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#1075646 11/16/22 03:40 PM
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Have a 87 Monte SS so it'll have the 7.625 rear end. So basically I lookin for clarification on what size posi unit to get. 26 spline I know, but I see a ton of 7.5 posi units 26 spline... to be clear, would the posi unit I look for would be the 7.625? Cause I see ones that state 7.5.... and 7.5/7.625....

Any help appreciated.


1987 Monte Carlo SS, Lightning Rod equipped, engineless/2004-R,Holley carb, edelbrock intake, hooker headers, moog,Iceman crossmember, umi suspension, eibach springs,so much more,no computer/emissions.
http://www.cardomain.com/ride/2167110
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I would be looking for the 7.5/7.625 or just the 7.625 . If there is one I was really interested in and it was only 7.5 I would just call the manufacturer and ask them if it works because from my previous research they all interchange except for the bolt in Powertrax lock right units, the tech support at powertrax said the unit was dimensionally different between the 7.625 and 7.5. Also assuming your car is stock make sure the differential is a 3 series or 3.23 or numerically higher as it has to do with ring gear thickness if I remember correctly.

Last edited by 88ssBrent; 11/17/22 11:41 AM.
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Not a rear end guy, so this may sound weird. But is there a difference between the two? Thought the size just deals with the ring...

And yeah, mines a series 3 (3.73).


1987 Monte Carlo SS, Lightning Rod equipped, engineless/2004-R,Holley carb, edelbrock intake, hooker headers, moog,Iceman crossmember, umi suspension, eibach springs,so much more,no computer/emissions.
http://www.cardomain.com/ride/2167110
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I just found this as it should answer all your question and I feel that it is a reputable source as it's coming from Strange engineering.

https://www.strangeengineering.net/product-category/ring-and-pinion-gears/gm-10-bolt-7-5/#:~:text=It%20featured%20a%207.5%20inch,interchangeable%20between%20the%20two%20axles.

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So if im reading that site right, I can use a 7.5 posi unit in my 7.625 rear end with all the parts already in my rear end.


1987 Monte Carlo SS, Lightning Rod equipped, engineless/2004-R,Holley carb, edelbrock intake, hooker headers, moog,Iceman crossmember, umi suspension, eibach springs,so much more,no computer/emissions.
http://www.cardomain.com/ride/2167110
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That's how I read it also.


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