Constant Velocity (CV) Joints
The following topics are addressed in this article -
- From the Manuals
- CV Joint Servicing Procedure
- Boot Repair
- Questions and Answers
- Also, see Sean Bartnik's excellent CV Joint Maintenance article, with lots of very helpful pictures.
From the Manuals
From the Bentley Manual -
The double-jointed rear axle with constant velocity (CV) joints was introduced on Type 1 cars with manual transmissions in 1969. There are four CV joints -- one on either end of the two axles.
The CV joint looks very nice in this picture, but packing it
with molybdenum grease is a very messy job.
- Photo courtesy of California Import Parts, Ltd.
The Haynes Manual gives the following advice (paraphrased), followed by directions for overhaul of the CV joints and replacement of the boot -
Remove the driveaxles.
Note: Paint or scribe across components so they can be reinstalled in the same relationship.
Inspect the CV joint dust boots for cracks and tears. If the boots are in good condition, the CV joints are probably clean and adequately lubricated. But if either boot is cracked, torn or leaking, remove it, clean, inspect and rekpack the CV joint and install a new boot. If the balls, splines or races are damaged, corroded, worn or cracked, replace the entire CV joint. Pack the bearing assembly with CV joint grease.
CV Joint Servicing Procedure
Rob has provided the following procedure for servicing the CV joints -
Note: Regreasing of the axles and constant velocity joints is not difficult, but it is a VERY messy job, so have plenty of rags or paper towels, and if you prefer to keep your hands semi-clean, latex gloves.
- Do one side at a time from start to finish (there’s a reason for this). Remove the hub cap and the split pin from the 36mm nut holding the brake drum. Loosen the 36mm nut, THEN jack the wheel off the ground. Support it on a jack stand (don’t trust just the jack).
- Remove the brake drum.
- Now you have the wheel off for easy access, crawl under the car where you’ll see the two constant velocity joints on each drive shaft, each held in place by six bolts. Occasionally these will have an Allen Key hex head, but they usually have have a 12-point star socket head. This needs an 8mm 12 point spline drive tool to remove it.
Note: Make sure you use the correct driver – you need a good connection to re-torque these when you’ve finished.
You may need to get an 8mm 12-point spline drive socket from a VW shop if you car has these (most other automotive shops carry
them as well).
- Under the bolts is a serrated lock washer and a set of three “paired” plates, one each for 2 bolts (three plates for six bolts).
- Remove the six bolts from each end of the CV drive shaft. The drive shaft will then come free very easily, and each exposed end of the CV joints is full of black grease which, if old enough, can be quite runny, so be warned!
- Lay the shaft down for the moment and clean off all grease inside the dished CV attachment plate in both the gearbox and the stub axle (you‘ll be repacking these dished areas with fresh grease later).
- The CV joints are held on the drive shaft by a circlip – you’ll have to wipe the grease from the end of the shaft to see it. Moly EP grease is black, and REALLY sticky, so if you find the grease looks more brown and watery, then it’s way overdue for a change.
- There is also a rubber boot on the inner (axle) side. On some cars these are held with one-shot hose clamps to the aluminium CV cover; on some cars there is a better design with the cover having a raised retaining ring and the rubber boot just fits over this ring. On the small end of the rubber boot, a hose clamp fixes the boot to the shaft. With both ends of the boot free, you can slide it away from the CV joint.
- With the rubber boot freed, you can gently tap the aluminium cover plate off the joint and down the drive shaft. Then with the circlip removed, the CV joint can be driven off the shaft – it’s a light interference fit. Open the jaws of a vice so the shaft fits between, and the jaws supports the inner CV race. Tap the axle downwards until it falls on your foot! This eye-watering experience will remind you to keep your foot out of the way and put a wad of rags or similar there to catch the shaft next time.
- The CV joint will come apart, but you can leave it assembled and wash it in solvent (mineral spirits, kerosene or gasoline will work, but gasoline is dangerous, so I can’t recommend it) and a toothbrush – getting rid of all traces of old grease (several fresh batches of solvent may be needed).
- Now inspect the joint. If the balls and races are shiny and bright, you can reuse the joint. If the balls are “blued” or there is any scoring of balls or races, the joint is worn. You can still reuse it if you like, but start saving for a replacement – it might last a thousand miles or 10 thousand miles. New joints are over $50 US each (2002 dollars) so regreasing them about every 5 years (depending on use) can save you a lot of money.
