Rear axle shaft thread broken

[DRG-ler]

Hi guys, a quick question.



The thread of my left rear axle shaft is in very poor condition. It definitely needs to be fixed. Can I get the axle shaft pulled out WITHOUT disassembling the differential?

If so, I'd have material welded on, turned over on the lathe, and cut a new thread. If the shaft cannot be easily removed, I will probably cut the next smaller thread in the assembled state and use a smaller nut.


Friendly greetings from Germany

Andy

[nkaminar]

Andy, can the thread be restored using a thread chasing nut? I had to do that to my car.

[DRG-ler]

Sorry, but Google Translation can't do much with "thread chasing nut". Nothing useful comes out of it. What do you mean exactly?

[Tom Endy]

The two axles, the carrier and the ring gear can be removed from the car as an assembly without pulling the rear end out of the car.

By removing the left axle housing the assembly can be pulled out. It is not as easy as described. You have to put the rear of the fame on jack stands and remove the brake drum and axle key from the right side, and deal with the radius rod on the left side.

Once the assembly is out of the car the defective axle can be removed by separating the ring gear carrier halves.

it has been done a number of times in hotel parking lots when a Model A suffered a broken axle on a tour.

Tom Endy

[Jim M]

Andy, You can NOT get the axle out with out a lot of disassembly. I had a cracked axle on my 29 Roadster. I took the rear end completely off then took drive shaft off while rear end apart, then too transmission all apart while the drive shar was off, then took the clutch out while transmission was out and then replaced pressure plate, gears, U-joint, differential gears, axles, had spring leaves sand blasted, new brakes, DONE! took me about 3 months to complete but soooo glad I did. Had a great time and learned an awful lot. Was lucky I belong to a club that the members are knowledgeable AND willing to help. Good luck and it is a lot of fun. These are great cars.

[jayvee34]

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If you have or can get a die of the same size and threads per inch, thread it onto your axle
using cutting oil as you thread it on, back it off, get a new nut of the same size, and that should take care of it, that is if the threads on the axle are not to badly wiped out.
Hope this helps.
John

[DRG-ler]

Hi Jim, Hi Tom ...



@ Jim, you are writing from 3 months ago. I don't have that time. My Ford is often booked as a prop for the film at the moment. I can't afford to be out of work for a long time. At the moment I'm going so far that I don't consider the problem with the axle thread to be world-shaking. After I bought the car with this problem (out of ignorance) I drove 2500Km, and that with up to 55 miles. The nut still holds, the entire thread still bears, but it no longer holds the required tightening torque for the cone fit. Therefore, the first priority for me is the repair. A restoration of all parts is currently out of the question for me. Especially since the rest of the car is in good condition, with the exception of a few brake parts that are currently being replaced.



If I have understood Tom correctly, the correct repair can be done with less effort than your way. This will be my solution in case the repair with a new smaller thread doesn't work. At first I only see this as an emergency repair until I have more time to repair everything correctly.



I can't expect much support from automobile / classic car clubs here. On the other hand, the car is too exotic, even if it was built here by ourselves. Mostly younger cars are driven in the clubs. Self-help is the order of the day.



Greetings Andy

[DRG-ler]

Here is a picture of the extent of the disaster ...







Greetings Andy

[jayvee34]

After seeing the picture above, re-thread it as I mentioned, and anew nut and you should be good to go.

[GRutter]

Relatively easy fix.
Watch this video. This works. Hardened nuts available from vendors.

https://www.youtube.com/watch?v=lC_z...5bcpNJQdDfO5H8

[nkaminar]

Andy: Thread repair nut or die:

[nkaminar]

You can make your own using a grade 8 nut (high strength) by grinding a slot in one flat.

[Synchro909]

Being in Germany, you have the option of reducing the size of the thread to the next possible metric size. GRutter's clip shows how they go to the next imperial size but you have more options. The original thread is 5/8 inch which is very close to 16 mm. It may be worthwhile considering a metric option. 14 mm may be an option.

[GRutter]

One of the benefits of staying with the imperial size is that the number of threads per inch is exactly the same. You are only removing enough material from the damaged axle threads to be able to run the die, and you won't be cross-threading the original threads.

