CV Joint -- Cage disintegrates at the track

[Jack Olsen]

They say 'power corrupts,' and apparently too much power corrupts constant-velocity joints.



Here are the balls, cage and stub of my CV joint -- a tribute to the tenacity of my limited slip and the new power from my Steve Wong chipped motor. The joint gave up in the second lap of the recent Roger Grago Benefit track day at Streets of Willow. It led to me finally being able to use my Triple-A Premiere membership for a free 90-mile tow.

The new engine is more powerful -- but not that much more powerful. I'm sure the CV joint was near the end of its life and would have given up with the old engine too. It had six years of service in a chassis with the engine and transaxle moved forward enough to make the angle of the axles pretty extreme. In the future, I'll periodically flip the axles from side to side -- or come up with some other long-term solution that doesn't involve the $3000-a-pop Porsche Motorsport units.

[Tim K]

Yikes. Did it just - let go? Or was there some indication that there was a problem?

Maybe Steve could make you a 'CV Saver chip'.

Tim K

[Jack Olsen]

It happened during a relatively slow turn, and the axle itself didn't break loose -- so there was no collateral damage at all. I was able to get back to the pits because the car's got a limited slip.

[KTL]

Great story Jack. Good to see you got the major bugs sorted out and ended up with a solid donor engine. Sorry to see you got skunked a bit. Unfortunately the longer you're around, the odds increase of running into a fellow of questionable character. Just ask Chris Streit about his G50 conversion a few years back..... I partly felt the pain of that one because I was the one who pointed Chris to the guy with the trans!

Anywho, wow often were the axles serviced? A high quality grease is key to CV joint survival. If you got six years out of them, i'd say that's pretty good if you never repacked them with new grease and put them thru all that abuse!

It's good that you got back to the pits but i'd just putter yourself to someplace safe on the track next time. No reason to put that kind of wear on your diff plates if you don't have to? Certainly I defer to your judgment, since you were there and I am just armchair QB-ing with no idea how much work it did or didn't take you to get off the track. Just saying that when one axle is asploded like that and the diff is doing all the work to make the other axle go, it's taking a lot of abuse. At slow crawl speeds, I suspect you just had to get the car moving and coast alot?

[AlfonsoR]

KTL or others, what's the recommended grease for the CV joints?

[Bill Verburg]

Originally Posted by AlfonsoR

KTL or others, what's the recommended grease for the CV joints?

Krytox for track use

[304065]

Krytox. Bill beat me to it. It is the only grease that can hold up to the punishment. It's expensive as hell, makes German Klueber grease look like the stuff from the FLAPS.

Some guys duct air to the CVs also through a NACA duct. The NACA is widely misunderstood, it's intended to be an air inlet that doesn't disrupt the boundary layer, not a high-pressure inlet, so I think you could just use a big aerodynamically dirty scoop and keep those suckers cool.

[Jack Olsen]

Originally Posted by Warren Hall, Jr

Never in the past 38 years have I needed a torque wrench for VW or Porsche axle nuts, and I have always used 3/4" drive tools and large 4' - 5' pipe extensions ... after I twisted off the hinged drive link on an 18" Craftsman 1/2" breaker bar and returned it for free replacement in 1968!

Your weight, and a calculator or slide rule [no batteries to fail] can get you to the proper location on an extension pipe to lean on ... for proper torquing upon reinstalling that axle nut! Never had a problem with stripping threads or nuts coming off, either!

I'd like to avoid having to buy a 3/4" torque wrench. So now that I've split this off into its own thread, can someone explain how I could use my 160# self and an extension to get close to the spec of 340 ft-lbs. (And is that number correct?) I'm guessing (based on an old post I read) I could step on a bathroom scale, press down on the horizontal bar four feet out from center until my 160 pounds reads 75 pounds, which would mean Im applying 85 lbs of downward force, which multiplies with the four-foot length to give me 340 pounds of torque?

Yes or no? Please understand that I speak very little 'math' but that the earth's gravitational pull on me appears to be very reliable and constant.

