Repairing striped rear axle threads

[rockfla]

Or if there is enough thread left, use a 9/16 NF Jam nut up against the Finished nut you use as a locker. If you can't find a 9/16 NF Jam nut I have plenty of them in stock.

[trainguy]

Originally Posted by JWL

I totally endorse your repair choice because I have followed the same procedure on several axles. NONE of which have since failed. If the axle taper is a reasonable fit within the hub there will never be a problem. If the taper is a poor fit, a 3/4" thread diameter won't save it.

Thanks for the vote of confidence.Refreshing in this world of nay-Sayers! Rather than leave the car set until I have the time to install another axle,after a lot of thought,I chose to repair the threads.with 50 years as a mech. Engr. and 40 years owning a machine shop,I felt I could trust my judgement.I kinda knew when I posted this project that it would be somewhat contiversal.And if it was a failure I would post the results to keep fellow Barners from making the same mistake.Phil

[Admiral]

Originally Posted by trainguy

Thanks for the vote of confidence.Refreshing in this world of nay-Sayers! Rather than leave the car set until I have the time to install another axle,after a lot of thought,I chose to repair the threads.with 50 years as a mech. Engr. and 40 years owning a machine shop,I felt I could trust my judgement.I kinda knew when I posted this project that it would be somewhat contiversal.And if it was a failure I would post the results to keep fellow Barners from making the same mistake.Phil

I hope the repair works flawlessly for you and is totally safe. Please keep us posted.

[ford38v8]

Originally Posted by trainguy

A loose nut usually causes a sheared key and or worn key way,not a broken axle.Phil

Phil, In answer to your request to explain, a loose nut certainly does cause those symptoms you cited, and more: As the keyway is not designed to take the twisting load, and the inside end of the keyway being the weak spot, probably 90 % of broken axles will have broken at that spot. Close examination of the inner end of the keyway for cracks before installation is strongly advised for any used axle. When the taper takes the load as designed, the keyway is not under stress and will not crack. If you are not able to fully torque the axle nut, the taper may not remain seated under all driving conditions, thereby setting up the failure of the axle.

[trike84]

as for hub retainer's I like the safety hub style. simple design and piece of mind knowing that if you do break an axle your not going to lose it.

[trainguy]

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Originally Posted by ford38v8

Phil, In answer to your request to explain, a loose nut certainly does cause those symptoms you cited, and more: As the keyway is not designed to take the twisting load, and the inside end of the keyway being the weak spot, probably 90 % of broken axles will have broken at that spot. Close examination of the inner end of the keyway for cracks before installation is strongly advised for any used axle. When the taper takes the load as designed, the keyway is not under stress and will not crack. If you are not able to fully torque the axle nut, the taper may not remain seated under all driving conditions, thereby setting up the failure of the axle.

Makes sense,I agree.I plan to torque the 9/16-18 thd to 125ft lbs.Should be enough to lock the taper.The taper on the axle is in very good condition as is the taper in the hub.Phil

[Zimmco]

Here's a photo of a crack from a loose axle nut. It was only a matter of time before this would have broken off completely.

[JSeery]

Originally Posted by trainguy

Makes sense,I agree.I plan to torque the 9/16-18 thd to 125ft lbs.Should be enough to lock the taper.The taper on the axle is in very good condition as is the taper in the hub.Phil

If specification is: "tighten nut 356074-S to 200 to 220 foot pounds; then continue tightening to the next castellation providing final resultant torque does not exceed 275 foot pounds."

125 ft-lbs sounds a little on the "light" side, why so little torque? A 9/16-18 should have a higher torque value than 135 ft-lbs, should be more in the 150 to 175 ft-lb range.

[trainguy]

Originally Posted by JSeery

If specification is: "tighten nut 356074-S to 200 to 220 foot pounds; then continue tightening to the next castellation providing final resultant torque does not exceed 275 foot pounds."

125 ft-lbs sounds a little on the "light" side, why so little torque? A 9/16-18 should have a higher torque value than 135 ft-lbs, should be more in the 150 to 175 ft-lb range.

Agree, your right 125 way to low try 165ft lbs.Thanks for the correction.Phil

[trainguy]

Originally Posted by Zimmco

Here's a photo of a crack from a loose axle nut. It was only a matter of time before this would have broken off completely.

Great picture,very interesting,looks like that axle was ready to break.Thanks Phil

[JWL]

Inadequate torque on the axle nut is easy to assign blame to. However, another, and equally responsible cause of axle cracks is the wear at the bearing journal and bearing. The axle is repeatedly cycled while operating off the centerline and as the brakes raise the weight of the car to center the shoes. The pictured crack does not appear to exhibit the wear one would expect to see if the hub was "working" on the key as a result of being loose.

[Zimmco]

I've added photos of the key to the original axle photo. It looks like the key was rocking back and forth under acceleration and braking. This was on the drivers side of a pickup I bought, and I was pulling the drum to check the brakes and bearings. I noticed that the nut came off too easily and the key looked bad, so I checked the axle closely and found the crack. The hub bearing and axle housing were OK and in are use now. I replaced the axle and installed NOS drums.

[ford38v8]

Originally Posted by JWL

...The pictured crack does not appear to exhibit the wear one would expect to see if the hub was "working" on the key as a result of being loose.

JWL, I have not seen that exact pattern of lateral crack either. I agree that that picture shows an unusual crack for a key working in the keyway. What I have seen has always been a crack from the end of the keyway in a generally linear direction up the shaft. Actual breakage of the axle may zig zag off in another direction, but would more likely start with a linear crack. I'm certainly no expert, but only know what i've seen.

[ford38v8]

Zimmco, I guess what that demonstrates is that metal fatigue will make its own decision on where it cracks!