28 spline or 31 spline

[Niagara Dave]

Hello everyone. I just ordered my kit. Trying to put together driveline parts. I'm going to do a SBC with 700 r transmision. I'm going to build max 400 hp. I purchased a 91 mustang rear end with 410 gears. I have to change the axels to 5 bolt. Should I change to a 31 spline carrier?

[Gordon Levy]

Really don't need to but I would seriously consider changing to a 3:55 gear or near that.

[Niagara Dave]

May I ask why? I figured with the over drive on the 700 r I was ok.

[Gordon Levy]

The car is very light, you don't need a lot of gear to make it quick. You will find the car will be quicker with less gear because of it's light weight and 400hp will more it really well. Less gear will also be easier on all the parts and you will be happier with the overall package. Cruising on the highway at 70 at 2000 revs with a 3:55 will be a lot more comfortable that at 3000 revs with a 4:10.

[Niagara Dave]

Thanks!

[Plebeian]

Just an FYI, good aftermarket 28 spline axles are around 25% stronger than the stock ones.

[Niagara Dave]

Got the rear end stripped going out for sand blast and picked up 355 gears today for $50. Good day!

Thanks for the advice.

[erlihemi]

Watch the hub diameters on aftermarket axles. Some of the 28 spline 5 bolt "conversion" axles are retaining the small 4 bolt hub and you will need a spacer. I forget if this is 72 or 75mm so check your wheels and discs. Maybe its the drum brakes that are smaller.