Repairing striped rear axle threads

trainguy

trainguy

Well-known member
While reassembling the left brake drum during the Barners Bash at Vic Ps the axle nut on the left wheel would not come up to torque.We stopped tightening the nut and put the cotter pin in, and completed the tour.Now that I am home I was in the process of replacing all 4 wheel cylinders.Upon removing the axle nut I found that the axle thd was stripped.Rather than pull the axle I have decided that I will attempt to rethread the 5/8-18 thd. to 9/16-18.I locked the brake on the opposite wheel and started the engine in reverse raised the rpm of the engine and filed the bad thd till the shaft measured .562.The whole process took about 10 min.I have a 9/16-18 thd cutting die due in tomorow,and with a little care I will be able to rethread the axle.I don,t feel that the 5/8 to 9/16 change in size will make much difference in the strength of the axle.Phil
 
To give you an idea of the difference in Torque values, one set of values for a 5/8 grade 8 bolt is 230 ft-lbs, from the same source a 9/16 grade 8 bolt torque value is 169. That is a fairly large difference, a 26.5% decrease.
 
For such a beautiful car, I wouldn't cheapass. Get a new axle, it will ease you mind on every right-hand curve.
 
Not cheap just lazy.Yea retainers would be a good idea.I actually have a spare axle and plan to change it this summer when I have time just a band- aid till then. PHIL
 
Speaking of retainers ,any one have them fitted to hubs with mechanical brakes?
Lawrie
 
I would doubt that the axle is case hardened! Case hardening is normally used for wear applications not for torsional flexing.most likely it is made from a alloy such as 4130-4140 heat treated aprox. 48 RC.Phil
 
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Lawrie said:
Speaking of retainers ,any one have them fitted to hubs with mechanical brakes?
Lawrie
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Lawrie, I have often thought about the same thing. If you come up with a way to do this, let us know how you did it. Driving these 80+ y.o. cars all over Gods creation, we never know when an axle might snap, and we have a tire, wheel, drum and hub go flying past us :eek:
 
trainguy>>>While reassembling the left brake drum during the Barners Bash at Vic Ps the axle nut on the left wheel would not come up to torque. We stopped tightening the nut and put the cotter pin in, and completed the tour.>>>

I'd sorta like to know 3 things. Why was it disassembled in the first place? How much tork was applied while reassembling? And how do you suppose they got stripped? Thanks.

Jack E/NJ
 
It wast taken apart to fix a wheel cylinder that was not releasing,the threads started yielding at about 125 ft lbs. I have no idea how it got stripped.This was the 1st time I had the wheels off the car.Phil
 
trainguy>>>the threads started yielding at about 125 ft lbs.>>>

Thanks. What you're planning to do seems way better than the way it was. Carry on! 8^)

Jack E/NJ
 
The main function of the nut is to lock-up the taper thus taking the load off the key and to keep the hub on the axle.It really has little to do with the strength of the axle.A loose nut usually causes a sheared key and or worn key way,not a broken axle.Phil
 
trainguy said:
The main function of the nut is to lock-up the taper thus taking the load off the key and to keep the hub on the axle.It really has little to do with the strength of the axle.A loose nut usually causes a sheared key and or worn key way,not a broken axle.Phil
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A loose nut is usually the root cause of a broken axle.
 
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.
 
You could help mitigate the situation by ensuring the hub is a good "wringing" fit on the taper by lapping it in with grinding paste, as described on this forum many times in the past.

Mart.
 
Mart said:
You could help mitigate the situation by ensuring the hub is a good "wringing" fit on the taper by lapping it in with grinding paste, as described on this forum many times in the past.

Mart.
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Yes, I agree with you, Mart. If you're not going to tear the rear end apart to properly repair this issue at least get some valve-lapping compound and make sure the tapers match as well as possible. Heck, this is something we should all do to ensure a good fit between these critical surfaces. I did it with my car; it's cheap and only takes a couple minutes.
 
JM 35 Sedan said:
Lawrie, I have often thought about the same thing. If you come up with a way to do this, let us know how you did it. Driving these 80+ y.o. cars all over Gods creation, we never know when an axle might snap, and we have a tire, wheel, drum and hub go flying past us :eek:
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Not to hijack the thread but I am replacing an stripped axle in my 38 an plan to a retainer. Will probably have to drill 2 holes to mount it.
 
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