I have a 1990 5.0 mustang automatic I wanted to change the rear end so i purchased
22501 - Auburn Pro Series Limit Slip Differential - 31 Spline 8.8in (86-12 V8; 11-12 V6)

1 24001G87 - Ford Racing 3.73 Gears (86-93 GT)

1 73000 - Moser 8.8 Axles w/ Studs - 31 Spline 5 Lug (79-93 5.0L)

1 50240 - Ford Racing Differential Cover - 8.8in
1 50275 - Ford Racing Ring & Pinion Installation Kit - 8.8in Solid Rear (86-04 V8)

1 24011 - Ford Racing Aluminum Driveshaft - 31 Spline (96-04 GT, Mach 1; 96-98 Cobra )

my question is i have a 31 spline diff and 31 spline axles and i had purchased the 31 spline drive shaft as well but american muscle tells me that it will not fit my automatic transmission and i cant seem to find anything that fits my set up. would i be able to use the drive shaft that i purchased or my old one and if not where could i get a new drive shaft that would fit my set up. thanks guys.

 

You can use the driveshaft but, you will need a 28 spline yoke to use it. You can probably use the one off the old driveshaft.

The driveshaft is connected to the rear-end with a u-joint. Same goes for the slip yoke. If the old driveshaft and the new take the same u-joint, then have the yokes switched out.

 

31 spline driveshaft has no relationship to 31 spline axles/differential. There are no splines on the flange that connects the drive shaft to the rear end, only four bolts. Return the driveshaft and get an aluminum driveshaft meant for your year car.

 

Thanks a lot guys I figured I could use one that would fit my car I just couldn't seem to figure it out and wasn't sure. Thanks a lot guys you guys were very help full, ill give you guys an update on how it turns out.