And most of them either broke in the keyway, or at the end of the taper. A high stress area. Bob

Yep

I think it has more to do with heat. I've never broke one on rr always the lr . The heat from the header and brake will turn the axle to a copper color. I think its to much for the axle and pulls some of the strength out of it. We run turn outs on the headers to keep the heat to a minimum.

Re: What causes the RR axles to shear off?
 

That sounds like a good idea. :6:

Re: What causes the RR axles to shear off?
 

I cut a lot of sheet aluminum and since I can't afford a $1200 stomp shear I clamp the sheet in my break, drag a box cutter blade across it a couple times and bend it. Some of the cheaper softer alloys need to be bent back and forth 2-3 times to separate. The more expensive harder alloys such as 6061 and 7075 always snap clean on the first bend...usually at 45 degrees or less. It amazes me how easy the stuff separates once its continuity has been interrupted by a bit of a scratch.

I have always felt like one of the best indicators of a potential axle problem is an interruption in the anodize coloring. The reddish color on a winters, the purple on a Frankland (I think??) and the black on DMI axles are awesome because you can easily see the contrast of the raw aluminum color underneath. I can't remember which brand made gold anodize axles but you had to look a bit harder.

I don't worry so much when the color starts wearing off the splines where the wheels typically live as it is a very smooth, gradual change...almost like it's being polished off from constantly removing and moving wheels. When I see any sort of lateral scratch it gets frequent attention. When you see a scratch/groove running around the circumference, usually close to a birdcage, especially when they are an eighth inch wide and you can feel how deep they are with your finger, it's a good idea to find a replacement, at least for long enough to have yours inspected.

Driver riding the brake really puts the heat in the axle, that is the first thing I ck when my car is back in the pit, not by feel but with the temperature meter, it radiates out to the wheel and tire, sometimes really hot, but on a non wing, the RR gets the most bending action. Bob

If you go to any welding or a good body shop supply company they sell a spray that looks for cracks in aluminum I have it in my body shops to check all aluminum reinforcements you would be surprised how many we find cracked that you can't see any damage to

Overfilling the case with grease, no room for expansion thus seal pressure on axle surface , cutting into axle creating the shear points, Kreitz sells axle saver sleeves for this very easy fix

Re: What causes the RR axles to shear off?
 

That's right on Donnie. I bought 2 new rear-ends last year and I put the sleeves on before I ever ran them. And then I modified the venting by increasing vent tube size. That seal pressure is a killer.

Re: What causes the RR axles to shear off?
 

In my 35 plus years of spectating sprint car races, 25 plus races a year in the midwest, I think I can count on one hand the number of RR axle failures that I have seen. Is this a bigger problem elsewhere in the country? Or is my mind just gone? :10: