85 gt 7.5 or 8.8 rear end

[stogie]

I read that the 85 and older came with the 7.5 and the 86 and newer came with the 8.8 rear end. Below in the picture is where I read it. I'm looking to get either 3.73 or 4.10 gears for my 85 gt so I went and checked mine out and to me it looks like a 8.8 so I would like to get your guys second opinion since it's my first mustang not really sure.

 

[anthonydalrymple]

It does look like someone already swapped in an 8.8. What does the tag on the diff say? With the rear up in the air; roll a tire forward. Does the other tire roll forward too? Mark the tire & driveshaft; rotate the tire one full revolution while counting how many times the driveshaft turns to figure out the gear ratio you already have...

 

[stogie]

It does look like someone already swapped in an 8.8. What does the tag on the diff say? With the rear up in the air; roll a tire forward. Does the other tire roll forward too? Mark the tire & driveshaft; rotate the tire one full revolution while counting how many times the driveshaft turns to figure out the gear ratio you already have...

Nice thanks I'll check it out when I get a chance . how do I how many times would the drive shaft spin for a 3.73 or 4.10 just to know or how do I figure out the ratio sorry I'm New to all this it's my first muscle car and real project car. I always had a Honda before this.

 

[Blown347]

One full turn of the wheel will show you the ratio by the drive shaft turns. Ex: 1 turn of the wheel turns the drive shaft 3 3/4 turns then it has 3.73s

 

[stogie]

One full turn of the wheel will show you the ratio by the drive shaft turns. Ex: 1 turn of the wheel turns the drive shaft 3 3/4 turns then it has 3.73s

Right on thank you