Broken Rear Axle Shaft

[Lawndart]

Well, that was fun. I was coming home last night around 9PM and slowly turning a corner after stopping at a rural crossroad when there was a bang and my Bronco was getting squirrely. We were squatted in the rear as I headed for the side of the road. I glanced in the rearview and saw my rear tire rolling into the ditch beside me. I did not make it to the road side. With my Bronco still in the road, I jumped out to see this –
(pic taken this AM)

A little stunned, I briefly assessed the situation. Crap. I locked the front hubs and engaged the front axel and powered my Bronco the side of the road. I had just gotten off the highway about 5 miles back where I was running at 65-70mph… I was less that a mile from home. A neighbor was sitting on their back porch and had heard and seen the excitement. They drove over and gave me a ride home. I called a tow truck company and they came right out and we got it back in my driveway.

Looks like it has been compromised for a while… scary!

What could have caused this? Wheel bearing failure?

Bronco history: I purchased this Bronco about a decade ago with 37000 miles and it was lifted. I drove it home from halfway across the country. I bought new suspension and returned it to OEM height. I replaced the wheel bearings and seals about 75000 miles ago. Now I have 124500 miles on my good ole Bronco!

Time for formulate a repair plan. A couple questions.
1) How difficult will it be to remove the broken shaft? I have never removed one that was broken in this fashion.
2) About replacement – should I replace both axle shafts or just the one?

 

[DirtDonk]

Can’t say with 100% certainty, but most likely a bum wheel bearing.
In all of my experiences, and listening to the stories here, it almost always happens during, or right after a long, high-speed freeway run, or another type of load, such as towing or hauling.
Usually happens with a few hundred pounds of camping gear, or a small trailer. But the most common is a freeway run.
Builds up heat to the point where the bearing freezes up and probably the axle is compromised anyway.

Looks like you have the small bearing rear end? Can’t say from here, that’s what it looks like.
Ran up against the hard mileage limit a little early. Usually we consider the end of life to be about 125,000 miles for the bearing. They’ve aged out by 100K, but are near failure at 125.
At 75, you ran up against it early. If it turns out to be the bearing that is. At 75,000 miles the bearings in my 71 were toast. But they were still working.

Also, do you have a limited-slip rear end? Or a locker? Those seem to compromise the axle shafts more quickly.

You can certainly get away with replacing just the bad axle, but you can’t ignore the other one.
At least check it out, check its condition and make sure the bearing is smooth and quiet and still has lots of grease. You don’t want it too easy, but you certainly don’t want it rough and tight. That just builds up more heat.
Whether you replace one axle or both, certainly replace the other sides bearing at least.

 

[Lawndart]

Thanks DirtDonk!

Yes, I believe it is a small wheel bearing and my drums are 10" (measures about 10.5" ID of the drum).
I have the 3.50 ratio limited slip rear.

I will follow your advise and change both bearings, so likely both axles (looks like this one was cracked for quite some time).
Heading back to the scene and see if I can gather some of the brake parts.

 

[Yeller]

looks like you were lucky, which this was a super rare occurrence, happens way more than has been publicized. Although I'm confident that most are not going to see this, it does happen, been a year or so since I've seen one. On the upside, it is really nice to see a bronco out and about that doesn't have ancient tires on it, Date coded the 37th week of 2023.

 

[bigmuddy]

On an axle tube that old, make sure to inspect the race as well.

I would offer you one of my spare axles but they are all large bearing.

 

[DirtDonk]

Mine too. And they’re already living under someone else’s bronco anyway!

I don’t think we’ve ever kept a tally here, but I’d say it happens more often on the small bearing than the big bearing, but it happens to both.
I was lucky and while I was doing the rear brakes on mine, I noticed that the bearing sounded a little dry when I moved the axle.
Since I didn’t know anything about them, I decided to change them. Boy, what a difference!
Apparently they were going out for awhile because in places where I could just sit at the traffic light with my feet off the pedals, after the bearings I had to keep my foot on the brake pedal, or the bronco would just roll.
Big difference. I bet I was building up a lot of heat in that area on those old tire bearings!

