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Will a 2.83:1 Standard Differential on 1967 Mustang work with a v8 engine?, those are the specs on the rear axle on my 67 Mustang and I was wondering if I could swap out my inline 6 for a 289 , preferably 302 without having to change rear ends

 

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Yes, it will work. However, your 6 cylinder has the weak 7.25" rear end. If you put a V8 in and "stomp on it" the rear end won't last long. There are many people who drive modestly with a V8 and the 7.25" lasts a long time.

Ok thanks but when I bought the car it already had a 5 lug nut conversion kit and it has writing on the axle that says 8 inch 2:83 what does that mean?

 

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You should post some pics of this differential. 2.83 is a 7-1/4” ratio. An 8” would be 2.80 or 2.79. Someone may have wrangled some 5-lug axles onto a 6-cylinder rear end. As stated, a 6-cylinder rear will not last long behind a V8.

MrFreeze

 

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It means that someone wrote it on the axle. If they were honest and knew what they were talking about it might be true, and means that you don't have the six-cylinder axle. Have you compared your axel with images of the 8" and 7-1/4" axles in your shop manual?

No but I’ll do that now , thanks

 

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You can use an 8 inch rear end for a V8. 2.83 ratio is considered good for economy and bad for racing. You can read more here; https://www.cjponyparts.com/resources/mustang-rear-gear-ratios-overview

I won’t be racing, I just want a little more power, like a 302

 

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Are the bolts for the rear end center section on the front or back of the rear end? If on the back you have the 7 3/4" , 6 cyl rear end. If converted to 5 lug, there is a good chance they did that by putting an 8" in there. 8"are ample for a street driven small block.

There on the front facing the steering wheel

 

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There’s pic up

 

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Are the bolts for the rear end center section on the front or back of the rear end? If on the back you have the 7 3/4" , 6 cyl rear end. If converted to 5 lug, there is a good chance they did that by putting an 8" in there. 8"are ample for a street driven small block.

There on the front facing the steering wheel

 

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That's an 8 inch.

So it will work with a V8 engine ?

 

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Yes, that is the standard rear end for small block v8s.

Ok thanks , so a 302 or a 351 Windsor should work just fine , one more question how could you tell it ws 8 inch by looking at it?

 

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Mine originally came with a 351w 2v and a 2.79 rear axle ratio with the FMX auto. With some 80s 4v intake on it and that 2.79 rear gear it still felt great and “fast” for the 90s as a high schooler BUT the 3.89 rear gear and the 5 speed it has now really livened it up!

That being said the 351w torque curve was probably a little better at making up for the 2.79 gear ratio than a 289 will be. You could always try it as is but if it were me I’d go to a steeper ratio. In my younger age I just threw a lower ratio at it that was lower than my friend had in his Camaro which actually was a little too steep until I swapped the cam later. Look up “starting line ratio” and step through that calc and then marry that with cruising speed/rpm you want and decide from there.

What is the difference between a 2:79 and a 2:83 rear ?

 

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351s came with the bigger 9 inch rear end. The first year of 351W was 1969. The 9 inch rear end cars also came with bigger front and rear brakes. Do you know what kind of brakes are on the front of your car? Do the front wheels have 4 or 5 lug nuts?

It been converted from 4 lug to 5 lug and there’s also disc brakes on the front

 

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Its time to start ripping out those old worn out parts and start installing some new stuff... Good Luck!

Your 100% correct!