31 or 28 spline, any way to verify without pulling an axle?

[reamer]

On a '73 9' rear (Open) I what to research a Limited Slip set-up, other that pulling an axle, is there a way to tell?
Thanks

 

[garberz]

Buy a 31 spline LS device of your choosing, then buy some new 31 spline axles if you don’t already have them. I wouldn’t spend the money or time on a 28 spline locker. There’s really no way to tell unless you have prior documentation, or just pull one.

Mark

 

[DirtDonk]

Agree with Mark wholeheartedly. But only if you really want a limited slip.
For starters though, no early Bronco ever came with 31 spline axles from the factory. So if you know for a fact that yours are original, then they're 28 spline for sure.
But the 31-spline swap has been a popular trick for over 40 years now, so if they've ever been changed or you don't know, then the only way to know is to pull them out and count.
But chances are good that if it's still open differential, they're more likely to be 28 than 31 still.

The reason for the extra money to upgrade is that limited-slips and especially lockers put much more stress on the axle shafts than do open diffs. Some companies like ARB and Detroit no longer even sell 28 spline lockers due to common breakage.
So instead of compromising strength to get some possible use out of an LS diff, the extra $250 or whatever it costs now, is better than going through the hassle of changing later and having to change the diff again too.

Now, I'm a big fan of also telling most people that they won't ever need a traction type differential. If they're not wheeling or don't live in the country, then don't bother. Most did not and they work just fine.
And snow & ice are not always valid concerns. They can be, but you have to look at the downsides carefully if you have not already.

Anyway, those are some more of the arguments for and against.
Do you know if yours are original or not?

Paul

 

[spap]

Nope no way to tell unless you pull it

 

[sprdv1]

Buy a 31 spline LS device of your choosing, then buy some new 31 spline axles if you don’t already have them. I wouldn’t spend the money or time on a 28 spline locker. There’s really no way to tell unless you have prior documentation, or just pull one.

Mark

totally agree....

 

[msmith]

Pull it out, count, put it back in. 45 minute job with refreshments.

 

[reamer]

I have to replace the Oriley's auto parts E-brake cables (too short) and I have no lift,
for new W.H. E-brake cables that should fit, So pulling an axle is a "while I'm I there" action.
But since this is probably a 28-spline, small bearing axle diff housing, Can I stuff a 31 spline axle in a small bearing housing?

 

[garberz]

.......Can I stuff a 31 spline axle in a small bearing housing?

Here ya go!

https://www.wildhorses4x4.com/product/Extreme_Duty_Rear_Axle_Set_6675yr_Sm_Bearing_10in_Drum/bronco_rear_axle

Mark