- If you do need to disassemble the joint, you can turn the inner race about 30 degrees to the outer race and the two will pop apart with hard finger pressure. Remember me saying at the start to do only one axle/CV joint at a time? The reason is that the balls are matched to the joint, so you do NOT want to play mix-n-match. Doing just one joint at a time ensures that the right balls go in the right joint.
- Clean old grease out of the rubber boot and the aluminium cover plate too – this will be almost completely refilled with new grease as a reservoir.
- Once the joint is completely clean, place it in the (clean) palm of your hand, and start pushing Moly grease into the balls and races with your other hand until it works out the other side into your hand.
Note: The CV joints are lubricated with black Moly grease (the pack usually says “contains 3% Molybdenum Disulphide”) – and is sometimes called Extreme Pressure (EP) grease – Castrol LMM or similar. This grease works well with the rocking motion of the CV joint when in use - the balls dont spin at all but move backwards and forwards in their races (grooves). All the engine torque is transferred through those balls, hence the need for a special grease to resist that pressure between ball and race.
- Place the CV joint back on to the axle and push it down so you can replace the circlip (compress this clip first to get a firm grip if needed). Now work as much grease as you can into the drive shaft side of the joint, and bring the aluminium cover plate up to the inner side and make sure its as full of grease as you can get it before pushing it back on to the outer race – if some grease squeezes out the inner part of the cover (the drive shaft hole) then you’ve done a good job. Pack more grease under the rubber boot and bring it up to the cover. Fit the hose clamp(s) as required.
- Do the CV joint at the other end of the drive shaft.
- Before reattaching the drive shaft to the gearbox and stub axle, fill the recesses in the attachment flanges with grease so you have a reservoir on that side of the joint, but wipe the outer circle (where the bolt holes are) clean. Add a mound of grease to the exposed side of the joint too, but clean the rim where the bolt holes are. The idea is to create a reservoir or grease on each side of the joint so it never runs out of grease.
- Bring the CV joint up to the flange and reinsert the bolts - you did clean these bolts too didn’t you? We don’t want ANY dirt getting in to the expensive CV joint!
- Make sure each bolt has it’s twinned (two bolt) plate, and the ridged lock washer.
- Tighten the bolts to 25 ft-lbs. You may have to push the rubber boot away with your thumb to get the tool on to the bolt, and rotate the joint for easier access as you go. The four CV joints should use about a pound (1/2 kilo) of grease (a full tube of grease-gun grease). Don’t skimp on this – those joints work hard, and careful attention to cleanliness and lots of new grease will ensure a long life for them.
- Once you’ve finished with one side of the car, do the other – remember, it’s therapeutic for both you and the car. :-)
There you have it – “as new” CV joints which will last you many thousands of miles. After you have driven a few miles, check the CV joint bolts – I found two of the 24 bolts were not torqued properly – whether I’d missed the final tightening, or they had worked loose I don’t know, but it’s a good check, the last thing you need is a drive shaft coming loose at 60mph and flailing everywhere.
Someone wrote with a boot repair procedure he learned while at Auto Zone. (We haven't tried this so we can't vouch for it, but it looks good.) -
- Clean the CV boots with rubbing alcohol and paper towels.
- Apply black RTV sealant to the cracks.
- Let the sealant dry for 24 hours.
- Spray the boots with WD-40 after 24 hours and twice a year or every 6,000 miles thereafter to help keep them from cracking.
- Check for more cracks occasionally.
Don't use Armoral or similar products on the boots because that makes them crack.
Questions and Answers
Question - I started to hear/feel a moaning sound that seemed to come from the left rear. Was almost indescernable at first but is louder now. If you turn the steering wheel slightly left, it goes away - slightly right - it gets louder. It's accompanied by a high frequency vibe - feels like putting your hand on a running electrical device. Have I got a LR wheel bearing going bad? CV joint?
Rob responded - Very possible it's the wheel bearings - the CV joint is more likely to have a constant noise I think. You said your car had the IRS suspension, so it has greased rear wheel bearings and CV joints. The CV bearings are grease filled, and it is possible that they haven't been repacked in so long they've gone dry.
