Carrera CV Boot Replacement

[88-diamondblue]

Skidder, I didn't notice that on mine so I don't know if it makes a difference. Maybe Grady will have some insight on this one.

Mark, I had around 92,000 on mine. The mechanic said these are pretty tough and if there is not pitting or noticeable grooving they should be fine. I have a trip to the track and home (450 miles) and an after noon at the track and all has been good. No strange noises.

[colinsco]

This thread has been a great source of guidance and comfort as I replace the Lobro axles on my '88 Carrera but I would appreciate some confirmation on the torque specs for the axle nut. I see a reference to 330 foot/pounds in this thread but cannot find this anywhere else on the forums. Until the Bentley book arrives I am limited to Waynes book (second purchase after the car!) and the Haynes book that came with the car from a PO and neither give the spec. Tonight my son and I installed the new axles and torqued the inboard bolts (yes, 60 lbs) and replaced the shocks. Tomorrow we plan to do the final torque on those nasty axle nuts and end a winter drought and get our 911 fix. Can anyone please confirm the torque for the 32mm outer axle nut? Many thanks!

[Jascha]

The self-locking nut tighten to 460 Nm (~340ft-lb)

[dfink]

The general consenus has been a fat man on a 2 foot breaker bar. A skinny guy should invite over a fat friend to have a beer while standing on 2 foot breaker bar. They are correct on the 330-340 range. I bet at that torque there is a bit of a deviation. Get it as tight as you can then take it to a truck repair place and see if they would torque it for you. Takes a 4' long 3/4" torque wrench. I only need a 1-1/2 foot breaker bar I fit in the fat man catagory.

[Grady Clay]

Skidder,

Welcome to The Forum.
That is a new one on me. I’ll find out.


Guys, the torque on the axle nut sets the pre-load on the rear axle bearing. It is critical for that double-row ball bearing to be set correctly. If too low torque, the balls can loose contact and become damaged when re-connecting. Too high torque could overload the bearing (or break the threads I suppose).

I gave an explanation here: ”Rolling Drivetrain Noise“

For the record the torque specs for the axle nuts are:
M20x1.5 Castle nut with cotter pin – 300-320 Nm (221-236 ft-lbs).
M22x1.5 Self locking nut – 460 Nm (339 ft-lbs).

Note that the smaller rear axle bearing (’69-’73) has the same torque spec as the later, larger 80 mm OD (’74->) bearing.

If I were assembling a rear axle assembly from spare parts, I would use the larger thread stub axle and the higher torque spec if possible. The larger bearing is the most important reason for using the aluminum trailing arms on a ’69-’73 911.


There has always been discussion about clamps. Some prefer screw clamps but it is difficult to get to the screw with 100 mm 6-bolt CV joints. Some just use zip-ties. It is so easy to get the inexpensive clamp tool and use the Porsche Factory (Lobro) clamps, I don’t see any reason to use any other.

Best,
Grady

[rusnak]

I thought I'd revive this thread so that I could get some things answered.

I'm also posting pictures of brand new out of the box cv joints, to help someone else who is at the point of having to re-assemble his.

(1) I have read a lot of opinions on not clamping the inner boot end (small end) at the tranny side. The thinking is that the boot won't likely leak grease and by not clamping the small end, you might prevent the boot from tearing when you lift the car for service. Anyone else heard about this, and what are your thoughts?

(2) I still have no idea which end of the cv joint faces the boot, and which end faces the flange. I thought I'd toss the dice and make the side with the notch around the outside face of the outer cage the side that faces the flange. I'm embarrased to say that this is based on the little picture on the box, although if anyone ever mentions this, I'd try to deny it later.

See photos:

I was going to make this side face the axle boot (washer end):


and this end face either the wheel or tranny flange (circlip end):


Can anyone verify, or correct this? I can't seem to find my copy of Wayne's book for reference.

[Jascha]

I assume you are installing these on an '84 or earlier p-car...

If I understand your picture description correctly it may not matter.... some advocate switching them around when replacing the boots to equalize the wear pattern

[88-diamondblue]

Rusnak,

You are right in the way you they go on. I tried both ways and the circlip will only fit one way. Here is a shot before the grease.

[rusnak]

Michael:

You may have the inner cv cage reversed. I don't know if that matters though.

I thought people who switched them around to even out wear turned the whole thing around (axles and cv joints), thus maintaining the way the cv joints go on to the axle. Again, I don't know if this matters either.

[88-diamondblue]

In this picture it was a solid axle. LOL! The cage was on wrong as you pointed out. Didn't know you could put them on wrong but found out that you could.

