28 Spline Vs 31 Spline

[f8tlfiveo]

I broke a stock axle on 260 rwhp with nitto drag radials on a 4 k launch with a well prepped track. Not really a launch though. The car didn't move, snapped the axle off in the carrier and twisted the splines. Pain in the ass to get out. Had to pull the other axle and diff to get the stub out. Upgrade now, don't wait.

 

[srtthis]

As far as I know, you can use the differential but the axles won't work fom Ford trucks except the Ranger. I think the 03-04's Cobra had 31 spline trak lock's. Here's a chart for reference. pages 51-52

http://www.differentials.com/Catalog_2012/index.html

Bottom line is you can swap the carrier and then buy new axles.

01 cobra
03/04 cobra (carbon clutch)
05+ GT's (carbon clutch)
07+ GT500's
the 97+ F150's (might be older ones also)

thats just off the top of my head

 

[cleanLX]

The reason people break the stock axles at near stock hp levels is because they set the car up to dead hook (with an associated bog) and something has to give.
If you are going to the track on sticky tires and afraid to launch at high rpm to induce some tire spin, then get 31splines.
If on the other hand you are willing to launch hard enough with a higher psi on those same sticky tires and work your way backwards thru the day to an optimal launch rpm and tire pressure hook/spin deal than the 28's will do you well.
I likely had over 300 passes on the stock 28splines launching between 5000-6250rpm with between 9.5-15psi in the tires. The wide spread in rpm and psi is due to track conditions. Once the car was dialed in the rears would roll over a couple feet than scratch hard for about 10-15 feet then hook... 1.69's-1.70's with 232hp in a 3200lb car.

If you are unwilling to put the time into seat time, learning to read the track and learning to read your car, then by all means overbuild to avoid the likely hood of track breakage.

I will not be dedicating that kind of commitment to my new combo, so I went with 31's and a Detroit.

 

[RangerJoe]

Mine came from a 5.0 explorer. Not sure if the V6's have them or not.

Joe

 

[25thmustang]

The reason people break the stock axles at near stock hp levels is because they set the car up to dead hook (with an associated bog) and something has to give.
If you are going to the track on sticky tires and afraid to launch at high rpm to induce some tire spin, then get 31splines.
If on the other hand you are willing to launch hard enough with a higher psi on those same sticky tires and work your way backwards thru the day to an optimal launch rpm and tire pressure hook/spin deal than the 28's will do you well.
I likely had over 300 passes on the stock 28splines launching between 5000-6250rpm with between 9.5-15psi in the tires. The wide spread in rpm and psi is due to track conditions. Once the car was dialed in the rears would roll over a couple feet than scratch hard for about 10-15 feet then hook... 1.69's-1.70's with 232hp in a 3200lb car.

If you are unwilling to put the time into seat time, learning to read the track and learning to read your car, then by all means overbuild to avoid the likely hood of track breakage.

I will not be dedicating that kind of commitment to my new combo, so I went with 31's and a Detroit.

This is very true. 5500-6250 and your bound to spin over a dead hook and possible broken parts.

My 140k mile stockers last many mid 12s with 1.69-1.71 60's and never broke. The Ranger axle broke on pass #4 with Hoosiers. I equated it to the fact that one ranger axle spun one direction for many miles and I installed it going the other way. Fatigue of reversing the torque applied to it (if that makes sense to anyone).

FYI I think I paid $40 for my 31 spline carrier and either $100 or $150 for 31 spline fox length 5 lug axles.

All in all it's a crap shoot. You may or may not break an axle. Same with a T5, hit or miss.

 

[revhead347]

Messing up the launch is usually the best way to break an axle. Every one messes one up every once in awhile though. I've messed up a few in my time.

Kurt

 

[NIKwoaC]

I feel like these arguments are kind of like the stock block arguments. You can try to explain away why some live longer than others, but at the end of the day you're asking a component to go far above and beyond what the engineers ever intended it to, and some of them are just plain gonna break.