The wheel bearings are also greae filled. The outer bearing is a roller bearing, and the inner one is a ball bearing, which takes most of the side load when turning.
I haven't had to remove the CV joints on my '68 Bug yet, so my direct knowledge of the disassembly is sketchy, but I know that the inner (ball) race needs a tube of the right dia to use as a drift to tap the outer race out of the housing (towards the centreline of the car) from the outer side of the car. It's held in place with a large circlip. There are tube spacers between the two bearings. When removing the pieces, take careful note of which way they are mounted, as several components must go back with the same orientation they came out.
If you need more direct info, I have contact with a group here in Australia who advised another Aussie on this procedure for his car - I can't find the article again (we had to change the newsgroup server and I think it's on the old one), but I could certainly get the info again.
Use lithium based wheel bearing grease - Castrol LM or similar for wheel bearings, and Extreme Pressure Moly grease - Castrol LMM or similar - for the CV joints. Wheel bearing SPIN so need a grease appropriate for that. CV joints ROCK, and EP grease is best for that.
Question - When I took the drive shafts off the inner CV caps stay on the transaxle (they have captive nuts in them for the socket head screws). I couldn't see any way to get them off; on all pictures of the transaxle I've seen they aren't there. And they interfere with the two tranny support channels that run down either side -- you have to pull the tranny back far enough to clear them. I sealed the CV joints themselves in plastic bags -- do you think it would be wise to repack them just as a matter of course?
Rob responded - I'm not going to be much help here I'm afraid I have the swing axle and am not familiar enough with the IRS axle to comment. I guess if it's possible to repack them, it certainly won't hurt.
Question - I am concerned about the CV joints -- the thought of repacking them doesn't exactly thrill me, but I suppose I really should do it before I reattach the drive shafts to the transaxle. I dunno. My test showed them to be good -- maybe I could just stuff some more grease in there and bolt them up.
Rob responded - If they were OK, I'd bet they'll be OK for a long time to come -- if you can get a bit more grease into them easily, then go that way, but don't worry too much. They don't 'work' like a spinning bearing anyway -- just 'oscillate' slightly in use when the suspension works up and down.
Rob wrote - Yesterday on the way to work I thought I was hearing a slight grumble from the left-rear of the bug. On the way home it was louder, and I was thinking "dry wheel bearing or slightly loose wheel bolts". It wasn't wheel bolts (easy to check) so last night I stated pulling things apart at the left rear wheel. I found all six socket-head bolts which hold the outer CV joint to the stub axle were loose - the obvious source of the grumble, and very strange since I've driven this car 13000 miles since I bought it, so why would they suddenly come loose, and only those 6 - the other three sets were fine.
While I was there I decided to look at the CV joints and wheel bearings anyway. Good thing I did. Can you say "35 year old grease"? The outer roller wheel bearing was almost dry and surrounded with dried grease. The inner ball bearing was better greased, but not much there either. The spacer tube in the middle was still covered with good grease (the space between the bearings is fully packed with grease).
Anyway, I didn't have enough time to completely remove the inner ball bearing (it's knocked out using a drift from the other side of the axle assembly) but the bearing cage and inner race for the outer bearing fall out easily, so that got a complete wash and re-pack, and the ball race got grease pushed through the balls as much as I could with a finger from the inside. Castrol LM (lithium) bearing grease. The CV joint had some grease on it but not really enough, but since I didn't have time in one evening to remove the complete shaft and the CV joints themselves (CV at both ends) I just repacked it with extra Moly grease (Castrol LMM - extreme pressure with Molybdenum Disulfide added). No noise from that area this morning, though I can still hear a tiny grumble from the back, which means the right side is in need too. So this weekend will be spent working on the other CV joints and right side wheel bearings.
It's interesting in one way - as I drive the car I think to myself "what jobs should I do on it" and the thought "grease rear bearings and CV joints" was very high in my thoughts. It seemed to me to be a place that would be easily forgotten, and unlike the swing axle models, (which have the gearbox oil providing lubrication for the wheel bearings), they NEED attention every 30,000 miles or so - all hard working components. And if greased regularly, they will last almost for ever.
The bearings and CVs sure are a messy jobs - especially the Moly grease - its black and VERY sticky. Even after 3 good hand scrubs I still have traces on my hands this morning.
Next time I'll remember to wear latex gloves!
