half shafts

[RushR.Rentals]

a customer brought us his rush car because it had no forward drive.
the outer CV let go in the right side I had some hopes to just do a rebuild but the inner race of the CV got so hot it turned it blue and welded itself to the half shaft that removing it in the press ( you shouldn't need a press to remove a CV ) ruined the splines of the half shaft so it's a total half shaft replacement.
seeing the right side failed I pulled the left side half shaft out cleaned all the nasty old grease out of both the inner and outer CV's repacked with high temp CV grease and reinstalled the half shaft back in the car.
the right side axle comes out in just a few minutes nothing on the suspension has to be unbolted other than the lower shock nut has to come off and the bolt pushed back some . the left side the nut on the top of the up right with the lower shock nut has to come off so the up right can flop away from the upper A arm.
takes about 2.5 hours for the hole job and 30$ for the high temp grease per side. for both CV's it took about 2/3's of a tub of grease.

 

[jlaughman22]

Any cause that you can see

 

[RushR.Rentals]

the car owner has done about 12 track days as far as I can tell the cause was old grease that failed to keep the CV properly lubricated
this lead to heat and bearing failure.
seeing this for our rentals I will be inspecting the CV's on a regular bases.
pulling the half shaft only takes about 10 minutes at most so definitely worth the few minutes it takes to inspect them.

going over my customers rush car I'm learning lots of what to inspect for a pre event inspection.
one other thing to inspect is the tops of the hem joints for the A-arms to the up rights. they tend to collect lots of dirt and crud being that there are no caps on them that sand and crap will get into the helm joint and lead to premature wear.

 

[John H]

one other thing to inspect is the tops of the hem joints for the A-arms to the up rights. they tend to collect lots of dirt and crud being that there are no caps on them that sand and crap will get into the helm joint and lead to premature wear.

I'll fix that.

 

[John H]

Is that what the CV looked like coming out? Looks dry as a bone. Were they finding and wiping sling constantly?

The container of Cv2 will pack 4 joints with a bit left over.

*Putting this here because I don't want to engage any longer but want the correct info available.

If the joint runs dry it's a leak. Be vigilant of leaks and address them when found. Intact boot means nothing, they leak from the flange (he'll figure it out eventually). Using more grease does not prevent this.

On the moot subject of how much grease to use in the joints. Mfg. spec of ~90g is plenty of grease, some hard empirical science: the holding capacity of the CV joint is 50ml, CV grease is typically ~1g/ml density, which CV2 is in fact. No calculator needed. So, the Mfg. spec of ~90 grams packs the joint completely with a loss factor and extra margin baked in.

The joint will never have more grease then when you first install it. Immediately when put in operation some grease in a fully packed joint will migrate out never to return. Adding more grease at the start just increases the amount outside of service. Additionally the stub shaft hollow is <15ml estimated. If you're following along, that's 65 grams maximum holding. So if you "use" 130 grams (trying to cure a failure that happened from a leak 🤷‍♂️ ) where does that other 65 grams fit/go? Either into the boot where it will forever stay out of service, or it was actually left on your table and hands, maybe all of the above... You can't make space where it doesn't exist. Where extra grease doesn't go is into service lubricating the joint.

 

[RushR.Rentals]

yes they were dry and not enough grease from the start.
in no way would I put as little grease as John stated this is why they lead to bearing failure! lack of grease then add in the articulation of the suspension the little bit of grease in just the bearings they will end up running dry. in no way should CV joints fail after only 12 track days.
this is the type of CV bearing packer we use at our shop.
this bearing packer fills the bearings completely and the concave area this takes just about 2/3's of the 14oz tub of grease to do both inner and outer bearing on one half shaft.
the grease is cheap and bearings with labor is expensive.
if your only putting just enough grease in the bearing and only the bearing than you may be able to get away with one tub for 4 CV's personally I in no way would recommend using that little grease .

 

[John H]

yes they were dry and not enough grease from the start.

If their joint was dry it was because your customer had an unaddressed leak. It doesn't matter how much you start with when it all leaks out...

in no way would I put as little grease as John stated this is why they lead to bearing failure!

If you want to overpack, you do you. But don't claim the correct amount is wrong and will lead to failure.

Manufacturers spec is under 100 grams, that tub is 400. Spec will fully pack the joint, which is already far more than necessary. It's kind of like a transmission, it doesn't actually have to be completely packed full to be fully lubed.

 

[RushR.Rentals]

no leaks at all !
yup I sure will use more that 100 grams and see if the CV's last for more than 12 event's but thanks for a pro such as yourself chiming in.
but as a pro you should know just because your told to put a certain amount of a product in doesn't always mean or be the correct amount.
looking at the other CV's they are all lacking lube ( not leaking ) and for 12 track days the little bit of lube there was shot.
one thing about developing a car you find things that may work better this is why things like torque specs change too. you know you may find say on a axle nut that the spec they 1st gave as spec could change.
transmission ?????? never seen one work like a CV joint !
how ever it's a common fact that in the MX5's transmissions you don't use the Mazda fluid you use the ford's trans fluid to have the cars shift smoother and better.

