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!

[Crazyhippy]

I've put 400+HP through the Renegade Hybrids setup. Sticky street tires and AX, track time and lots of street miles.

Down side to big CV's is, the Trans is the next week link.

BJH (Former renegade employee just being up-front)

[McMark]

We definitely need some pictures and a postmortem write up. I lost a CV and I'll be curious to see if this is the same failure.

(IMG:style_emoticons/default/thisthreadisworthlesswithoutpics.gif)

[Eric_Shea]

I lost a CV and I'll be curious to see if this is the same failure.

Me too. (IMG:style_emoticons/default/blink.gif)

[Jeff Hail]

I lost a CV and I'll be curious to see if this is the same failure.

Me too. (IMG:style_emoticons/default/blink.gif)

Did you get your CV from that Shea guy Eric? (IMG:style_emoticons/default/av-943.gif)

[yarin]

I lost a CV and I'll be curious to see if this is the same failure.

Me too. (IMG:style_emoticons/default/blink.gif)

Did you get your CV from that Shea guy Eric? (IMG:style_emoticons/default/av-943.gif)

Yes, Eric took care of all 4, great kit that helped get me back on the road. I'm wondering if generally speaking those CVs aren't built to stand up to autoX use... will break down and take pics today. The contents on the CV might be shredded since i flat towed it home after. But i'll post pics to compare..

[davep]

Does that CV have the axle go to extreme angles a lot?
If so, then stiffening the rear to keep it flatter in turns may help.

[DNHunt]

Yarin

Sorry about the CV. What pressures are you running in those tires? I have a set too.

Dave

[yarin]

Here are pics. The bearing race cracked, exact same failure mode as last time (2 years ago).

Dave - running 24-26 psi hot.

Can anyone think of why the same CV failed? Is there something specific to torque distribution or the way the diff works that would cause the left side to go first? Could it be generally related to the clockwise nature of the autox course?

Strange.. Anyhow, i feel like if i replace it with another kit, it will fail again, just a question of when.

I'm sure this wouldn't be a problem for a street car, R compound tires + autox put a fair amount of strain on the joints. The lots we run in tend to have slight humps leading to the rear end getting light and tires slipping under accel. Combine that with a few spins here and there... boom.

(IMG:style_emoticons/default/blink.gif)

[ericread]

I lost a CV and I'll be curious to see if this is the same failure.

Me too. (IMG:style_emoticons/default/blink.gif)

Did you get your CV from that Shea guy Eric? (IMG:style_emoticons/default/av-943.gif)

Yes, Eric took care of all 4, great kit that helped get me back on the road. I'm wondering if generally speaking those CVs aren't built to stand up to autoX use... will break down and take pics today. The contents on the CV might be shredded since i flat towed it home after. But i'll post pics to compare..

(IMG:style_emoticons/default/popcorn[1].gif)

Oh, Eric Shea??? Are you out there???

[yarin]

The rear is pretty flat during cornering, suspension is rather stiff. I don't believe excess sway is the issue.

Also tires are 205/50/15, not running some massive sticky tires here either..

Correct me if i'm wrong, but isn't this a common failure on these cars?

[Eric_Shea]

I'm wondering if generally speaking those CVs aren't built to stand up to autoX use... will break down and take pics today. The contents on the CV might be shredded since i flat towed it home after. But i'll post pics to compare..

Mark and I had been investigating an incedent where, on his way out to RRC last year, his CV inner cage snapped. These are the only two failures we've seen out of now roughly 100 CV's. Mark's situation was a little "interesting" but not beyond what others could encounter. He was pulling out of an entrance apron which allowed one wheel to extend while accelerating.

When the gang arrived here I gave him a new CV and we looked at the extension of the inner race and cage. Andy, being fresh off the Rubics CV puzzle said he thought they extended further than he had seen before.

Those CV's were disassambled/machined and then reassembled. We wondered if the inner race may have been installed the same upon reassembly. I don't believe we ever got the answer to that but, after digging into it we felt it was just a fluke.

We now machine the CV's assembled and tape the entire surface to avoid metal shavings etc. I've checked the CV's out of the box and they don't seem to hyperextend.

Bottom line: With a 2% failure rate and given the application of serious autocrossing with slicks etc. I'm not sure which way to go here... I want to know what happened so we can asses if this will be a future problem but, I don't see this as somthing that will affect others.

