Axle Woes

Wise men:

I am baffled. And worried. I need to understand how and why I have broken two (2) axle shafts in the span of about 35 miles of city driving.

I have a '46 CJ2A. My father bought it in 1969 and pretty quickly swapped in a Dauntless V6, T18 transmission and Warn overdrive. There is a little more of this Jeep's history in an "Early CJ" post about a mysterious clutch problem (solved, thanks to y'all), but it's crawled, bounced and/or dragged itself over half the dirt roads and rock piles in Northeastern California, without significant breakdowns. I think my older brother broke a passenger-side axle shaft in the mid-'70s, but that was drag racing, and I'm not really sure it wasn't the other guy (who had a V8 that supposedly could pop little wheelies) who broke the axle.

The Jeep was driven only rarely in the last 25 or 30 years. I got it this spring, and I've enjoyed working on it, reliving the good old days and driving the flat pavement of Southeastern Virginia. Until, one day, I broke the rear, driver's side axle shaft. On a 25-mph road, shifting from 2nd to 3rd, as best as I can recall.

I was, of course, dumbfounded. My best theory was that the axle shaft had developed a twist or a bunch of hairline cracks during some long-ago rock crawling, but had somehow hung together until it fell apart. According to this theory, I hadn't done anything wrong, I just happened to be in the driver's seat when the steel finally gave up.

It took me a loooong time to replace the axle shaft. I was learning as I went, and I needed borrowed tools, helpful neighbors, time with the manual and lots of online research before we got everything apart and the broken end out of the differential, installed a new axle shaft and buttoned everything back up. Eight days later, the new axle shaft was broken, in the same place (at the end of the splines) and in the same location on Earth (same part of the same street on the way to my mom's house. Weird.)

Some fun facts that may or may not help with the diagnosis:
-- This time, I starting from a stop. In 2nd gear, as usual. I'd say I was making a "spirited" start, but not trying to burn rubber or anything. I absolutely did not redline it and pop the clutch.
-- We'd had to remove the carrier from the differential to get to the broken piece (This is a Dana 41 rear axle, not the full-floating kind.). Scary as that was, it came out and went back in without much trouble.
-- The first replacement axle shaft I got was too fat at the tapered end. I could not get the hub all the way on. The diameter at the very end measured .018 inches wider than the original. I eventually had to give up and get another shaft.
-- The second replacement shaft was the opposite -- thinner at the tapered end. I wish we had measured it, too (I still can, but the neighbor with the tool is out of town), but the difference was significant. The hub went on very easily. Even the bearings went on easily. Probably too easily.
-- As a result of this smaller-diameter taper, the hub ended up seating slightly farther along the axle shaft, compared to the original. As a result, the brake drum rubbed the backing plate, ever so slightly, sometimes. -- I had a heck of a time getting the freeplay right, but after much subtracting and adding of shims, I do believe I got there.
-- This transmission allows you can put the Jeep in in low-range 2WD. Dunno if that could be a factor. Maybe that's a little too much torque in one place? But that's no way to drive around town, and I certainly wasn't in low-range at the time of either break.

So:
-- What the heck? You break axle shafts by drag racing or pinching your wheels between rocks, on a steep hill, putting it in granny gear, revving the engine and being mean to the clutch right? Not tooling around town, right?
-- Could I have done something during reassembly that contributed to the second break? What? If I shimmed improperly, the damage would be to the bearings, not to the axle shaft, right?
-- I'm ordering my third new axle shaft. Ugh! I guess I'll pay more and get New Old Stock this time, on the theory that it will be more likely to be within tolerances (I understand that "within tolerance" is a range, that both "Fatty" and "Skinny" may actually be within tolerances, and that my hub hole my have a smaller-than-usual diameter, still "within tolerance," but making a bad match with "Fatty."
-- Surely I don't have to drive my Jeep, a vehicle world-famous for toughness, in constant fear of snapping axles in two?

Any wisdom to offer? Thanks in advance.

 

Was this a "new" shaft as in an Omix-ada made in China replacement or an original take out?

 

Daryl: I don't have the sticker anymore, but I believe that yes, the second break was of an Omix-ADA axle shaft. It certainly was not a junkyard find. I ordered it from one of the usual online sources for old Jeep parts. I ordered the first replacement shaft (the one I didn't use because the taper was too fat) from a different usual online source. I have no particular gripe with these suppliers, I just thought that ordering the second one from a second source would ensure I was getting a piece from a different "batch." Same reason I guess I'll now order a New Old Stock.
Is there a known problem with replacement axle shafts?