Also, the inner set of six bolts gets torqued to 34 ft-lbs, correct?

[rusnak]

Box pipe, or galvanized fencepost.

I understand Krytox is pretty nasty stuff, and you need even nastier stuff to clean it up.

[gtc]

Your torque wrench math is correct.

Edit: what CVs and axle flanges do you have?
33 ft/lbs for M8 CV bolts, 60 ft/lbs for M10.

[RWebb]

P AG should hire you as a beta tester, Jack

[Jack Olsen]

Thanks Graham. I think the M10 bolts are for the four-bolt configuration, and the M8s are for the six-bolt. [Edit: I think I'm wrong about that.]

Randy, I think Porsche AG should send me a pair of those $3,000 axles. And a spare.

[Grady Clay]

Jack,

What CV joints do you have?
M8 or M10 bolts? 100 mm or 108 mm diameter? What 'thickness'?

How far forward is the c/l of the transmission flange from the stub axle flange?
What is the angle of the axle?

Best,
grady

[Jack Olsen]

M10 bolts. It's the 85.5-89 Löbro axle. (So it looks like 60 ft-lbs of torque for the bolts.)

The engine has been nudged forward. A very rough measurement of the axle angle yields 5° off of perpendicular.

[slodave]

I dunno. A little JB weld, buff it out and you should good to go.

[TRE Cup]

Here is my recipe , without getting too many $$ into it

As we discussed at SOW, you have the trans shifted forward in the chassis. This adds more angulation, hence load , on the cv's. There are chrome moly cages that we source from off road specialists that have more room to allow more angle on the joints. New joints should be disassembled, the inner and outer channels polished, the stock cages thrown away . Test assemble dry and the balls should float nice and loose in the assemblies.
Take them apart, put on two sets of latex gloves, and apply Krytox. The stuff stains skin like you wouldn't believe !
Reassemble, install, torque to spec, go drive about 100 miles on the street, recheck torque.
Enjoy
Now this is not cheap, but these will last you a very long time.

Or, you can take the "what the heck " approach, where you buy rebuilts and replace them every X amt of hours

Trust me, you would not want an axle breaking loose and windmilling back there; it can be dangerous !
Been there, experienced turn one driver's left wall at Riverside, when a buddy asked me to try out his car. Wasn't pretty

[na2ub]

I believe 2 feet with your whole body weight would give you 320 ft / lbs, and another 1.5 inches (.125 feet and .125 of your weight) would give you the extra 20 lbs. Alternatively, a lot of the auto stores have "loaner" tools that you can use for almost free (I had to pay tax last time).

Good luck. That really sucks but at least it did not tear up the underside of your car.

Doug

[HawgRyder]

Doug is correct....torque is measured in foot-pounds....so if the wrench is 24" long and you apply 100 lbs to the end of it ...you get 200 lbs of torque.
In the aircraft industry and also with big trucks....there are extensions that fit on the square end of the torque wrench to lengthen the over all tool.
you need to get one of those extensions and put it on your torque wrench or Johnson bar to give the correct length as per the amount of weight you are applying.
Or....get a REALLY big hammer....LOL
go for it Jack
Bob

[MBruns]

Be careful when dealing with that grease, wear gloves, do it outside, it is awful on clean up, and its as of earlier this year over 300.00 U.S. per pound, it used to be 125. per and that was bad enough, But its the best for that duty as well as wheel brgs. for endurance racing

Mike Bruns JBRacing.com

[Green 912]

They sell a solvent for Krytox. Recommend you get it along with the grease if you plan to use it. Krytox is not soluble in standard solvents water or petroleum based. It is a mild irritant to skin per the MSDS and don't even think about getting near your eyes. Gloves, disposable work area cover and old / disposable clothing. What it gets on should be discarded, not washed. It is fluorine based and gasses off some real nasty stuff at high temps. If you blow a CV and it gets spit on the headers stay away until the surfaces are cold.

Older type open ended CV joints are a bear to pack and install cleanly.