Friday, December 1, 2006

VW - Boot Camp

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No, we're not at war, but we've definitely got a fight on our hands when it comes to CV joints. And since you only need to do your boots every 30,000 miles you're not likely to become proficient at it. So here's a little refresher course. But before we start, I want to preach a little pre-sermonette at you.

When you do periodic maintenance on CV joints you must insure the parts are not thrown out of balance. Before taking anything apart, make orientation marks that will allow you to reassemble the parts in exactly the same relationship as they were originally installed. That includes not only the CV joints to the stub axles and tranny, and the CV joints to the axles, but even the balls within the CV joints; they should go back into their same races and the same opening in the cage. John Muir failed to make this point in his otherwise excellent discourse on CV joints and that failure had expensive consequences for lots of VW owners who reassembled them in a willy-nilly fashion and even used hose clamps and the like when installing their boots. The axles rotate at about a thousand rpm at freeway speed. The imbalance created by the screw-type clamps causes premature failure of the rear wheel and differential bearings. As with pounding on the wheel nuts with a hammer & chisel, this is another instance where the earnest efforts of St. Muir did far more harm than good.

Back to Boots

The boots are those rubber bellows around your axles. Swing-arm trannys have two of them, one on each side. Later model 4-joint trannys use four of them, one on each end of each axle. (Both early and late VW's have independent rear suspension systems. The term 'IRS' as applied to late-model trannys was invented by magazine editors [who seldom get things right anyway].)

On early swing-axle trannys there is no periodic maintenance requirement for the boots, you simply check them now and then, replacing them if they become torn (as they all will) or leak excessively. On swing-axle trannys the axle runs in a housing; the boot flexes with the rear suspension but does not rotate, permitting the use of split-type boots as replacements. Since the boots serve only as an oil seal they should be replaced if they are no longer doing their job.

On late model 4-joint trannys the boots act as grease seals for the Constant Velocity (CV) joints and rotate with the axles. In order to lubricate the CV joints you must remove the boots. Because of the unbalanced nature of split-type boots they can not be used as replacements, you must dismantle the CV joint and press the axle out of the joint in order to slide the new boot onto the axle (and the old boot off).

Read St. Muir

John Muir's 'Idiot' book provides the best available step-by-step procedure for the removal, lubrication, and replacement of your CV joints. If you don't hold a copy of 'How to Keep Your Volkswagen Alive...' go buy one. Now. (I'll wait until you get back.) But you should also have the Haynes VW manual (#159) which is superior to all others thanks to its lavish use of illustrations. They do an especially good job describing CV joint maintenance.

Proper Parts and Tools

About three weeks ago you should have ordered your boot kits. A 'boot kit' consists of a replacement boot, eight (or four, depending on model year) new bolts, a new splined washer (needed to provide the proper pre-loading during reassembly), a new circlip, 90 grams of CV joint lubricant, and a new boot clamp. The best kits are from Meistersatz, the German company that supplies VW with your original boots.

If you've never done your boots, order four kits and do all of your CV's. It will provide you with a base-line for doing them in the future. You'll also need about twice as much lubricant than is supplied with the kits; pick it up locally. If some of your old boots are still in good shape, clean them and hold them as emergency spares. You will need to carry a spare tube of CV lube but you can make a nicely balanced emergency boot-clamp using wire. (The trick is to make two wrappings, 180 degrees apart, having the same number of twists so as to maintain proper balance. Use stainless steel aircraft-type safety wire if you can get it, stainless steel MIG wire if you can't, bailing wire as a last resort.)

Over the years Volkswagen used different numbers of bolts on their CV joints, and different sizes, too. The bolts are socket- head types using EITHER Allen-head sockets or the splined 12- point '3-squares' pattern (ie, three squares superimposed, each rotated 30 degrees from the other). Volkswagen has used both 6mm and 8mm sizes.

Since the Allen-head type may be used as replacements for the splined type, and since the splined type came in two sizes, and since some prior owner may have serviced one of the CV's but not the others, one of your first chores will be to determine what type of bolts are dealing with. Raise the vehicle, support on jack-stands, crawl under and scrub the heads of the CV joint bolts clean using a toothbrush and solvent. Be prepared to spend up to one hour on this job. You must clean the socket of every bolt and there are 24 of those puppies. If you fail to get the sockets clean the bit won't seat properly and you'll strip the socket, leaving you the lovely task of worrying the bolt loose using vise-grips. And don't assume all of the bolts are the same! Scrub them all; you may find one of your CV's wearing bolts different from the others.

