28 or 31 spline mini spool?

I am going to buy Richmond 3.80 gears, and Auburn mini spool, but have the choice between 28 and 31 spline spool. Which do I need.

 

if you are planning on keeping the stock axles, you will need the 28 spline.

 

Thanks, that is what I needed to know.

 

if you are going to race at the track. i know that nhra says if you are going to use a spool in the rear you have to use after market axles. if you do then the 31 is stronger.

 

I go to the track, but am not racing nhra style. Just test and tune. I figure by the time I am powerful enough to race, I will have broken an axle or two and will need to upgrade then, probably to something with rear disks. I am still in the 200-250 HP range, probably on the lower end of that. Thanks for the heads up.

 

i think companies like moser now make both 28 & 31 spline aftermarket axles.

 

I bought the Auburn mini spool in 28 spline. Pulled the axles and the differential, and verified...it IS 28 spline. Auburn also made the 31 spline.

 

all 8 inch ford axles are 28 spline, the 31 spline were only in 9 inchers