Differential Axle Shaft Snap Broken

[cengrtecs]

Good day!

Is there anyone of you who can suggest of how I will weld for the third time a snap differential axle shaft of my pick up. I have bought that converted pick up from somewhere and only found out that they cut short the differential to narrow the track on the rear, not original one. Shaft was cut halfway and welded. Understood that twisting force cause it to break.

What I did before was to have it repaired 2 times on a nearby shop. As I have seen it, they make a 40 deg total (more or less) V cut on both ends of shaft, welded and trued again. I have doubt that they did not used specified welding rods suitable for shaft material. Is post heat treatment necessary? Your suggestions are very much appreciated.

Merry X'mas,
Cengrtecs

 

[Fabrico]

Proper welding would involve a significant heat treating process. But even with that, you will never be able to attain full strength or resiliency.

I would break the other one too and mark all the pieces. That way you could use a shorter box when you ship them to a good axle maker for replacement. Problem solved forever.

 

[MikeHalloran]

Chances are your welds were as good as anyone could make them, but that's not enough.

Most axle shafts are induction hardened to develop a precisely controlled thickness of hard case over a tough core. The process cannot be duplicated by the average blacksmith or machine shop.

Just buy the proper shafts. Drag racing has put a lot of companies in the custom axle business, so they won't even be particularly expensive. You just need to give them a few key dimensions, and they'll take it from there.



Mike Halloran
Pembroke Pines, FL, USA

 

[cengrtecs]

Thanks to both of you for your replies. Yes! I noticed that when they trued them on a lathe, outside surface is harder than the inner core. Understood, original strength can not be attained after repair but my present purpose is to move the car from one place to another until a proper replacement is found.

I will try to look for an axle maker as you have suggested so to release me of my worries.

Best regards,
cengrtecs

 

[MikeHalloran]

Look in the back of Hot Rod magazine.



Mike Halloran
Pembroke Pines, FL, USA

 

[MechanicalChef]

"I noticed that when they trued them on a lathe,"

Does this strike anyone else as a bad idea? Now I'm not in the business of making driveshafts, but I have a hard time wrapping my brain around the benefits of straightening a drive-shaft by removing material. Plus cutting down the welds probably removed a large portion of the strength gained from welding it in the first place.

 

[MikeHalloran]

I'm assuming the shop put each half of the axle shaft in a lathe to cut out the broken weld metal and cut half of a v-groove for a repair weld.

It wouldn't make much sense to remove metal after welding, unless the shaft has to pass through some small clearance. Most axles wouldn't need it, but maybe that unnamed one does.





Mike Halloran
Pembroke Pines, FL, USA

 

[TheBlacksmith]

Axle shafts take a lot, but properly made, that can take it. I can remember the old drag racers using dykem blue and a scribe to mark a straight line along the shaft; when the ends were out of sync (twisted) 180 degress, they'd replace them. I don't see welding coming near that strength. Mike is right, buy some from one of the shops that specializes in custom axles.

 

[Rob45]

Most Ford 9" axles for example would require passing through a bearing and bearing retainer.

But I've got to ask:
Is this an engineering question, or one for some auto mechanics forum somewhere?

 

[MechanicalChef]

Referencing the original question, "Is post heat treatment necessary?" I'd surmise a typical engineer would know more about heat-treatments than your typical grease-monkey.