Why did my axle break?

ursus said:
I have some axle shafts that are in nice shape except for an annular groove worn into the shaft where it rides in the seal inside the housing. Is this a potential site for breakage or not a concern (aside from oil leagake)?
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It appears this is the area of the breakage in my case. Groove gets worn and perhaps even a bit more heat at that one spot over 90 years. Maybe this spot becomes the "stress riser"?

ronn said:
maybe the HS buddies were doing hole shots, while you were out picking up lunch...........?
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I'm more worried about the transmission when they drive than the rear end. Crunch crunch crunch.

Hey, if it only breaks every 90 years, I'm good with it.
 
I had one crack and was lucky someone following me tooted and told me my right rear wheel was wobbling. Shure enough when I took it apart there was TWO cracks and would not have lasted long. I took the oppurtunity to take everything off up the the engine while I had it apart. After lots of $'s and 6 months of putzing it is back together and running fine. I got two used axles from Bert's and am VERY satisfied with everything I have got from Steve. He also knows just about everything you ever need to know about the A's and gives great advice!!! Jim
 
I had a job a while back where the failure mode was the gear end of an original axle shaft sheared where the gear attached to the shaft. There were actually two failure modes. Years before the differential had been overhauled by someone who did not understand carrier pre-load. When the car was back on the road the rear was locked. Henry's 40 horses broke it loose. Usually it does so by spinning the carrier bearings on the mounting hubs. In this case it was locked so tight that it sheared the hub on the ring side of the carrier. The car operated like this for about 8 years before the heat cycling finally got to the axle shaft and the left axle shaft sheared right at the gear next to the sheared carrier hub.

See the attached link for photos.

Tom Endy



http://www.santaanitaas.org/wp-content/uploads/2018/05/Differential-failure-2018.pdf
 
If I want to check the torque on those axle nuts, do I need to remove the wheel or can I just remove the hub cap? May be a stupid question, but I'm having trouble visualizing it.
 
Tom Endy said:
I had a job a while back where the failure mode was the gear end of an original axle shaft sheared where the gear attached to the shaft. There were actually two failure modes. Years before the differential had been overhauled by someone who did not understand carrier pre-load. When the car was back on the road the rear was locked. Henry's 40 horses broke it loose. Usually it does so by spinning the carrier bearings on the mounting hubs. In this case it was locked so tight that it sheared the hub on the ring side of the carrier. The car operated like this for about 8 years before the heat cycling finally got to the axle shaft and the left axle shaft sheared right at the gear next to the sheared carrier hub.

See the attached link for photos.

Tom Endy

http://www.santaanitaas.org/wp-content/uploads/2018/05/Differential-failure-2018.pdf
Click to expand...




Tom, perhaps you can get a hold of one the new one piece axles Steve from Berts mentioned and let us know what you think.
 
If I want to check the torque on those axle nuts, do I need to remove the wheel or can I just remove the hub cap? May be a stupid question, but I'm having trouble visualizing it.

Alexi_ There is a cotter pin to remove in order to check axle nut torque. It will be much easier to remove the wheel in order to get the cotter pin out and back in later. If there is no cotter pin in your axle, by all means install new cotter pins.
 
alexiskai said:
If I want to check the torque on those axle nuts, do I need to remove the wheel or can I just remove the hub cap? May be a stupid question, but I'm having trouble visualizing it.
Click to expand...



I would just remove the hub cap . Removal of the hub cap may require the removal of the wheel to bend back tabs


If you have an extra wheel and tire without a hub cap ,

maybe you could temporarily use it and save having to remove the hub cap on your nice painted wheel .

After the axle nut is retorqued the original wheel can be replaced

The 28-29 hubcaps can sometimes be snapped off like a modern hubcap
 
100 ft-lbs torque on the axle nut is extreme in my opinion as it increase the tensile stress in the axle shaft. Cracks occur in tension stress fields. I run with 50 ft-lbs, and have not had any issues doing so in over 50 years of Model A'ing.
 
According to my bolt chart, Grade 5 5/8-18 is good for 170ft-lb dry. Assuming the axle shaft is not quite grade 5 and with 90 years of use and fatigue I definitely wouldn't want to go over 100ft-lb. Last time I did mine I went to 90 and then lined up for the cotter pin.
 
ursus said:
I have some axle shafts that are in nice shape except for an annular groove worn into the shaft where it rides in the seal inside the housing. Is this a potential site for breakage or not a concern (aside from oil leagake)?
Click to expand...
Unless that groove was deep and had sharp edges I wouldn't think it will be a problem.
I think worn wheel bearings and axle tube could allow more flex and could be a contributing cause to broken axles.
I'm an easy driver, and have never broken an axle.
Hole shots, and spinning the wheel on mud or ice can certainly snap an axle.
 
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