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7.5 Rear end question?

  • Thread starter Thread starter Thebigwhopp
  • Start date Start date Dec 5, 2018
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Thebigwhopp

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#1
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I would like to keep my 7.5 rear end in my car and not convert to an 8.8 rear end what is the cheapest way to make it posi. I would also like to add 373 gears or 355 gears, approximately pushing 300HP with new build what gears should I go with?
 

General karthief

wonder how much it would cost to ship you a pair
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#2
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Why? The cost to build a 7.5 would be the same and have half the strength as an 8.8
 
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Thebigwhopp

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General karthief said:
Why? The cost to build a 7.5 would be the same and have half the strength as an 8.8
Click to expand...
I would have to swap the front over to 5 lug and in the 85 that would be expensive unless I ran 4 lug in front and 5 lug in back.
 
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Thebigwhopp

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General karthief said:
Why? The cost to build a 7.5 would be the same and have half the strength as an 8.8
Click to expand...
If you have any suggestions or advice on cheaper build i'm all ears. Keep in mind I have an 85
 

General karthief

wonder how much it would cost to ship you a pair
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There are many 8.8 traction lock rears with 4lug axles
 
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Thebigwhopp

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General karthief said:
There are many 8.8 traction lock rears with 4lug axles
Click to expand...
Do you know of any off the top your head so I can look for them?
 

BlakeusMaximus

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Any 86 and up 5.0 equipped mustang right?
 
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Thebigwhopp

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BlakeusMaximus said:
Any 86 and up 5.0 equipped mustang right?
Click to expand...
I thought those weren't posi?
 

90sickfox

Wasn't a pretty sight...and I've got big hands
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All the mustang 5.0s from 86 to 93 have limited slip posi traction 4 lug 8.8 rears. The clutch packs aren't hard to rebuild. They wear out causing a bunch of cats to one wheel peel.
 

General karthief

wonder how much it would cost to ship you a pair
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#10
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An old school method of helping the clutch packs last is to change the oil every 40-50 thousand miles and then drive in a tight figure eight slowly for 5 or 6 rounds, kinda cleans the clutch faces.
 
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FoxChasis

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Also, 7.5 in 1982 through 1985 Capris and Mustang are already Traction-Lok from the factory (they are not "posi" so please stop calling it that) so there is no need to "convert" to T-L. And 3.55 is a 8.8" gear. It is not available for 7.5. The close equivalent for a 7.5 is 3.45.
 
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General karthief

wonder how much it would cost to ship you a pair
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Ford-traction lok
Gm-positrac
Dodge-sure grip
 
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90sickfox

Wasn't a pretty sight...and I've got big hands
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General karthief said:
Ford-traction lok
Gm-positrac
Dodge-sure grip
Click to expand...

Thought " sure grip " was the stuff that held dentures ...
 

General karthief

wonder how much it would cost to ship you a pair
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#14
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Poly grip was also used in some rambler applications
 

02 281 GT

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#15
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All this proves is that GM came up with the catchiest name for its proprietary limited slip differential.
 

7991LXnSHO

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#16
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When the 8.8 was new in Mustangs and available in the Ford Performance catalog, I found it a lot less expensive to put the Eaton style (clutch plate) actual Ford Limited slip in the stock 7.5” rear end.
Now, a salvage 8.8” rear is easier to find that should bolt in. I’d start with a good 8.8” core and go through it with new bearings, seals, and possibly clutches.
 
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Rcdgl

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#17
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You can buy 7.5 in traction locks in Ranger trucks and early foxes and aftermarket. I have a 2.73 stock one in my 79 and a Ford Racing one with a 4.10 gears in my 82. And there are four and five lug axles for them. My 4.10 has been 7.90 in the eighth with 1.80 sixty foots. So far so good. Its a lot lighter than an 8.8. No worries, I have several 8.8s waiting in the wings.
 

CarMichael Angelo

my rearend will smell so minty fresh,
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#18
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What?.
FoxChasis said:
Also, 7.5 in 1982 through 1985 Capris and Mustang are already Traction-Lok from the factory (they are not "posi" so please stop calling it that) so there is no need to "convert" to T-L. And 3.55 is a 8.8" gear. It is not available for 7.5. The close equivalent for a 7.5 is 3.45.
Click to expand...

What??? I’m not the one that has a problem with people using GM terminology for their Ford parts??

Say it ain’t so.
 

7991LXnSHO

wanna catch the space herp
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#19
  • Dec 9, 2018
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All of the Fox 5.0 Mustangs (except the 93 Cobra and maybe the turbo coupe super edition I am blanking out on) came with 8.8 rear ends and a LSD WITH 4 lug axles. Your wheels will not have to be changed, nor the front end parts. A wiki search will tell you for sure, but it seems like 85 was the first year the GT got the 8.8”.

General karthief said:
There are many 8.8 traction lock rears with 4lug axles
Click to expand...
 
Last edited: Dec 11, 2018
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7991LXnSHO

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#20
  • Dec 9, 2018
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Rcdgl said:
You can buy 7.5 in traction locks in Ranger trucks and early foxes and aftermarket. I have a 2.73 stock one in my 79 and a Ford Racing one with a 4.10 gears in my 82. And there are four and five lug axles for them. My 4.10 has been 7.90 in the eighth with 1.80 sixty foots. So far so good. Its a lot lighter than an 8.8. No worries, I have several 8.8s waiting in the wings.
Click to expand...
@Rcdgl any idea on HP and torque without me using a drag calculator? How many passes, how much other driving and what transmission are you using with the 7.5”?
I wish my Ranger had come with a LSD rear end.
 
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