[randywebb]

OK, I've already had a question about this - a Pcar mechanic told me that you had to put each of the little balls back into the same place on the cage that it came out of -- that they "wear into each other."

The idea was that over time they mesh together and if switched later on they would not fit well together and would make noise or possibly even seize up. I have since learned not to trust that particular mechanic for other reasons.

Anybody know for sure?

[rusnak]

The Bentley Manual states that you must put each ball back into the slot in the cage that it came out of. It goes on to explain that each ball is matched at the time of manufacture with the correct slot.

I was curious about this, so I measured the balls and found no difference from one ball to the other. The Bentley Manual also says you should not completely disassemble the cv joint. But what do you do when the boot tears and lets in dirt? You have to clean out all of the old grease, and to do that you have to take the cv joint apart. What I did notice was very substantial divots in the inner cage ears, and that the amount of wear was not consistent from one slot to the next.

I was bothered enough about the whole thing, and noticing some minor scuffing on the outer cage, I changed all 4 boots and all 4 cv joints. After putting fresh grease into brand new, cleaned cv joints, I was very surprised to find that the car rolls much easier and even accelerates with more power than I ever remember. I even broke the back end loose and got sideways merging into traffic. I've never been able to do this since I put on the 9x16s.

So for me, the empirical evidence suggests that the CV joints are first of all very much affected by wear. I also noticed that the cv joints do not wear evenly in each slot, and on each ball. I think the best plan is to keep your cv joints clean and well greased. If any dirt gets in, or any wear is noticeable, you have to change that joint. This means that the likelyhood that anyone will be disassebling the cv joint for any reason is low, or that they will do so at or near the end of the service life of such joint. If this turns out to be true, it is a tough and very hard fact of cv joint service. I would be happy to be wrong.

[fly4val]

A semi personal question for Grady,

Did you own or operate a VW/Porsche shop in Denver on the east
side of Broadway south of 6th avenue...also did you have a VW bug
with 'Turbo' personal plate in the mid 70's?

Does this sound like someone you know or knew if it is not you?

[hcoles]

did we confirm by experience that the balls need to go back in the same groves? This is a lot to keep track of if not necessary.

[RWebb]

Did it say they were matched by size? It doesn't seem like they would be matched by weight, but that might be possible.

Also, maybe the difference in sizes was smaller than the tolerance of your measuring instrument (?)

I would definitely try to replace balls back into the same position if they are used (worn).

Maybe not, if a bunch of shop owners and race car builders chime in and say it has not been needed in their experience (with hundreds of cars)...

[Mitch Leland]

Am I correct that my 930 axles don't come apart the same way? I can't remove the axle by removing the rotor, I have to pull the axle shafts out from the inside. However my axle and CV joints remove fairly easy by undoing the inner and outer CV hubs.

When I reinstalled my axles there was a cauliflower gasket that was difficult to keep in place while getting the 10MM bolts started. Did I need this, or could I have used something like Grady was talking about? I wanted to remove the stub axles to check the bearings, but that looked like an ugly job so I passed on it.

[Gunter]

Originally Posted by hcoles

did we confirm by experience that the balls need to go back in the same groves? This is a lot to keep track of if not necessary.

A few clarifications:
If you ever visited a Kugellagermachinenfabrik you'd understand that balls for various ball bearings are NOT manufactured individually.
They get churned out by the thousands; all the same size with Nano tolerances.
That means they have no special place in a bearing.
Cleaning a CV joint while keeping track of which ball goes into a specific hole is virtually impossible and not necessary.
The balls don't really wear; the cages do.
It's fairly simple: If there is severe galling in the grooves, replace the whole thing; if there is just a little wear, clean, re-pack with Moly and run for another 50K miles.
I don't think you can switch the CV's on a Carrera half-shaft.
CV joints on an SC axle can be switched over for a fresh wear surface.
That means a straight across switch, not a reversal of the shaft-rotation.
I would not recommend to change the rotation on the axle shaft because it would change the torque that has been induced into it for a long time.

[88911coupe]

I'm having trouble getting the tin covers on the outboard end (side that goes into the wheel) to even budge. It also looks like, on my '88, that the lip that is pressed onto the CV joint has been further stepped down or reduced in diameter which seems to make it look like it can't be tapped off as described. I can' t really tell from the pics if the CV joints in this thread are identical to mine. Can someone confirm the tin covers can be tapped loose on the outboard end?
Thanks,

[hcoles]

I think I mounted in a vice and tapped with small hammer and plastic pipe or wood or something so that I wouldn't mess up the cap... I aligned with the bolts to get it started

[88-diamondblue]

Buck,

On the later CV's you can't take off the outside tin without destroying it. Here is a link to the thread I did on this.
CV joint