Dave wrote - The CV bolts on our '73 SB car aren't allen-head -- they have kind of a star-shaped hole in them -- I had to buy a special little fitting. Rob adds: - yes, the 12 point spline drive socket. I've seen allen head bolts too, but the 12 point socket head seems to be the VW original.
There are two lengths to these bolts - Muir mentions the "newer 1mm shorter" replacement type and so does Bentley, so I'm guessing that the older type had a touch of interference (the bolt pokes out through the hole a little) - and they made them a little shorter and changed the head at the same time. The "new" short ones fit in the older cars no problem according to Muir.
Question - There's a set of six bolts on both ends of the axle, four sets altogether. I only disconnected the one's on the tranny end when I did the tranny job.
Rob responded - Yes - that's right, you can remove one end or the other as needed. Removing all 6 on each end makes the job easier though - the axle with CV joints attached just drops out of the car so it becomes a bench job rather than an under-car job.
Interesting thing here - I looked at Bentley, Muir and the Aussie book I have - all have a pic of the exploded CV joint and drive shaft, and all have SOME description of the stub axle/bearings, but none of them have a good pic of it. It took some careful reading to make sure I wasn't doing anything wrong (Bertie's swing axles are different, so it' my first encounter with the CV joint/axle on an IRS bug.) Not especially hard, but different.
Regarding Rob's comment - ... just remove both sets and the drive shaft with CVs drops out.
Dave wrote - Yes! Drops out and scatters ball bearings all over the place! I wrapped plastic bags around our CV joints while the tranny was out …
Rob responded - I didn't let it get that far :-) - you have to twist the CV sideways about 30 degrees for that to happen. I didn't disassemble the CV joints - took the easy way out of washing the old grease out with kerosine and a tooth brush, and then squeezed new grease in from the outer end till it was oozing through the other side. Probably not as good as a complete disassemble, but the other end (which I did a couple of months ago the same way) still looked well greased, so I think it should be OK. I'll wrap plastic bags around my CV joints when I take them right off this weekend too.
Question from Dave - I hope I didn't do something wrong? When I took the tranny out I had a hard time keeping the inner CV joints in one piece -- I had to tie them up with plastic bags to keep the ball bearings from falling out. I'm not getting any weird noises from back there, so I hope its all okay.
I did pack some grease into them in place -- a very poor repacking job. I should have done the job right while I was there, but I was tired of the whole thing and wanted to get it over with!!
Rob responded - So long as you aren't hearing grumbles I'm sure they would be fine for a while. I checked out the other end of the one I was doing whilst I had the shaft out (I only had to do the fourth one since I'd got to the first 3 some months ago) and it had plenty of grease in between the balls etc, yet I did a quick-as job on them too. So the grease tends to hang in there OK.
Rob wrote - My '68 Bug had a puddle of oil under him yesterday, but hasn't leaked since - very strange. I also have a slight grumble from the left rear wheel area - the bearings have been regreased recently so I'm wondering if it's a loose CV joint or something like that.
I looked under the car before driving home yesterday, then crawled under there with the 12 point spline drive to tighten up a VERY loose inner CV joint on the left side!
That got me home and on the drive I thought about the oil leak problem. When I regreased the CV joints a few months ago that one had very runny looking old grease (more so than the other CVs) and I think I must have a pin-hole in the gearbox flange there which is letting gearbox oil into the CV joint. As the joint loosened it release the oil I saw as a puddle under the car (about a cup full). And then it didn't leak again as it had "emptied" the CV joint and rubber seal.
I checked further last night and found the right inner CV slightly loose too - not as bad as the left though, and no indication of oil in the joint.
On the way to work this morning I could still hear a slight grumble - might be either insufficient grease/oil in the left CV, or might be low oil in the gearbox (though only a cup full escaped through the CV so I don't think so.
That means I'll have to remove the CV tonight and check it out.
It's got me puzzled as to how the gearbox oil is getting into that joint though - the drive shaft comes out of the gearbox and has a large flange to attach the CV to. The flange looks solid, but I suppose if the shaft in the gearbox is hollow and there is a pin-hole through the flange, then gearbox oil could slowly leak into the CV. I am not really worried if that CV joint has to run on gearbox oil instead of grease - the swing axles use gearbox oil for the wheel bearings so that oil obviously works OK, but if it's going to come loose and leak the oil out then I have a bigger problem - a dry CV and a gearbox low on oil.
