smacked1

so how do i determine which one i have on my mustang? and is it just the axles that are 28/31 spline?

edit: so i was just reading and the tranny out and driveshaft are also 28/31 spline, so how do i tell/determine which one i am using

Tony71502

Splines are essentially the "gear teeth" in that mechanical connection. The more splines means more teeth. The axles have a certain number of splines on the end of them, where they connect to the differential in the middle of the rear end housing. Therefore, the differential has to have the same number of splines as the axles in order to make the mechanical connection.

Mustangs come stock with 28 spline axles and differential. If you did have 31 spline axles and differential it is because someone converted it from 28 splines. More splines basically means higher capacity before the mechanical connection fails, as in the splines are sheared off.

The driveshaft connects to the rear end by a flange and 4 bolts. The driveshaft slips into the transmission tailhousing and connects using splines, similar to the axles and differential. The transmission output shaft and driveshaft yoke have the same number of splines, but the spline count on these parts has nothing to do with the axles and differential.

Chances are you have a 28 spline differential and axles if your car is mostly stock. If you need to find out, you would have to pull an axle out of the rear end housing. If you wanted to see how many splines are on the driveshaft you would again have to remove it from the car.

OnyxCobra

some mustangs come with 31 spline, if you have a '91 though stock would be 28.

mjr46

stock is 28 also the carrier into which the axles slide has the correct teeth to accept 28 spline...31 are not interchangable with 28 units.

smacked1

Ok thanks for the info, the car has a new motor, tranny, and rebuilt the rear end so its not close to stock but im not sure about the axles

The reason im wondering is because i want to do the 5 lug conversion and i was going to buy the kid off latemodelresto but i see they have 28 and 31 spline kits

Im not sure if its still stock since the guy i bought the car from had the rearend rebuilt and put in 3.55's and redid the rear drums and a aluminum driveshaft

So not sure what to do and what to look for to see what i have

projectresto83

Pull out an axle and count the splines on it. Simple as that

smacked1

I have 28 spline! Thanks everyone for the info, im going to do the 5 lug conversion it's ok just to stay with 28 spline right? Big difference in how much power they can handle vs. 31 spline?