CV Joint Question

[997at]

Got my rear axles removed today so I can clean and inspect the CV joints and replace all 4 boots (one was torn which is what got this all started). While I was removing them I made the mistake of removing the one axle completely first, and then the outboard joint of the remaining axle. I couldn't then loosen the bolts on the remaining inboard CV as the axle would just spin even with the car in 1st gear. What allows the axle spin in the reverse direction when in 1st gear? To remove the bolts I had to reconnect two of the outboard bolts, set the parking brake, and then remove the two outboard bolts once the inner CV was disconnected. Pic below of the axles……..now comes the fun part.

[Porboynz]

Its the differential drive, driving around corners would be hard on tires without it. I bet you do a job like this again you will loosen all bolts before removing. Have you noticed its always the last bolt to undo that's the hardest? What are the odds? Or is it because its the hardest that its the last, like procrastination.

[T77911S]

i just did all 4 on my 930.
things you want to note:
the groove on the outside of the outer flange goes out
the inner race has a raised portion that goes to the inside (mine did).
the bearing cage has an inner side and an outer side. one side is larger, goes to the outside. (so I have been told)
I would not mix parts.
also mark (left inner, rt outer etc....)
I flipped my CV's so they would wear on the other side, just as an test to see if they wear out faster or last longer. (I had one bad CV anyway but left it on)
I liked the swepco 101 grease. seemed a bit more tacky which I liked.

make sure bolt threads are clean when you put them back on.
new washers. you can get a bag of 50 at Fastenal.
make sure there are 2-3 bolt threads that stick out past the flange on the tranny.
Fastenal also has bolts in 5mm lengths if you need new ones.

trust me on this one, you DO NOT want one coming off.
the hardest part but most important is getting the bolt holes clean so the bolts stay clean when you bolt them back up

[ClickClickBoom]

Well worth the 30 minutes or so to read:
Reconstructing Constant Velocity (CV) Joints

['76 911S 3.0]

Just replaced the CV joints on mine this weekend...not a clean process. Pretty straightforward job as long as you have some good snap ring pliers.

[T77911S]

OH YEA!!
what a freaking mess.
I would love to see how someone like JW does it.
I did all 4 at once.
laid them out in their groups then greased and assembled them all at once.
then went back and cleaned them up.
I used brake clean on towels and air to clean the bolt holes.
then I cleaned all the bolts.

[ClickClickBoom]

I install mine dry, using Nordlock NLX locking washers, after wiping all mating surfaces with acetone. When the axle assemblies are in place and torqued properly, I measure 40 grams of CV grease into a small grease gun and inject it with a probe type fitting. I can feel each ball and recess and distribute the grease evenly around the joints.
After having a CV come loose and fall off, I decided a new process could be more effective. The dry assembly and Nordlocks insure that the highly stressed 100MM CV is as tight as the original design intended. The Nordlocks are designed to be installed with lube, on the washers and bolt threads, as per the product engineer. I can do an axle in about an hour, including solvent tank work.
Don't forget about fastener settlement, per the engineer, about 3600 seconds is the amount of time that full settlement occurs. Its a pain to leave everything apart while waiting, but fastener settlement is probably the primary reason for CV joint assembly failure, followed by contaminated mating face assembly.
My car is my daily driver and as such reliability is paramount, the CV reconstruction thread is pretty much the bible for axle work, the Grady Clay input is legendary!

http://www.windpowerengineering.com/design/mechanical/fastening_joining/counteracting-vibration-and-settlement-in-bolted-joints/

[mike635]

I replaced my axles earlier this summer. A trick I learned from someone on this board (wish I could find the original thread) to help with re-installation is to get a spare bolt and cut the head off, then saw a slot in the end. When installing your axles, you put this bolt (you can use two) in the flange and use it as a guide pin to hold the assembly in place while you install the bolts. Once you've got the axle held in with a couple of bolts, you remove the headless bolt using a flat blade screwdriver.

I can't imagine how you'd install a complete axle assembly by yourself without using this trick/tool but I'm sure plenty of people with more mechanical dexterity than me have done it!

I can post a pic of the bolt/tool I made if anyone is interested.

[997at]

Thanks for all of the tips guys………..going to use them all. I haven't done the disassembly yet, but I find it odd that there are no gaskets or washers anywhere on my flanges or bolts. Normal?

[mike635]

Not sure what year car you have but my '81 SC didn't have any washers or "moon" plates. If you read the long thread referenced above, you'll learn a lot about the fastening hardware associated with the axles, lots of good stuff. I went with new "moon" plates and Nordlock washers when putting things back together. Might be overkill but cheap insurance!

[Walt Fricke]

Worrying about cleaning CV bolt holes and flange threaded holes has to be a kind of automotive DIY urban legend. Consider torque in an even more critical application - rod bolts. The normal specification for use of a number of the super strength rod bolts out there, like ARP, is to lubricate the threads! Why anyone worries that some grease on the threads of a CV bolt which is properly torqued is going to allow it to back out is just beyond me.

