I have found a guy who has a couple 9" rear ends that fit into my mustang but the question is which gearing should i get? Ive never changed my rear end so idk what would work best so any advice would be appreciated. He has a 2.75, 3.00, and a 3.70.

 

I have 3.70 gears in my '67 convertible. The acceleration is great, but on the highway I'm spinning 3000 RPM at 65 mph. I'm not digging that at all.

Of those three choices, and based on the fact I'm not trying to build a race car, I'd personally go with the 3.00 gears.

Of course I'm not taking my own advice - instead of replacing the differential, I'm going to install an AOD in my Mustang.

 

We need much more information in order to help you select the right gear. What engine? What mods? What chassis? What transmission? What use for the car?

 

need more info.
what engine, what gearbox, what tyre size (225/60R15 etc) do you have in the back?
what do you prefer?
great accelleration and high revs at 60mph (bad fuel economy, annoying) or
bad accelleration and low revs at 60mph (good fuel economy)

 

Ok i have a stock 390 with a c6 transmission right now. I dont know the exact tire size but the are around my 14s so they arent big. Im going to be driving it a lot so i would like to have decent gas mileage.

 

I would choose the 3.00. With the FE, the 2.75 might even be okay. I would definitely stay away from the 3.70 for your application.

 

I agree. I think 3.00 would be good especially with out overdrive. The 390 makes plenty of torque so it does not need low gears.

 

ok thanks that helps alot. after everything gets put together ill try and post pics.

 

agree. would use the 3.0:1 as well with that.

 

Ok so the guy wants $350 for the rear end and $75 for a driveshaft. Do you guys think that is a good deal?