[Synchro909]

Originally Posted by GRutter

One of the benefits of staying with the imperial size is that the number of threads per inch is exactly the same. You are only removing enough material from the damaged axle threads to be able to run the die, and you won't be cross-threading the original threads.

Good point. I didn't realise they were the same pitch.

[DRG-ler]

Soooo, new day, new luck ...

@ GRutter Just like in the video, I had imagined it. It should be a repair that works first.

Thread repair nut or die: Thanks for the tip. But thread cutting dies in (for us) US special threads are also available here in the shop. That is not the problem. The problem is with the nuts. You can also buy nuts in UNF here, but not hardened / high-strength ones!

Like GRutter, I already had the idea of ​​simply cutting over the existing thread with 9/16 "-18 and using a smaller nut. But you don't get this hardened here, or at least not as tight as you want as Syncro said, switch to a metric thread. Maybe I'll be lucky enough to get a long hardened castle nut with a longer thread.

I've even bought a die for metric M15x1.5 threads. Also a special size here in Germany. However, I did it without thinking. The core hole diameter of 5/8 "-18 is 14.5mm ... not 15mm. Half a millimeter is missing. So it will probably be M14 after all.

Greetings Andy

[nkaminar]

Here is what I would do: First try cleaning up the threads with a repair die or standard die. If that does not work go to 9/16-18. To solve the nut issue, buy a metric nut 10.9 grade which is smaller than needed then tap 5/8-18 or 9/16-18. Use a flat washer and lock washer rather than the cotter key.

Fastenal has a good internet article on threads, see https://www.fastenal.com/en/78/screw-thread-design. They say to use a nut of a higher grade than the threads. Also of interest is that the first thread takes 34% of the load, the next 23%, the next 16% and so on with diminishing share of the load as the threads are further from the washer or load surface.


The Fastenal article may be available in German.

[JoeCB]

My opinion, the grade of the nut is not that important if the length of thread engagement is significantly longer than about five or six threads. As stated in the previous post the load per thread diminishes rapidly as you move back from the engagement face. Just use a long nut, ensuring lots of thread engagement.

Joe B

[DRG-ler]

In advance I will go a completely different way. The tip came from a neighbor who drives an old Adler convertible from 1936. He gave me the tip to first cut the original thread so that it is clean again. Then the thread cutting die is cut and made tighter. With this tighter setting, the thread on the axle is recut again and again until the thread turns look clean again.

With this setting of the die, a thread mandrel is cut, which then has the same thread as the one on the axis. And this threaded mandrel is used as a gauge to turn a completely new nut made of hexagonal steel on the lathe.

The whole thing has the disadvantage that only the self-made nut fits on this axis. But then you still have the largest possible thread diameter, and you can use the variant with the next smaller thread than Plan-B if Plan-A does not work. You can also adjust the length of the self-made mother to your own wishes.

I have now ordered a piece of suitable 42CrMo4V steel. That is enough for nuts with 8.8 quality, which could be tightened with M16 threads with up to 230Nm. But I don't need such values ​​for the Ford by a long way, that's more than sufficient.



I just hope you all understand me and the online translator doesn't write so much nonsense.

Greetings Andy

[Synchro909]

Originally Posted by DRG-ler

In advance I will go a completely different way. The tip came from a neighbor who drives an old Adler convertible from 1936. He gave me the tip to first cut the original thread so that it is clean again. Then the thread cutting die is cut and made tighter. With this tighter setting, the thread on the axle is recut again and again until the thread turns look clean again.

With this setting of the die, a thread mandrel is cut, which then has the same thread as the one on the axis. And this threaded mandrel is used as a gauge to turn a completely new nut made of hexagonal steel on the lathe.

The whole thing has the disadvantage that only the self-made nut fits on this axis. But then you still have the largest possible thread diameter, and you can use the variant with the next smaller thread than Plan-B if Plan-A does not work. You can also adjust the length of the self-made mother to your own wishes.

I have now ordered a piece of suitable 42CrMo4V steel. That is enough for nuts with 8.8 quality, which could be tightened with M16 threads with up to 230Nm. But I don't need such values ​​for the Ford by a long way, that's more than sufficient.



I just hope you all understand me and the online translator doesn't write so much nonsense.

Greetings Andy

I had considered this option also. It makes a lot of sense. The only negative is that the nut for that axle will be different from any other and must not be mixed.