1966 Rear Axle, 28 Spline or 31 Spline?

[Swerve]

Hello...

I have an early, Oct '65 build date, Bronco.

The rear axle tag decodes as 4:11 LS, but no reference to spline count.

Assuming that the rear axle is stock, how can I tell if it is 28 spline or 31 spline without tearing it apart?

Were both spline options even available at that time?

Thanks, Swerve...

 

[71Broncitis]

It's 28. No Early Broncos came with 31.

Sent from my XT1254 using Tapatalk

 

[Swerve]

Less than 60 seconds and I have my answer!

Thanks!

 

[sanndmann3]

and that was 6:00 in the morning...
this is a really high quality website.

 

[brianstrange]

Also, the hub side of the axle may look like a 31 spline, but it's not.

 

[ared77]

I've always been able to tell a 31 spline on Mustangs, Torinos, etc by the solid end with the two holes as opposed to the oval that's in the end of a 28 spline axle. That isn't true if looking at Bronco axles?

I'm just trying to learn here.

Thanks!

Norm

 

[brianstrange]

I've always been able to tell a 31 spline on Mustangs, Torinos, etc by the solid end with the two holes as opposed to the oval that's in the end of a 28 spline axle. That isn't true if looking at Bronco axles?

I'm just trying to learn here.

Thanks!

Norm

That's correct. Some had the two holes, but were still 28 spline

 

[66Bronco]

The housing should have a drain plug on the back side. All 28-spline and my '66 Roadster came with a factory Posi.


-Terry

 

[Skiddy]

The housing should have a drain plug on the back side. All 28-spline and my '66 Roadster came with a factory Posi.


-Terry

I haven't seen any ford 9" factor drain's?:?

 

[thegreatjustino]

The housing should have a drain plug on the back side. All 28-spline and my '66 Roadster came with a factory Posi.


-Terry

The '66 would have had a fill plug on the back, not a drain plug.

 

[H20rider]

I have a ‘68 half-cab. Is there an easy way to determine the rear spline count? Easy as in, not opening it up to count.

 

[Broncobowsher]

I have a ‘68 half-cab. Is there an easy way to determine the rear spline count? Easy as in, not opening it up to count.

No.

We can tell you it was built with 28 spline, that is guaranteed. But what has happened in the past 50+ years cannot be answered. 31-spline has been a common upgrade for 30+ years.

The good news is you don't have to take it all apart. Just pull a tire and brake drum off. Go 4 more nuts on the axle retainer. You may need to use the brake drum as an improvised slide hammer. That is all you need to get an axle out. With one side higher on a jackstand you shouldn't even loose any gear oil. Count the splines, put it back together and order up a new set of 31 spline axles to go with whatever differential upgrade you are planning.

 

[sprdv1]

Less than 60 seconds and I have my answer!

Thanks!

LOL, right

 

[sprdv1]

No.

We can tell you it was built with 28 spline, that is guaranteed. But what has happened in the past 50+ years cannot be answered. 31-spline has been a common upgrade for 30+ years.

the man w/the plan As you see wealth of knowledge here

 

[H20rider]

No.

We can tell you it was built with 28 spline, that is guaranteed. But what has happened in the past 50+ years cannot be answered. 31-spline has been a common upgrade for 30+ years.

The good news is you don't have to take it all apart. Just pull a tire and brake drum off. Go 4 more nuts on the axle retainer. You may need to use the brake drum as an improvised slide hammer. That is all you need to get an axle out. With one side higher on a jackstand you shouldn't even loose any gear oil. Count the splines, put it back together and order up a new set of 31 spline axles to go with whatever differential upgrade you are planning.

Great information. Thanks….I will follow it!