Blew up another CV joint..., What to do? Options

[yarin]

So I need some advice on this one:

2 years ago a CV went on me during an autocross, drivers inside (tranny side). The bearing race cracked and well, u know what happens then, no power transmitted means flatbed tow truck home. Replaced all 4 CVs with the kit from PMB performance.

All was well.... fast forward to today, the exact same joint blew. I haven't dissasembled for a post mortem but it isn't pretty. Luckily i flat tow the car to events now so getting home wasn't a problem. The car definitely took a beating today, put about 45 total runs (autox school x 2 drivers) on the car before it let go on Avon Tech RA tires, a few areas of the course induced some slip/grip stress.

Motor is relatively stock, probably putting out about 100-110hp crank. AutoX definitely put exess wear and tear on the part, running semi-sticky tires.

So what should I do, replace with another kit? OEM? Beef it up with 944 or heavy duty CVs? Any of you fellow autoxers have a solution that won't cost me a fortune?

Thanks!

[Eric_Shea]

Ok Eric. I am going back to the welding thing I do now!

Alright, alright... so you know everything! (anybody else hate this guy? Welds like he does, knows all this $hit, has all the cool tools... can devour entire bags of Reeses Pieces in a single bound (IMG:style_emoticons/default/dry.gif) ) You should write a book... (IMG:style_emoticons/default/biggrin.gif)

Seriously, thanks Jeff. That's about as good-a-info we've gotten so far.

What I got, plugging in Yarins autocrossing as the general use, is:

The first 2 gears will have highest load on CV's.

Not too many autocross courses that get beyond those two gears.

Thanks Joe... I'm wondering (goofy thought); could it be the older CV's that Joe put in have "polished themselves" a bit through the wear cycle of normal use? (IMG:style_emoticons/default/confused24.gif)

[Jeff Hail]

Ok Eric. I am going back to the welding thing I do now!

(anybody else hate this guy?)

One more thing. The 914's sheetmetal suspension ears are very prone to lateral movement under cornering loads. If the ears are allowed to teater in and out on side load the entire axle assembly will follow. What does this mean? Axle moves in and out. High range of misalignment is designed into the CV assembly although the cage itself does not allow for that much lateral play. The result may be the ball trying to escape its confinement and popping the cage apart. So why did it pop?

Erics your analysis on the prior page shows a good eye for the wear found on the inner race. The cage showed very little contact wear at the cracked area. This can be from a lowered car on the bump stops while corning. Throw in some lateral movement on the trailing arm and kaboom. I do also see two burrs, one on the outer housing to the point where the edge is rolled. The other is on the inner cage at the crack. Notice is right between the bearing reliefs on both parts? Need to figure out primary cause and secondary damage from the failure. I tend to sway towards trailing arm moving in and out under load. More so as it was the inner CV that went away.

To help understand the dynamics of a CV in action the first picture shows all parts at rest in a straight line. No stress's. Doesnt really matter whether is an inner or outer CV as the dynamics are the same.

The second pic shows an exaggerated angle of attack for the axle shaft and inner race in relation to the cage and outer housing. This would apply to a lowered car. If excessive lateral movement of the outer housing occurs (trailing arm goes in/out on cornering/ acceleration load) the cage will pop.

[ericread]

Ok Eric. I am going back to the welding thing I do now!

(anybody else hate this guy?)

One more thing. The 914's sheetmetal suspension ears are very prone to lateral movement under cornering loads. If the ears are allowed to teater in and out on side load the entire axle assembly will follow. What does this mean? Axle moves in and out. High range of misalignment is designed into the CV assembly although the cage itself does not allow for that much lateral play. The result may be the ball trying to escape its confinement and popping the cage apart. So why did it pop?

Erics your analysis on the prior page shows a good eye for the wear found on the inner race. The cage showed very little contact wear at the cracked area. This can be from a lowered car on the bump stops while corning. Throw in some lateral movement on the trailing arm and kaboom. I do also see two burrs, one on the outer housing to the point where the edge is rolled. The other is on the inner cage at the crack. Notice is right between the bearing reliefs on both parts? Need to figure out primary cause and secondary damage from the failure. I tend to sway towards trailing arm moving in and out under load. More so as it was the inner CV that went away.

To help understand the dynamics of a CV in action the first picture shows all parts at rest in a straight line. No stress's. Doesnt really matter whether is an inner or outer CV as the dynamics are the same.

The second pic shows an exaggerated angle of attack for the axle shaft and inner race in relation to the cage and outer housing. This would apply to a lowered car. If excessive lateral movement of the outer housing occurs (trailing arm goes in/out on cornering/ acceleration load) the cage will pop.

WOW! Welcome to CSI-Jeff Hail!!! (IMG:style_emoticons/default/smilie_pokal.gif)

Until I read this I figured the Butler did it with a Candlestick in the Library... (IMG:style_emoticons/default/confused24.gif)