Why did my new cv boot split?
 

After 3-1/2 days of Club Race & DE last August & September, I recently discovered that I have a split CV boot on the driver's side, inboard.

The full story: Car is a 1988 Carrera dedicated track car. I ran stock exhaust for ~60 days of CR & DE over 3 years and then installed European Racing Headers last July. After 1 afternoon track day I had 2 split CV boots - Left inboard and Right outboard. The day was hot (98 degrees) and the boots were old (145K miles) so I bought and installed new GKN axle/CV assemblies from Pelican last July. Then I drove 2-1/2 day CR and 1 day DE in August & Sept before parking the car for the winter. Started work on it last month and discovered the Left inboard boot had split, apparently during my last driving session or two because grease was all over (cleaned up before the photo).

Has anyone experienced bad GKN CV Boots?
Has anyone had problems with boots after installing headers?


http://forums.pelicanparts.com/uploa...1296327059.jpg
http://forums.pelicanparts.com/uploa...1296327081.jpg

Some suggest that when lifting the car with clamps on the small part of the boot it could cause tearing.

Some recommend not using the clamps on the small end.


http://forums.pelicanparts.com/porsche-911-technical-forum/210117-cv-joint-boot-clamps.html

http://forums.pelicanparts.com/porsche-911-technical-forum/395604-cv-boot-clamps-sc.html

Odd... I was prepared to say that the "Meyle" crap that's out there doesn't seem to have enough anti-ozoneate mixed into the rubber compound but I've never experienced that with GKN/Loebro products.

Also….
The boot is very close to the outer radius-of-bend of the exhaust header pipe.
The outer radius of a bend is the hottest part of the pipe.
With a heat exchanger, there is little radiant heat directed to the boot.
Without the intervening metal, I suspect the temperature of the pipe could be in the range orange-yellow 2800-3200°K.

http://forums.pelicanparts.com/uploa...1296331166.jpg
2800-3200°K = 2527-2927°C, 4580-5300°F
1800°K = 1527°C, 2781°F
HOT


Depending on the air flow, that could ‘cook’ the boot.

I would clamp a small ‘shield’ between the outside radius of the pipe and the boot.
You might consider some other radiant heat and hot air deflectors.

Best,
Grady

The best solution I've found is coating the headers with a ceramic-metallic thermal barrier material as that makes a very noticable difference in radiated heat.

We have them done both inside and outside to contain the heat inside the pipes.

Where did you get them?

Steve's right - the radiated heat difference is absolutely stunning. The temperature difference is so dramatic that you can do quick finger touches (on a street car) while the engine is running (even after it's been on a long drive). There is no way on the planet that you could do that without coated headers. The smell of your frying skin and your piercing girlish shrieks would inform everyone around of the difference - LOL!

Besides, it looks very nice.

angela

Thank you all very much for your thoughts.
I'm going to look into coatings.

Prost!
Bruce

I bought them from Pelican.

I would give Scott Pelican Parts Technical BBS - View Profile: Scott at Pelican Parts
a ‘heads up’.
It is this kind of feedback that keeps Pelican the best.

Best,
Grady

Good idea Grady. Will do.
Thanks,
Bruce

It's not a pelican parts issue

I have issue with same design CV's on my car over the years and i don't clamp the small end

it seems as soon as i put the car up on my lift the cv may split after it's 1 or 2 years old.. and it's not my daily ride. The small end does not ride up past the axle lip when lifted and I've been tempted to push the rubber past the lip before lifting but have never done it. It happened once after being jacked up out west and the only saving grace was i didn't lose and grease due to the grease I use sticks like glue. Granted the car never saw over 90 mph on the next 5k+ miles ride home

I've had 2 of those happen on my 88 last year, both on the outboard boot, 1 on each side. Both axles were replaced in 2009, so the parts were approx. 1 year old, 5 to 7K miles. I think GKN used a batch of crap boots, but that's just my opinion. I sent GKN a complaint, and was told to send the afflicted boots back to the place where I bought the axles (Pelican). Seeing as how shipping the parts back ends up the same price as a replacement boot kit, and doesn't actually get me a replacement boot kit, I just ordered the boot kits ...

At least the inner boot is somewhat easier to replace!

I have had very good results with generic one size can be trimmed to fit all boots. I used to get them from NAPA, but last time I checked there they were no longer carried. So I used a mail order place (JC is first initial, W is last) which had them. To use them you need the style of CV stamped steel end piece to which the boot rubber is attached by a clamp.

I don't know just how one would convert to this style, as the ones I have are many years old. They are not the kind where the CV end of the rubber is rolled into the sheet metal. But on looking again at Bruce's photos, I see he has just the right kind for this. So I'd for sure use these generic ones to replace the busted ones. Much less expensive.

I have taken to using a Carroll Smith idea for the small end of the boot: stick a small plastic tube (snipped from a used up brake clean aerosol can) under the lip, and tie wrap it all. The idea is to allow the air pressure changes as the boot expands and contracts to pass through the tube, so basically it doesn't exist. I see Bruce used the steel clamps on the small ends too. I don't have an opinion on that causing extra strain on the rubber, but there really is no reason to have that end so tightly clamped. Perhaps if yhou plan to ford streams that deep?

I've run the standard inexpensive brand of race headers (not Georges) for years with no effect I could see on boot life (which has been pretty good), and I think they come fairly close to things. So I am a bit dubious about the heat theory. But of course it could be a factor in premature boot failure.

Walt (in transit at Paducah, KY)

Excellent! It looks like generic boots with vent tubes, coated headers and a heat shield all together should improve the life of my boots greatly.
Thanks again to all.
(Walt, I'll try to keep it out of the water!)

Prost!
Bruce

I'm wondering if there's something the boots can be regularly treated/maintained with to extend their life (e.g. rubber/vinyl conditioner)?

If I have to re-do my CV's again because of a split boot, I'm gonna kill someone (mainly myself!).

RMR,
I showed this thread to the supplier who provides us with the GKN boots. He said that the boots are good for stock use, but your modified car and track use is probably more than they can handle. Fortunately, you have some of the top guys on this forum suggesting solutions. Good luck!

- Scott

I see no other mods besides headers. Right? I mean if the trans is moved up and the angle on the CV is odd or there is a mod that could cause this?

Just because it's on the track doesn't mean that stock CV boots should be failing. Porsche has the rep of being able to go from the street to track and back to street with minimal mods. The answer from GKN isn't very satisfactory.

Had the same exact thing happen to the inner joint of both of my new GKN driveshafts last year. I have B&B heat exchangers, which have a significant amount of exposed exhaust piping. The EMPI replacements boots from our host seem much more substantial...

I've got no mods on my car at all. Even stock ride height. So the 'track use' excuse doesn't work for me...

And the outer boots split for me, so heat isn't to blame. Looks like the OP's split started on the inside fold right at the mold line (same as on both of my boots) - if exhaust heat were to blame, seems like the outside tip would be more likely to go - the inside fold is rather shaded.

My split boot (both looked the same)
To be clear, the boots that split on me came with the new axles. I don't have any gripes with the boot kit (yet).
http://forums.pelicanparts.com/uploa...1296600966.jpg

some of the Vanagoneers among us have no doubt seen people on Samba complaining about cheap boots

it may be that Chinese Drywall Disease has reached GKN...

As I opined....GKN is passing off a defect in the boot to "use on the track". It's an excuse and not a good one. The BIG issue is not the cost of the part but the cost and time of replacement. With the exception of tranny fluid, I hate dealing with CV grease the most.

I wonder where GKN makes the boots and if they recently changed molds or material mix.

Not necesarily the problem here but if you let the axle drop to fast and too far it will bend the boot mounting metal out of round. If you don't straighten it, it will put additional stress on the boot and will eventually tear it.

I wouldn't conclude that GKN is passing off a defect in the boot to use on the track - they might be, but that header set up is seriously hot.

IIRC, Steve W. has posted some sort of high zoot boot they use on race cars - probably cost about as much as a complete CV, but...

The GKN CVs (they seem maybe the only maker, as they are combined with Lobro per the box) I bought about two years ago were perplexing. The inner channels, which I recall from past replacements as being very smooth, if not as polished as, say, the balls, were striated. The body was silver instead of a dark uniform color, except where it was blue, which appeared to be where the steel was heat treated (maybe just fine, treatment would be needed only on the wear surfaces).

But the biggest disappointment was the cage. Balls are supposed to pop into their grooves, and stay there. These new cages were like old, worn cages - the balls would just slip through.

I don't know if this is really going to affect anything. Tight cages are something others have said are necessary for a CV, and loose ones a sign of a CV which is worn and needs replacement. I don't know how important cage fit really is. Mine have run OK, but I don't place any long term faith in that observation, as the hours aren't high enough.

So maybe there is an overall decline in quality here, both in boots as well as the CVs?

I had a period where the CV boots would tear for no reason once a year. Replacing them is a huge PITA. I got fed up and ended up replacing the CV's entirely with new CV's and half shafts. That was about 5 years ago and no tears.

My logic was that perhaps the CV's were warn and creating internal heat that was causing the boots to tear.

Either way, glad I don't have to "mess" with them any more.

Chris

73 911 E

[QUOTE=burgermeister;5820931]I've got no mods on my car at all. Even stock ride height. So the 'track use' excuse doesn't work for me...

And the outer boots split for me, so heat isn't to blame. Looks like the OP's split started on the inside fold right at the mold line (same as on both of my boots) - if exhaust heat were to blame, seems like the outside tip would be more likely to go - the inside fold is rather shaded.