I took the offending CV off last night, and yes, it had more gearbox oil in it, so there is definitely a leak from the gearbox into that CV and boot. It looks like the flange is pressed on to the shaft into the gearbox, and I couldn't see any crack or hole, but it has to be there!
I repacked the CV with grease, even though I know it will eventually get flooded with oil again, and the rumble is still there so now I don't know if it's the CV or the gearbox (maybe a loose flange even!)
The Bentley Manual has no picture of the area but talked about "removing the plastic cap and then the circlip and pulling off the gearbox flange," and then I found an exploded diagram in the Aussie manual which showed the cap and clip. So it looks like the centre of the flange has a plastic sealing cap (which must be leaking), and a wire clip which holds it on to the shaft inside the gearbox (splined).
The one in there now must be steel grey as it doesn't look like a cap - looks like the end of an axle. Anyway - both books say the cap must be pieced and levered off to get it out, so I stopped at the VW shop and bought one (a black one this time). He thought he didn't have a clip (I want one just in case the one in there is broken) but it turns out it's the same sized wire clip which holds the CV joints to the axle, so I have one of those now too. So with a cost of $6 I MIGHT have the problem fixed.
So guess what I'm doing on the weekend. The "oiled" CV is still grumbling so I don't know how it will go once I get the new seal cap into the flange and regrease the CV - I hope I don't have to replace it as it's $110 from the VW place (advertised for about $55 in the USA). I MIGHT be able to get one from a bearing company - they are aparently a "standard" industrial sized CV, so Timken or SKF might make one.
I got to the bottom of it yesterday. At some previous time, a PO has dug out the seal (damaging it) and put the same one back, covering it in grey coloured sealing mastic so it was almost impossible to see it as a seal even when the Moly grease had been wiped out of the flange; and not knowing how the assembly was made, I didn't realise I was looking at a disguised seal at first.
Anyway, the mastic had apparently softened, allowing oil in through the damaged seal (you have to DIG them out and replace them with a new one). The clip which holds the flange to the gearbox shaft (under the seal) was OK, so I was able to replace the seal with a new one. The CV looked OK - shiny in all the right places, so I've repacked it, but have reversed the axle so both CVs are now driving in the opposite direction - just to change the load point in case there is some minor damage (new CVs are about $110 here!)
Whilst under there I found that the left rear brake drum was not as tight as it should be on the axle - a tiny amount of movement, which might have been part of the rumble, so that got retightened (first time in my life I've ever had a loose brake drum - I'm very careful with the 36mm nut and pin). so I'll see how it drives today - hopefully all fixed.
Regarding the bolts that hold the CV joints in place, Rob and Dave initially decided that there are three types - allen key, 6-point, and the more common 12-point. There is apparently a 12-point tool which is part of a 1/2 socket, so you can use a normal ratchet or torsion bar to tighten them. Robs comment : yes, it's called an 8mm 12 point spline drive - it has a built on socket so it fite a standard 1/2 square drive bar. YThey come in 2 lengths - a very short one and a longer one - about 2.5 inches (50mm). That one fits just right - long enough that the shaft clears the CV boots and the socket part does not interfere.
Dave wrote - I just looked at the tranny removal procedure, which I wrote, and it says -
Remove the 8mm twelve-point socket head screws from the transmission end of the driveshafts. (Caution: Use the proper twelve-point driver for this job -- do not use a hex-head drive, as it may ruin the screws.)
I found a wrench (spanner) that just fits the hexagonally-shaped arm, then I held the tool in place with the driver and turned it with the wrench. Works great, if you can keep all those pieces together long enough!
Rob responded - I discovered that only a few of the bolts are actually hex-head (allen key) - most are the correct 12-pointers when I dug the road crud out of them - surprised me to find that - I guess the previous owner found some hex head bolts to replace damaed originals.
So I had to find a 8mm 12-point spline drive (as they are called here), and all bolts are now 12-point. It was quite a job finding the spline drive too - the VW places didn't have any left (usually have some) and I had to ring up a number of specialty tool shops to find one. It sure made a difference tightening up the bolts with my 18 inch long torque wrench. With the correct spline drive socket and the torque wrench, it was very easy to ues.
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