There have been some really good answers herein as well. You could get larger CV's (Bus axles, 911 axles w/spacers etc.) but, CV's are relatively cheap compared to transmissions.

PM me your info and I'll send another CV kit out today N/C. (IMG:style_emoticons/default/wink.gif) Make sure you use all the grease and torq everything properly etc. Sounds like this may have been another one-off (hoping).

E.

P.S. Silence Jeff! Back to that welding thing you do... now! (IMG:style_emoticons/default/tongue.gif)

[Eric_Shea]

Correct me if i'm wrong, but isn't this a common failure on these cars?

Yes and No. Some cars still have their stock CV's.

Are 914 CV's "robust"? Not really. Again, given your application, I'm not sure which way I'd go. I would think you could easily go 5-6 years w/o a CV failure while the normal driver could go 10-20 (or longer).

(Mr. Read... how'm I doing? (IMG:style_emoticons/default/popcorn[1].gif) )

[yarin]

Correct me if i'm wrong, but isn't this a common failure on these cars?

Yes and No. Some cars still have their stock CV's.

Are 914 CV's "robust"? Not really. Again, given your application, I'm not sure which way I'd go. I would think you could easily go 5-6 years w/o a CV failure while the normal driver could go 10-20 (or longer).

(Mr. Read... how'm I doing? (IMG:style_emoticons/default/popcorn[1].gif) )

Makes sense...

Just sent u a PM. Thanks for chiming in! Hope this is just a fluke, looks like i'll be able to get back on the road within a week.

Thanks Eric!

[Eric_Shea]

These are areas of concern that I see:

Looks like the inner race was rubbing on the cage:


Looks to be confirmed here:

[ericread]

Correct me if i'm wrong, but isn't this a common failure on these cars?

Yes and No. Some cars still have their stock CV's.

Are 914 CV's "robust"? Not really. Again, given your application, I'm not sure which way I'd go. I would think you could easily go 5-6 years w/o a CV failure while the normal driver could go 10-20 (or longer).

(Mr. Read... how'm I doing? (IMG:style_emoticons/default/popcorn[1].gif) )

Eric Shea;

Great reply. I know how important your reputation is to you, and before anyone else started guessing what happened, I thought you should chime in. We all look forward to the improvements you and the other 914 innovators make to modernize our 35 year old components. So, have you considered manufacturing two-levels of CV joints? One for the daily driver and a beefed-up set for the racer/AXer? Or does the racer/AXer just exaggerate the DD forces, so that a single CV type will meet the needs of both?

Thanks for your speedy reply, and have a great holiday weekend.

[yarin]

Keep in mind that after the CV failed, it was flat towed (4 wheels on the ground) in neutral about 50 miles. So the drive shaft was spinning within the broken bearing race. That may have causeds the signs of wear that you see. Made a not so friendly metallic failure noise all the way home...

[Katmanken]

Couple of thoughts..

The beetle cv's don't have as great an angle of operation as the 914 cv's...

That is, the up and down travel of the wheel is less with the beetle cv's.

If you measure the axle length and the amount you can move the wheel end of the axle up, you can do a little trig and get an angle of operation. If the angle measures more than the allowable operating angle,there is a clue.

Another thought- looking at the crack, inward loading of the shaft on the cv race might load the slot in the race to produce the crack as shown.

It does look like a fatigue crack that propagated. Look for nicks at either end of the crack- that's where they start. Starting end of the crack can have wear from rubbing together

The other though is around modern crap. Some of the products made today are NOT the products of yesterday. Those parts were made made with fanaticism to produce a reliable part. Today it's nick on the part? use it... Heat treat? who cares if it's a little off, Poison in the drugs? Ship it... Poison in the pet food? Ship the product...

Ken

[Eric_Shea]

So, have you considered manufacturing two-levels of CV joints?

We don't mfg. the joints. We machine 2 of the 6 bolt holes to fit the roll pins.

I currently have 4 new bus axles here that we are now looking for a new machine shop to manufacture the adapters. This kit was going to be around $499.00 complete (axles, adapters etc.). One set is actually pre-sold to a very patient customer who has been waiting for the adapter machining process.

Once these are done this will be a bolt on solution for the more agressive 914 or higher HP applications.

[Eric_Shea]

Made a not so friendly metallic failure noise all the way home...

That makes a ton of sense... forgot about that. OK. CV kit is already packed with a label on the box. Enjoy. Sorry for the problem.