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My questions about the differential of my 66 has disappeared with the forum format changeover (or most likely I cannot navigate it properly to find it). So...I believe that someone replied back to me that if my rear end has two dimples (no rear end jokes hear!!) it is a 9" differential. What say y'all?

Refresher: 66 with swapped in 302 and C4. Originally a 289 w/3 speed. Does not look like the differential has been replaced. Axle code is 6.
 

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Yeah 2 small round dimples is an 8 and a big semi-circular bulge at the back is a 9. If axle is original, you have an 8 inch with 2.80:1 ratio, very common, very streetable, very durable.
 
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Discussion Starter #6
Yeah 2 small round dimples is an 8 and a big semi-circular bulge at the back is a 9. If axle is original, you have an 8 inch with 2.80:1 ratio, very common, very streetable, very durable.

Ok...so I finally got under there and found the tag and according to it I have a 7.75 in diff. But it also has the dimples AND I can get a deep socket on the bottom nut. Confusion sets in.

Year​
Tag Code​
Type​
Ring Gear Diameter​
Ratio :1​
Ring Teeth​
Pinion Teeth​
1966​
WCZ-E​
Conventional​
7.75​
2.8​
42​
15​

756544
756545
 

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Never mind that stuff,just roll under the car and if you can put a deep socket on the bottom nut you have an 8 inch,you can`t put a socket on a 9 inch.
What he said 8inch. Buy a limited slip and gear and build it! It will roll well.
Yeah 2 small round dimples is an 8 and a big semi-circular bulge at the back is a 9. If axle is original, you have an 8 inch with 2.80:1 ratio, very common, very streetable, very durable.
And what HE said!
 

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Discussion Starter #8
What he said 8inch. Buy a limited slip and gear and build it! It will roll well.

And what HE said!
Every tag decoder website says I have a 7.75" diameter ring gear and not an 8". I copied and posted one site in the previous post...here is a different site saying the same thing.
WCZ-ECougar '67
Falcon '64-65
Mustang '65-67
2.80​
7 3/4 in​
NL​
28​
I know I have a couple brain cells left but I'm still confusewd as to what I have. If I in fact have a 7.75 can I change internals and keep the housing? Can I go to an 8" ring gear? I know the diff needs some work (has quite the whine we rolling down the road) so when I go to rebuild it what are my options?
The car will be a weekend driver.
 

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You have what is known as an 8" rear end. The ring gear for the different ratios varies slightly in diameter. Obviously the 2.80 ratio ring gear is "only" 7.75" in diameter.
 

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You have what is known as an 8" rear end. The ring gear for the different ratios varies slightly in diameter. Obviously the 2.80 ratio ring gear is "only" 7.75" in diameter.
Yes The charts I'm seeing seem to show some ratios in 7.75 on the 8 inch. It may be the carrier differs on these like a spicer. There are way fewer resources on this diff, but all rebuild and upgrade parts are available if you dig.
 

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You have what is known as an 8" rear end. The ring gear for the different ratios varies slightly in diameter. Obviously the 2.80 ratio ring gear is "only" 7.75" in diameter.
You have what is known as an 8" rear end. The ring gear for the different ratios varies slightly in diameter. Obviously the 2.80 ratio ring gear is "only" 7.75" in diameter.
So when I go to find the parts for a rebuild I look for parts that will go in an 8" diff???
 

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Yes The charts I'm seeing seem to show some ratios in 7.75 on the 8 inch. It may be the carrier differs on these like a spicer. There are way fewer resources on this diff, but all rebuild and upgrade parts are available if you dig.
Nope. The carriers are the same. The difference is solely in the diameter of the ring gear to accommodate the size of the pinion. Some are 7-3/4, most are 8 inches. Even more confusing is that you'll find the same ratio with both sizes of ring gears, depending on the tooth count. LOL. The same applies with the 9-inch rear as well.... you'll find 8-3/4 inch and 9 inch ring gear diameters. You'll also find a 9-3/8 inch ring gear on some Lincolns and trucks but these require a bit of clearancing of the housing.
 

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My questions about the differential of my 66 has disappeared with the forum format changeover (or most likely I cannot navigate it properly to find it). So...I believe that someone replied back to me that if my rear end has two dimples (no rear end jokes hear!!) it is a 9" differential. What say y'all?

Refresher: 66 with swapped in 302 and C4. Originally a 289 w/3 speed. Does not look like the differential has been replaced. Axle code is 6.
Stangnan,

I pulled the 8” 2.80:1 carrier out of our 66 to swap in a Currie built Los with 3.55:1 gears.
stockcarrier was working fine just wanted Los and taller gears.
you are welcome to our stock unit if you wish,
we Are in so cal so shipping cost could be an issue,
let me know.

Pat
 

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756775

Give him a call, just rebuilt my rearend and was confused on what type of rearend I had because it was actually a 67 rearend I’m in my 68 he will answers all your questions.
 
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