 and 3:73 are super common.
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post #17 of 18 Old 03-20-2009, 03:00 PM
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Originally Posted by jw33 View Post
yeah they came in SVO, TC, 4x4 Rangers, Areostar, and Bronco II. The gear ratio selection is about the same and the 8.8. 4:10 and 3:73 are super common.
Well you learn something every day. I thought all those got the 8.8.

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post #18 of 18 Old 03-20-2009, 04:49 PM Thread Starter
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Ford didn't start using the 8.8 in the mustang till 1986.
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