Alas, Allen-head wrenches cannot be used on the 12-point splined bolts, nor visa-versa; you'll only ruin the bolt if you try. The majority of Volkswagen CV joints use the 12-point splined socket head bolts of the 8mm (socket-head) size. J. C. Whitney sells a four-piece set of such bits in 6, 8, 10 and 12mm for about $10 (p/n 14 xx 1662-P). Unfortunately, the bits are American-made, their shanks are 5/16" for the two smaller sizes, 1/2" for the larger (that is, the bits will fit sockets of those sizes). The 1/2" isn't a problem; you can use it in a 13mm socket, but the 5/16" size -- including the 8mm bit, the one most of us will use, is something of a poser since it's too large to fit an 8mm socket, too small for 9mm. I'm lucky to have a full set of metric and SAE sockets but if all of your tools are metric you will have to buy a cheap set of 3/8" drive SAE sockets in order to use the 8mm bit. The best solution is to find the bits already mounted in sockets (they come that way) but I don't know of a mail-order source. Indeed, my frequent citing of J.C.Whitney parts and tools is not from any admiration of their quality, service or price, but only due to their global availability.

(One word of caution: '3-square' pattern socket head bolts used on Volkswagens are not Torqx-bolts. Torqx is a 2-triangle pattern (ie, six points, rather than 12). The typical hardware store clerk doesn't know the difference, apparently defeated by an number greater than five. 3-square pattern socket-head bolts are found mostly on European vehicles, Torqx on American and Japanese. Brazilian vehicles use a pattern that is perfectly round :-)

As a personal note, I've made most of the Allen-head and splined tools I use by cutting off the bit and brazing it into a suitable socket, usually something picked up at a swap meet. Such bits are made of hardened steel, they will dull a file and strip the teeth from a hacksaw. The proper way to cut them is to use an abrasive cut-off wheel or a diamond saw. Cut-off wheels work best; the harder the material, the faster they cut.

The final tool you must have is an accurate torque wrench, and this is one of those cases where a clicker is superior to the torsion beam type. Working overhead, under the vehicle, it is very difficult to position yourself so as to read a beam-type torque wrench without introducing parallax, whereas the clicker can be read upside-down, behind your back and in the dark, if you wish.

Your Bentley manual fails to include the proper torque values for the two sizes of bolt used on the CV joints. Most of us have the 8mm bolt; they should be torqued to 25 ft/lbs, the 6mm to 31 ft/lbs. (That's right; 25 for the 8mm, 31 for the 6mm.) Run them up snug, then torque in a cross-pattern for the 6mm, a star for the 8mm (If you've got the 6mm bolts there should be only four of them.)

Hydraulics vs Hammers

The Bentley manual shows uniformed Volkswagen mechanics using the standard-issue Volkswagen hydraulic press to push the axle out of the CV joint (and pressing the CV back onto the axle when the job is done, no doubt marching in lock-step between times). St. Muir sez use hydraulics if you got'em but a hammer will work too. In this case, I agree with him.

The Haynes manual shows the mechanic pushing the axle out of the CV joint with his thumbs. This is the most likely case for disassembly since the axle is meant to be a tight sliding fit in the CV joint, rather than an interference-fit. If you encounter a sticky one, inspect the upper-most portion of the splines (above the groove for the locking ring). It's most likely that you will find some minor burrs on these splines. Stone them away and try again. If you must use hammers and drifts, use proper ones; lead or brass for the hammers, bronze or brass for the drifts. On reassembly the internally splined cup-washer must be compressed, a task most easily accomplished with a hydraulic press.

Failure to maintain the original spline/tooth orientation often causes the axles to bind in the CV joint hub during reassembly. Take it apart, verify the alignment and try again.

Sermonette

The Bentley manual neglects the CV joints, offering neither a nominal lubrication interval nor torque values. The Haynes manual sez to inspect them but to leave them alone unless the boots are torn or leaking. That is as invalid as the Bentley approach; by the time the things are torn or leaking you'll be faced with the expensive replacement of the CV joint rather than its messy but necessary lubrication. (The Haynes method is correct for the older swing-axle trannys and may well be a typographical blunder, albeit one of major proportions.) John Muir sez keep your CV's greasy and they'll last a long time. Despite his many errors and omissions, John Muir's approach is the most correct of all, at least when it comes to CV's.

Each of the manuals cited above claims a certain degree of expertise yet each contains many errors, some minor, some catastrophic. (The Chilton manuals are not worthy of mention.) Your wisest course is to gather as much information about your vehicle as you are able, and from as many diverse sources as possible -- and then to think for yourself.

-Bob

1 comment:

Fred said...

Advance Auto Parts now sells
Brake Grease in small tubes.
Ive had to ask alot for this,
but they now sell it.
Fred Whitmore