Speaking of which… Maybe we should make a regular part of our maintenance, checking the axle end temperature after a freeway blast.
If anyone has an older vehicle with higher mileage and unknown bearing age, this might be a diagnostic tool once we get some data points to compare to.

 

[Lawndart]

On an axle tube that old, make sure to inspect the race as well.

I would offer you one of my spare axles but they are all large bearing.

Appreciate that!

 

[Lawndart]

The non-broken shaft came out easily. The bearing is toast. I have not noticed any bearing noise.
https://flic.kr/p/2q33LwT
I confirmed 28 splines. The drum measures about 10 3/8 inches ID and about 2 1/2 inches depth wise on the brake surface.
I measured the outside diameter of the bearing.

I was not able to get the other axle out, but I have not tried too hard. I want to get the axles ordered and while I am waiting, I will work on getting it out.
Broken shaft bearing looks plenty lubed.

I believe I will go with Wild Horses - they have the shafts with studs, bearing and retainer already installed.
So, do I have 10 inch brakes & small bearing?

 

[bigmuddy]

How about a pic of the end of your axle tube for reference.

 

[DirtDonk]

So, do I have 10 inch brakes & small bearing?

Yes to both.
Small bearing is just under 3 inches and big bearing is just over 3 inches.

 

[Timmy390]

Maybe it's just the angle of the bearing in the cup but it sure looks oblonged to me. It's tight at the top and loose at the bottom. Like it's been spinning in the cup and damaged it. I suspect bearing failure in its past which damaged the axle and over time it let go.

While my axle didn't fail the cup was oblonged and was leaking. I had to change the cups. Was a total PITA but came out well.

I upgraded to HD 31 spline axle shafts and set 20 bearings. Expensive but fixed the issue.

Tim

 

[Timmy390]

Also glad your OK. I had a wheel come off long ago (not Bronco) and it was scary. Very scary.....

Tim

 

[Lawndart]

How about a pic of the end of your axle tube for reference.

 

[Lawndart]

Maybe it's just the angle of the bearing in the cup but it sure looks oblonged to me. It's tight at the top and loose at the bottom. Like it's been spinning in the cup and damaged it. I suspect bearing failure in its past which damaged the axle and over time it let go.

While my axle didn't fail the cup was oblonged and was leaking. I had to change the cups. Was a total PITA but came out well.

I upgraded to HD 31 spline axle shafts and set 20 bearings. Expensive but fixed the issue.

Tim

I just took another look - I think it is a combo of the angle, the backing plate getting a little beat up and loose after I took off the bearing/axle retaining nuts. Thank you for the heads up and I will certainly inspect once I get the axle shaft out.

Thoughts on getting the broken one out?? I had some long PCV pipe and ran it from the other side, but that cross pin is very difficult to get by. I sanded down the handle on a long/thin'ish screwdriver to fit into the PCV to try and get around the pin, but that isn't going to work. Thinking about welding a nut and using a slide hammer.

Off to order the shafts.

 

[Timmy390]

Thinking about welding a nut and using a slide hammer.

That would be my attack plan.

Tim

 

[Lawndart]

Sidebar - I did find most of my missing brake parts

 

[DirtDonk]

Congrats, things are looking up already!

 

[Apogee]

Weld a nut and/or tap the shaft...should be pretty soft in the center to drill and tap. Either way, a slide hammer is going to be your friend IMHO.

 

[Lawndart]

Round one - Earlier this week, I was able to drill about 3/4" deep at the center of the shaft with a 1/4" bit. As I started to step up on my way to just under 3/8" (size of my slide hammer shaft), I ran into some dull bits. Then I tried welding a couple nut to the shaft.

My welder was too wimpy and I did not get enough (or any) and the nut came off while I was sliding. Crap.

I ordered a couple bits from McMaster and a good tap.
Round two - Yesterday, I drilled and tapped for my hammer. The hammer was too wimpy and the threads on the slide hammer gave out. Crap.

Round three - This AM, I headed to Harbour Freight for a bigger (5lb) slide hammer (I did not know where else to go). I was able to step up from 3/8" to 7/16" with my drill bits and tap for 7/16-24. Slide-tap, slide-tap, slide-tap and the axle was free! uuuu-rah!

 

[Tiko433]

Glad you and the Bronco not hurt. Good job on getting it out