 

Omix-ADA is NOT a well respected source for hard parts in many people's opinion. They're okay for shifter knobs and stuff like that I guess. But I. personally, won't buy anything from them that is mechanical in nature like gears, bearings, etc. Especially if safety is a concern like steering parts. That's my opinion based on my own experience and what I have read and seen of other peoples experiences ( I've heard plenty ).

You may find a good used shaft by putting an ad in the WTB section of our classifieds forum. If not, I would hold out for NOS from some other source.

And beware, some retailers sell the Omix stuff without disclosing the manufacturer in their ad or catalog. If there is any question, call the supplier directly and ask who made the part or where they got it from. Unfortunately, Omix is about the only supplier of many of the reproduction parts out there. So, used or NOS may be the only other option for many things. Worth the wait vs buying junk for more money, IMO.

You may consider replacing the entire rear axle assembly with a later model unit as well. The later Dana 44, either tapered or flanged will bolt in. Just have to make sure the axle ratios are the same.

 

Wheelie:

Thanks, I had no idea. So you think it's possible that my first break was from decades of use and the second break was from a bad part?

 

I fully expect the first axle shaft had decades of abuse while the second shaft was junk.
You definately should buy an original used axle assembly or used axle shaft.

Any axle assembly 1946 through 1962 will have 5.38 FDR and can fill your need.
Axle assembly from 1946 through 1950 is a Dana model 41.
After that was Dana model 44. (more FDR's available)

If you get a used shaft only they are all the same meaning "ten spline" from 1046 to late 1956.
Late 1956 to 1970 went to stronger (larger diameter) 19 involute splines.

 

What others have said! Omix has some pretty loose "specs" on just about all their replacement stuff, be it axles, pitman arms, or shifter boots. Some of those parts can get you dead. I don't buy any of their stuff anymore. Best bet is to find a used replacement or NOS but the latter isn't likely going to be easy to find. And I would absolutely not replace it with another D41 if replacing the whole unit. Not if you want to change gear ratios someplace down the road.

No doubt Daryl has one of those 10 spline axles sitting on the shelf.

 

I try to keep several spares on the shelf. Let me know if you need one. I wouldn't use a Omix or Crown axle as a fencepost.

 

Thanks, everyone. Blaming the part is usually a sure sign that's my own damn fault. But maybe not this time. I guess (I hope!)

 

While reading this thread, I immediately thought "Omix" when you were talking about the new axle going on the taper too far. I've seen this before. They are junk as far as fit, and sounds like in material too. I never got past the install on a friend's 3B, and ended up with a used original.
Find a used original axle shaft and you'll probably get another 30 years of abuse out of it.
-Donny

 

Key5a: Thaniks, that adds to the evidence.

 

Should be a Dana emblem on any factory shaft if I recall.

 

There is 'a guy' on the local CL that has piles of old axle shafts. If Daryl doesn't have one for you, search the Chico CL for Jeep Paksenta or something. Never dealt with him, just see his stuff from time to time.

 

Here is an interested article on the early Dana 25, 27 and 44.
Low Range 2WD on CJ3B.info

 

Danefraz and Dauntlless1971: Thanks! You guys are from my part of the world. I've only been to Bend a couple of times, but it is similar terrain to my hometown. I have been up and down Highway 32 to Chico a hundred times! My CJ2A is a Susanville Jeep, sadly ripped from the steep trails and go-fast dirt roads and plunked down in Tidewater, Virginia.

 

As I disassembled my axle -- again -- I thought about how it would be great if I got the Jeep going again by Saturday night (as in last night), because we had a guest arriving today, a college student from Turkey (long story). What's more American than a Jeep ride, right?
Well, the axle shaft I bought from Daryl arrived in yesterday's mail. Amazing. And I had everything buttoned up and was driving around the neighborhood by afternoon. So thanks again, everyone, especially Daryl.
Another thing: I was so much faster and confident at the taking apart and putting back together this time. What took days the first time took hours this time. Not that I was really fast or really confident, but compared to the first go-around, no comparison. I'll post a photo later.