Broke rear half shaft TWICE within a month and a half... WTF?!

[SiCKS1D3R]

Yes, my passenger rear half shaft broke TWICE within a month and a half ( the same side in both cases ). It broke at the end where the nut is located. In the first incident, I had to tighten the nut ( 250ft-lbs ) after noticing it was loose during a rear brake job. Then a week later I happened to notice my center cap missing. Next thing you know I noticed the end of the half shaft when the nut is located is completely broken off :nonono: ( I replaced it ) . In the 2nd incident ( a month later ), I was doing an oil change and decided to make sure both rear nuts are tight. They were however, a few days later I noticed the SAME THING; center cap missing, half shaft nut broke off. Can any of you knowledgeable gentlemen shed some light on this sh1tty situation? I purchased a built SRA but won't be installing it until my stroker motor is complete, so in the meantime it'll be nice to have an operable Cobra.

Here's a pic:

 

[SiCKS1D3R]

Could it be the splines in the hub are shot?

 

[333arod333]

It might be the splines in the hub as you mentioned. It is not grabbing at the hub and spinning the nut free when vehicle is moving forward. Just check it out.

I just changed a wheel bearing on another car (RWD) and this theory seems plausible. There was also a lock nut and cotter pin holding axle nut onto the axle, but I see how if the splines in the hub were damaged it would just use the natural motion of the forward moving vehicle to loosen the axle nut and it would eventually come right off.

Idk how this would explain the end of the shaft breaking off though...

 

[SiCKS1D3R]

Appreciate the feedback. I just purchased a wheel bearing, not I'm in the process of purchasing a new rear hub.

 

[SVT_Troy]

side note, were you using the same torque wrench? Is it possible that it is far out of calibration and over tightening?

Bad hub mixed with wheel hop is more plausible though. Tq wrench is just something else to consider.

 

[ac427cobra]

I am also of the theory that the hub, could possibly be so badly worn, most likely from running with a loose halfshaft retaining nut, that this could possibly be causing the halfshaft breakage issue.

I'd replace the hub, FT 6550, the bearing, FT 6600 and nut, FT 6500. All of which can be found on our web site:

FTBR Mustang Cobra IRS Parts

:thumbsup::coolman::beer:

 

[SiCKS1D3R]

side note, were you using the same torque wrench? Is it possible that it is far out of calibration and over tightening?

Bad hub mixed with wheel hop is more plausible though. Tq wrench is just something else to consider.

Indeed I was using the same torque wrench. Appreciate the response.

I am also of the theory that the hub, could possibly be so badly worn, most likely from running with a loose halfshaft retaining nut, that this could possibly be causing the halfshaft breakage issue.

I'd replace the hub, FT 6550, the bearing, FT 6600 and nut, FT 6500. All of which can be found on our web site:

FTBR Mustang Cobra IRS Parts

:thumbsup::coolman::beer:

Alright cool, thank you! :rockon: