Ford 9” axle shaft snapped

[CopperBronco]

So my axle snapped at the hub today… . Luckily going 5mph… nobody was hurt, on quiet country road. Had my kid and nephew with me, luckily in car seats and shoulder belts, and LATCH system, the works!

Two questions… anyone hypothesize why a 9” rear would crack at hub? See photos, it had rust in it, probably cracked before I even bought it last year. My Dad is a gear head and was with me, said it was probably from original casting problem.

Second, I need new rear axle, probably replace front while I’m at it. Any recommendations for a 66 Bronco daily driver with a Dana 30 up front? Disc brakes? 2.5” lift?

 

[raleigh_bronco]

Yukon Chro-Mo

 

[Speedrdr]

Things like that will cause a high pucker factor for certain!

Randy

 

[DirtDonk]

could easily have been an original defect, or likely as not a failed wheel bearing, or a little bit of PO abuse. Maybe a few too many jumps into the Wally World parking lot?
Either way, axle shafts are easy for the Bronco. Where are you located? Shipping might decide, but you'll need to know a few more things about what you have before you buy.

Can you remove the old inner piece and verify that it's still a 28-spline factory piece? If so, that and knowing whether or not you have a small or big bearing will get you what you need. Along with what year, but in your case the '66 through '75's were the same as others in most categories on the "need to know" list.
Just for reference, here's our Rear 9" Axle page from the website: https://www.wildhorses4x4.com/category/bronco_rear_axle
You'd be looking at the "heavy duty" versions rather than the "Extreme" versions, which are 31-spline and need a change of differential parts to work with. Unless it turns out that's already what you have. Doubt it, but that's why you have to check before ordering.

So from us at least, it's about $350 for the two shafts (but you can buy just one if you choose) and a few bucks for new seals. Shipping too of course...
You don't have to replace the other one, but it would not be a bad idea at this point unless you're able to determine that it was in fact an original defect. If it was abuse though, then both axles got the same amount.

Good luck. Glad everyone was safe. Even if slightly annoyed!

Paul

 

[CopperBronco]

Thanks Paul! Was reading that exact webpage tonight… no idea on spline yet…. Drums are 11”, but can you tell me from where to where to measure depth? From inside drum housing I got right around 2 1/8”, or 2 3/16” depth, but write up said 2 1/4”…. And photos on Wildhorses site are small and fuzzy. My photos look more like #2, but measurements suggest 76-77” large bearing… just need to pull drum cover and measure the bearing I guess? Is there a place I should look for cast number on rear end? Maybe not from a Bronco, but F150? I have a 78 continental 302 technically(made in Bronco MI factory), and had a poor man’s F150 lift… Always a chance this was a scrap yard rear end… where it snapped was impossible to notice without pulling the axle, and I just had an alignment and it drove amazing… no shimmy, etc… so no signs there either. Just a freak accident… probably will prioritize replacing all of them at this rate! Definitely never want to see that again, was going quite fast only a few minutes before, could’ve been bad.

 

[CopperBronco]

Also any good videos online or instructions on axle shaft install? Want to do it right, as a newbie everything is a first, but so far everything I’ve done myself hasn’t broken yet

 

[B RON CO]

Hi, unfortunately you had a rear axle shaft break. You replace the shaft, not the whole axle. You can also inspect the front axles, and pack the bearings unless you did this already. I inspect the front hubs and pack the bearings every brake job. But you don't replace the whole axle. The guys who drive hard on the trails do this job a few times a year. The rear axle shafts pull out and the hub flange is used to attach a slide hammer. Since yours broke off maybe you need to weld something on to attach a slide hammer. Luckily this doesn't happen very often. And you are right, you would not find the problem until it happens. Good luck

 

[CopperBronco]

Hi, unfortunately you had a rear axle shaft break. You replace the shaft, not the whole axle. You can also inspect the front axles, and pack the bearings unless you did this already. I inspect the front hubs and pack the bearings every brake job. But you don't replace the whole axle. The guys who drive hard on the trails do this job a few times a year. The rear axle shafts pull out and the hub flange is used to attach a slide hammer. Since yours broke off maybe you need to weld something on to attach a slide hammer. Luckily this doesn't happen very often. And you are right, you would not find the problem until it happens. Good luck

Thanks! And correct, the axle shaft broke, not the rear end itself… I was wondering about removal… have to remove drum and I’ll only have a small stub to grab onto… I’m assuming it takes some force to remove?

 

[CopperBronco]

Also does the axle shaft diameter (the tube size), change with small bearing vs. large bearing? Curious if I can diagnose this based on break area… Wildhorses gives bearing size outer diameter which I haven’t torn apart yet. Assuming inner diameter varies a little as well.

 

[Yeller]

Thanks! And correct, the axle shaft broke, not the rear end itself… I was wondering about removal… have to remove drum and I’ll only have a small stub to grab onto… I’m assuming it takes some force to remove?

Yes it does take some force, except for those that don't LOL. the center of the axle is soft and can drilled and tapped or if you have a welder you can weld something to the end to get it pulled out.

 

[Timmy390]

I've found it's generally the bearing that's holding things in the housing. Overall snug/tight fit and sometimes RUST.......The exception for me has been if the splines are twisted and then it's a real bear.

As mentioned you may have to drill and tap the center of the axle and then use a slide hammer.

Tim

 

[gnpenning]

This video while not exactly what you are asking about it does cover what you need to know. Skip through as needed.

 

[Broncobowsher]

Don't have a good view of the break. But what I see, looks like it has been cracked in half for a long time and you got some rust propagation about half way across. You had been running on half an axle shaft for a long time. It does sometimes happen. Mass produced parts, long service life, loads in excess of original engineering (tire size, gearing, power, etc.) Add in unknown history. If you want it to cost 10x as much, you could go all aerospace and have tracability of raw materials and go for frequent rebuilds and inspections. Back when TWA existed, I got a tour of there overhaul facility. They had X-ray machines that were massive to look through metal parts. When the testing costs more than the part costs to make.

You need a new axle. Surprisingly not even going to recommend going all crazy on a high end axle. The standard level of axles work incredibly well. The standard modern replacment axles today I think are better than the originals. The machine work is generally a higher level, the material quality control is better as well. This is in general for most everything produced.

 

[DirtDonk]

Agree with what the others have said. You do not need to replace the front axle shafts because a rear broke.
You don’t even know how often it’s been in four-wheel-drive or if there’s even any wear and tear on them at all.
The U-joints do wear out of course, but that’s an inexpensive fix. If an axle shaft breaks up front nothing happens to the wheel.
It’s what’s called a full-floating setup just like they have on big trucks in the back. Our rear axles are semi floating while the heavy duty adjustable tapered roller bearing types are full floating.
So the front isn’t in any danger of the wheel falling off unless you have not maintained the front bearings as was mentioned.
And that happens a lot so if you have not serviced the front wheel bearings you should do so because you don’t know if the PO did.
Ever!

 

[DirtDonk]

You can measure the rear wheel bearing with the brake backing plate still in place.
Since you can remove an axle and bearing while the brake backing plate is still attached to the housing, the housing opening is pretty close to your bearing size.
So if you have over a 3 inch diameter hole there, it’s a big bearing.

I would say from your measurements you have 11 x 2“ brakes. Standard stuff for an early model. I believe the actual measurement is taken at the shoe friction material so don’t worry about the depth of the drum unless you’re comparing to another drum.
Just measure the shoe width .

 

[DirtDonk]

There’s also a seal you will need behind the bearing.
So don’t forget that.

With any luck you can pry the bearing out easily. Although if your luck is bad the bearing will come right out because the housing is a little buggered.
But I don’t suspect that at this point. You might be able to thread a couple of screws into the bearing center and wobble it out by hand. More often that they’re not however they’re pretty stuck with age and you’ve already said there’s rust in there.
So those slide hammer comments of earlier could come true.
But as said, you can either drill and tap the center and thread in a bolt and pull all that, or weld a boat to the center and pull on it.

 

[.94 OR]

But as said, you can either drill and tap the center and thread in a bolt and pull all that, or weld a boat to the center and pull on it.

The bigger the boat the better.

 

[DirtDonk]

And your dingy is bigger than his whole bolt!

Paul

 

[CopperBronco]

Thanks guys! Got it pulled apart, it is a big bearing 66-75 9” rear, with 28 spline, and the bearing is 3”, and yes, 11”x2” drum. Ripped apart very quickly, slid right out no problem. Always shocking to me how little holds together a Bronco.

 

[CopperBronco]

New axle shafts ordered and should arrive tomorrow, now I need to get a boat to pull out my other shaft.