My split boot (both looked the same)
To be clear, the boots that split on me came with the new axles. I don't have any gripes with the boot kit (yet).QUOTE]

burgermeister,
Did you get the EMPI kit(s) from Pelican? (PN 000-043-301-08-M84)
Last July Pelican did not offer just CV Boots for Carreras/G50 cars, which are different than 915s, they only sold axle assys. This "new" EMPI kit says '85 through '89 with 915 trans. Of course this is out of whack since the G50 started in '87. If not from Pelican, where did you get them?

Thanks,
Bruce

I was talking to a friend at work about my CV boots tearing and he said he's seen some sort of kevlar(?) "overboot" used in some offroad ATVs on their rubber CV boots. He rides dirt bikes a lot and comes across these guys on ATVs and they don't want a boot tear out in the boonies to ruin a part while they try to get it back to be repaired. Sounds like it may help out in our situation.

I kinda don't buy the heat argument either......the split is in the "valley". Let me ask this---> look at the failed CV boot photo. Does the overall *thickness* of the rubber.....on *that* unit.... look a bit "thin" to you, compared to what you might see as Porsche OEM ???

.... or could that just be an optical illusion?

burgermeister,
Did you get the EMPI kit(s) from Pelican? (PN 000-043-301-08-M84)
Last July Pelican did not offer just CV Boots for Carreras/G50 cars, which are different than 915s, they only sold axle assys. This "new" EMPI kit says '85 through '89 with 915 trans. Of course this is out of whack since the G50 started in '87. If not from Pelican, where did you get them?

Thanks,
Bruce[/QUOTE]

I got both a GKN & an EMPI kit from Pelican - they had both when I ordered. Replacing the outer boot took some creativity ...

I also have a spare axle now, and I've gotten good enough where I can swap one in about 1.5 hours.

Just as a followup, I had my driveline out last fall. Upon careful examination, all but 1 of the remaining GKN axle boots had small rips in them. Not all the way through yet, but definitely there. That's 5/6 within 2 years or 8,000 miles. 3 went within 4,000 miles.

All tears started at the inside corner of the biggest pleat, right at the parting line flash. All the boots had very coarse, large amounts of flash. The boots from the axles that came with the car, as well as the replacement GKN boots I had on hand, had only a very small mount of fine, consistent flash. So it might be a "we paid dongfeng rubber works to build boots to print" issue. I now have EMPI boots everywhere, I'll se how they hold up.

Replacing both boots on the axle is at most a 90 minute job (3 hours with removal / reinstallation, and that's for me, so it ought to be faster for normal people) IF the CV's don't have to be re-packed or disassembled, so it pays to catch them early.

http://forums.pelicanparts.com/uploa...1308608069.jpg
http://forums.pelicanparts.com/uploa...1308608091.jpg

burgermeister,
Thanks for the follow up and interesting observation about the crack starting at the mold flash.
I replaced my split boot with an EMPI boot (from Pelican) installed with a vent tube. Also have coated headers now. Racing plans delayed by gearbox problems but will post update after I get back on track.
BTW, I'm carrying a spare EMPI boot - hopefully to ward off the crack demons!

To add to this thread, I just bolted up a pair of new G50 axles (purchased from Pelican) last weekend, did a 2 day DE this weekend, and both of my inboard CV boots have split. I was under the car today checking things over and spotted grease all over the place...I can barely even see my starter in the mess. GKN/lobro really needs to do something about this.

Not sure which road to take: replacement GKN/lobro boots or an aftermarket option.

Slightly OT but I had to share my experience and give hope to those dreading the CV boot replacement chore.

Not for nothing but I have replaced the CV boots on my lady's Lexus. It took me less than an hour.

I used a very un-orthodox method of slipping the replacement boot on. It is ridiculously simple. I did not believe it until I did it.

Tools:

Large Long Black Funnel (found on the impulse shelf at a FLAPS)
K&N Filter Spray Oil (anything that is tacky)
(of Course tools needed for removal of wheel, rotor/hub etc...)

Removed torn CV boots and cleaned the CV's thoroughly with no-residue cleaner spray.

I modified the funnel to match the OD of the existing CV, smoothed out all edges. (This was part of the hour spent)

Sprayed oil on the funnel.

Placed the large end on the CV then firmly slipped on the inner boot "pop' it was on then repeated the oil and flipped the outer boot inside out then slipped that on too "pop" :D . You need to flip the outer one so the when it slips on, you can flip it back so the orientation will face wide part out. Trying to slip the small end over the CV is impossible, unless you have a press tool.

Wiped off the oil and packed with included CV lube, crimped the metal ties.

It was that easy.

It has been 4 months and tight as a bug.

Here is the video I watched in disbelief: http://www.youtube.com/watch?v=F17tFS6ofzU&feature=related