 

[jlaughman22]

I should be be receiving my rush in a couple of weeks, would this be something I should pull apart and check before putting it on the track ? Has anyone else run into this ?

 

[RushR.Rentals]

IMO yes ! add more grease that what's in the CV's stock from the factory.
you still have to check them on a regular bases.
there seams to be as John states around a 100 grams of grease per side this I pumped in 130 G's to each bearing.
because the grease on the outer CV is the one that had the grease or lack there of my thinking is that the cause is from heat build up from the brakes building heat transmitting the heat thru the hub and CV. this breaks down the outer CV grease faster than the inner CV. with this car the inner CV grease was also broken down and needed to be repacked but not near as bad as the outer CV's were.
values of things like lubrication that are used for a street car don't always apply to a race car. like in this case a street car at best may see speeds of say 100 MPH but not for lap after lap run session after run session like with a race car.


when it comes to all cars factory specs for how much grease they us in a CV joint there is not just one across the board set amount. depending on the auto manufacture you will find spec ratings from 80 to 150 grams used.
the thing with the auto markers spec amounts it's for street cars NOT race cars. when I worked for a factory VW rally team we would up the specs for the grease in the CV's from 90 grams to 120.
the hole reason to add more grease is as the bearing articulates running less grease as the bearing is spinning at a high speed the centrifugal force flings the grease out of the bearings. if more grease is used the centrifugal force can't fling the grease out as it's still immersed in grease as the CV joint articulates.

 

[John H]

you should know just because your told to put a certain amount of a product in doesn't always mean or be the correct amount.

As I said, <100 grams fully packs the joint, that is the basis for my statement. Pointing out spec is only in support of that. When you overpack a CV joint you're simply greasing your boots, and that grease doesn't return to the joint. I'm not going to continue to argue on the amount of grease as it's moot to the actual point.

no leaks at all !

If they came out dry they surely did leak. The biggest takeaway here should have been to remind everyone to monitor for grease sling and address, or suffer the same fate.

I tried to politely steer you toward that, but you continued in the direction of blaming the amount of grease, Obfuscation which is a disservice to the community.

Like I said, if you want to overpack them, you do you, but 30 more grams of grease doesn't solve the problem. No amount of grease saves a leaking joint.

 

[RushR.Rentals]

no you shouldn't be arguing ! John if you bothered to read the 2nd reply I stated after seeing this we will be inspecting our CV's on a regular bases. I'm not going to tell people to do it! if someone feels they should that's up to them.

packing the boots with extra grease ?????? who the hell is packing the boots with grease? I never said to do that nor does adding 30 more grams of grease do that all it does is fill the concave area in the photo shown. again common as it does fall with in many auto makers specs for street cars. giving no place for the grease in the CV as it goes thru it's articulation to fling off to because there is already a wall of the extra grease surrounding the grease in the CV.
it's pretty clear that there is not enough grease in the CV's . my thinking at 1st was the boot some how got pulled out and this is how the CV failed. but the CV boot was pushed out from the inside after the CV broke seeing the marks / damage on the inner edge of the CV boot.
there is no grease all over the back side of the wheel or all over the suspension showing no signs of a ripped boot and still driving the car.
the outer CV's were the worst ones having no grease to speak of in them with the inner CV's being slightly better but still pretty dry.
I'm feeling the cause is from heat getting transmitted from the brakes degrading and breaking down the little grease in the CV's from doing a proper job to keep them lubricated. so where is the little bit of grease going? it's getting cooked off and turning from a grease state to an oily state.

we will be leaving one of our cars CV's as they came from rush and the other car we will be packing the 30 grams more grease into the CV's we will like on every car we run take brake temps along with hub temps. after 6 days on track we will be pulling the axles out of both cars for inspection.
if they both pass the inspection we will put them back in the cars and do two more days and again inspect them. the CV2 grease is good up to 500 F degrees so if we see temps over the 500 F at any time we are taking temps we will have to find a remedy other than cleaning and repacking our cars CV's every few events.

 

[John H]

packing the boots with extra grease ?????? who the hell is packing the boots with grease?

Yea who does that.

 

[RushR.Rentals]

I guess when someone just wants to debate the uses of a little more grease that is still with in specs of so may auto makers its not even funny.
maybe it's the five more dollars in grease that's killing them?
maybe even after explaining over and over that they just are not getting it?
the vast amount of extra grease is filling the cup area in the splined shafts not the CV boot.
the cup area in the splined shaft to a limited extent will pickup a touch of extra grease as the half shaft articulates.

 

[RushR.Rentals]

this is the outer splined shaft from the left side that did not fail yet just as it come out of the car.
IMO it's dry very dry with next to no grease at all to lubricate anything.
All the boots are not leaking and the boots are still in good soft pliable condition.

anyone that has worked in the automotive industry as a tech and has seen a CV boot that has failed would in most all cases see CV joint grease all over the inside of the wheel all over the control arm, fender liner and other components.