The whole purpose of torqueing bolts is to cause them to stretch. As long as you don't stress the bolt beyond its elastic limit, that stretch is what keeps the flanges or joints fastened tightly together, and it is the friction produced by the clamping between the clamped surfaces which prevents the two sides of a rotating joint rotating precisely together, with no working back and forth. Working back and forth can induce a rotation on a bolt, and it is not the shear strength of the bolts which makes a joint work - it is the clamping force. Or so my engineer friends tell me. Much easier to keep the two clamping surfaces clean and dry than to fuss with the bolts. And the specified torque is an indirect way of approximating the amount of stretch needed for the required clamping force. A lubed thread is going to achieve that stretch more accurately, because friction on the threads will cause torque readings to be higher than what may be needed to stretch the bolt properly. Porsche obviously does not consider CV bolts to be quite such a critical application, as it gives no special instructions on how to torque them. Some fasteners come with one torque for lubricated threads, and another, higher, one for unlubricated threads. Where a stretch gauge is not used (easy to use on rod bolts, would be pretty tricky for CVs), ARP gives a spec for some repetitive torqueing and unscrewing and repeat to burnish the threads so the measured torque will produce the required clamping force.

While one often sees advice that these parts should not be mixed, we are a long way from the days of the Brown Bess so lovingly hand assembled and fitted by the British Army's armory. These are precision parts, and are not honed together. One ball is like any other ball, and it doesn't matter which ball goes in which slots, or where in the intermediate steel cage. I've assembled a CV from saved parts of different CVs which weren't pitted in their races and passed the finger nail test as to the wear area (not grooved)and it has given as good service as a brand new one, at least in a racing application.

I do like the idea of using the hypodermic type needle on the grease gun to reduce the messiness of reassembly. But forcing the grease in has tended to make the needle pop off the end of the grease gun and create other problems. Maybe I just need a better quality one. The best boot for doing this would be the ones which are held onto their boot flange with a metal band. If you remove this you can slide the boot off after the axle is reinstalled, and grease away, then reinstall the boot and use a hose clamp, or even tie wraps, to hold the boot in place.

Fastener settlement is an interesting concept, and not one Carroll Smith addressed. If retorquing these bolts after you have the car sitting (perhaps doing other useful tasks the while) is the equivalent of retorquing after some amount of driving, that would be good. However, I've replaced four broken axles at race tracks, and it is torque them up and get back on the track. Haven't had one of those loosen.

[T77911S]

Originally Posted by mike635

I replaced my axles earlier this summer. A trick I learned from someone on this board (wish I could find the original thread) to help with re-installation is to get a spare bolt and cut the head off, then saw a slot in the end. When installing your axles, you put this bolt (you can use two) in the flange and use it as a guide pin to hold the assembly in place while you install the bolts. Once you've got the axle held in with a couple of bolts, you remove the headless bolt using a flat blade screwdriver.

I can't imagine how you'd install a complete axle assembly by yourself without using this trick/tool but I'm sure plenty of people with more mechanical dexterity than me have done it!

I can post a pic of the bolt/tool I made if anyone is interested.

its not hard
do the trailing arm side first.
put one of the flange holes at 12 oclock, then put a wrench on one bolt at line it up at 12 oclock.
same for the tranny side

good idea you have though.

[T77911S]

walt, I have had 2 come off.
one was my 914 YEARS ago and one was my 77s. the 914 came off at about 10mph but the 911 was a bit fast and made quite the racket and put a few dents in things.
I did not learn the first time to clean the grease from the threads.
now I drive the car then recheck after 100 miles or so.
with the 77 being the second time this happened I took more notice as to why it was happening.
I noticed the bolts where coming lose and It took a while to get them to where they were not loosening up.
this is when I looked into the proper bolt length and cleaning the threads better.

proper bolt length
clean threads
new washers
proper torque
rechecking them

[ClickClickBoom]

Originally Posted by Walt Fricke

I do like the idea of using the hypodermic type needle on the grease gun to reduce the messiness of reassembly. But forcing the grease in has tended to make the needle pop off the end of the grease gun and create other problems. Maybe I just need a better quality one. The best boot for doing this would be the ones which are held onto their boot flange with a metal band. If you remove this you can slide the boot off after the axle is reinstalled, and grease away, then reinstall the boot and use a hose clamp, or even tie wraps, to hold the boot in place.

Fastener settlement is an interesting concept, and not one Carroll Smith addressed. If retorquing these bolts after you have the car sitting (perhaps doing other useful tasks the while) is the equivalent of retorquing after some amount of driving, that would be good. However, I've replaced four broken axles at race tracks, and it is torque them up and get back on the track. Haven't had one of those loosen.

Agreed,
My grease inserter sn't a hypodermic, it's about the diameter of a pencil and squirts a 3mm or so diameter grease flow. 40 grams of grease takes about 5 minutes to apply, due to the repositioning of the applicator.
Fastener settlement is a real issue for the Nordlock engineer, he harped and carried on for about 1/2 of our conversation. The majority of his concerns came from dissimilar materials hardness, i.e. hard bolt, soft surface, if the surface is soft enough to deform, the time for complete settlement can approach 3600 seconds with steel. My first torquing on a new dust boot was to 30 ft lbs with a greased thread and washer, the second torquing(static, no driving) 10 hours later at 30 ft lbs yielded about 1/8th of a turn of the fastener.
My bet is for a previously compressed materials stack up the time will vary due to changed compression of the original material. The whole "drive a hundred miles and retorque" is really a indirect solution to the issue of settlement.