I'm replacing the CV rubber boots on my '91 Golf but am having trouble with the six Torx headed bolts that attach the driveshaft to the differential. The T40 socket I bought from Halfords seems a loose fit in the bolt heads and has just slipped in a couple of them. I have managed to remove a few of them using an allen key and applying some heat but am worried about damaging the heads of the new bolts when trying to do them up to 33lb ft torque.
Does anyone have any experience of these bolts and the best way to undo and replace them? Thanks.
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Yes a lot, I use a draper torx which is a perfect fit on the Golf and Polo and have no problem. The fit is very snug. I would comment that the Draper set is VW specific and has Torx for head bolts and drive shafts. If you use an allen key you will damage the head and end up buying new bolts ( £1.70 plus vat each ) Good luck Regards Peter
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Peter,
When you say that the Draper set is VW specific, I assume you mean that the set contains the drive key sizes that suit the various Torx fasteners on the VW, not that the drive keys for VW have a special fit?
My experience of Torx stems from my days as a standards engineer for an engine manufacturing company at which time I was quite deeply involved in investigating, testing and specifying them.
All Torx fasteners and drive tools should be to the same Torx standard, as laid down by Camcar Inc. If they are made to this standard they will be a very snug fit. If they are a loose fit, either the wrong size tool is being used (likely) or one or other of the parts hasn't been made to the Torx standard (most unlikely).
As I said in an earlier thread, Torx keys give up to 1200 times the tool life compared with Allen (hexagon) keys and are far kinder to the fastener. With Torx, the drive angle is 15 degrees whereas Allen keys have a 60 degree drive angle and thus can slip or split open the fastener head if conditions are not optimal.
Incidentally, I'm always a bit wary about Draper tools - maybe I've just been unfortunate in that those I've bought have not been very durable (footpump, ball joint splitter, etc., not Torx tools). I use a Pickavant Torx driver set and have never experienced any problem with slippage, etc.
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I've just had another thought. Are you sure that the fasteners (bolts/screws) are Torx and not tri-square? They do look similar. Tri-square are used on some Vauxhall cylinder heads and using Torx keys on these has been known to give rise to complaints of poor fit and slippage.
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Incidentally, I'm always a bit wary about Draper tools
What *would* you recomend?
I actively search out Draper or Stanley; I can't afford Snap On.
What should I be looking for as a home maintainance enthusiast?
--
Parp, Parp!
Note: All Toad posts come with an implied smiley.
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Difficult question! I suppose it depends on the intended usage.
That, is, if it's just a one-off job and the tool won't be highly stressed, then I'd go for the cheapest that looks like it might do the job.
If it is likely to be of use several times, and especially if it has a hard job to do, then I would invest in something like Snap-on or Pickavant. I find it much more satisfying anyway to be working with quality tools.
For spraying, I have a Devilbiss JGA gun (expensive) even though my compressor is a home-improved tractor tyre pump! The compressor/reservoir (a large Calor gas bottle) can supply only enough air to spray one panel at a time but I still get satisfaction from handling a quality gun.
In my earlier years of D-I-Y car repairs and servicing, I used to put by a small part of the cost saving of each job to buy a decent piece of equipment. Some of this equipment has been of service to me for 40 years so it has been a good investment.
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THEY'RE NOT TORX!!!!!!
You need a 12-point spline drive bit, M8 I think.
You may well have b*****ed the heads up.
Don't worry about the quality of the tool, just make sure you use the right one. I use a 'Laser' spline drive kit that was about £4. G&S sell a similar set for less than a tenner, Halfords want £20 for a set including half a dozen sizes you'll never use.
As for torquing the driveshaft bolts back up - you'll be lucky to ge a torque wrench in there. Put loctite on the threads and make sure they're tight, that's all.
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I am not at home to look at the tool but I think you are right Dizzy they are wekk machined Tri Squares both dor the Head and the Drive shafts, thats why they are VW specific, although of course other manufacturers do use these fittings.
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Caspar,
So we've established that the bolts are tri-square (12-point) and not Torx. You may have damaged the bolts but I think the damage will be on the 'undo' side only, and may well be insignificant, so you should get away with it.
Since they are tri-square, it is obvious that VW intended them to be very tight (although Torx drive is almost as strong). As Robert indicated, you will need to do them up as tight as you can manage - I don't think you will over-tighten them with the tools that you are likely to have.
I agree with Robert - use a drop of Loctite to ensure that they don't work loose. High tensile bolts are not very elastic, and it is elasticity (stretch) that prevents them loosening. If you can't get them to the specified torque they will not have stretched enough. You need a Loctite that is strong enough for the job but not so strong as to prevent future removal of the bolts.
If you can find it, you need Loctite 243 (Nutlock). Screwlock (225) is not really strong enough and Studlock (270) may be a touch too strong. Loctites with a number beginning 6.. will almost certainly be too strong. (Note: I may be a bit out of date with these numbers but they will give you an idea what to look for. Your local friendly garage may let you have a drop.)
Incidentally, high strength Loctites can be weakened for removal by heating to 200 degrees C, or 300 degrees for the very high strength grades. Not easy on things like drive shaft bolts, or near oil seals etc., but can be done.
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For any kind of socket head bolt (Allen, Torx, 12-point or whatever) it is important to ensure the drive bit is very firmly seated in the socket. This means scraping out all the dirt and gunge first (fine bladed screwdriver) then tapping the drive bit gently into the socket until it contacts the bottom. All these fasteners seem a bit marginal for torque loading unless the bit is in perfect condition and fully seated. I have rounded off several Torx head bolts on Fords despite using the right size drive bit, and once had to lop the head off a Polo driveshaft bolt with an angle grinder to remove it.
Richard Hall
bangernomics.tripod.com
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Thanks for all your replies.
The bolts do have 12 splines so it looks like you are right. A 6mm Allen key fits so I suppose I need a 6mm 12 point spline drive bit. Just a matter of finding one now!
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Caspar,
You need an 8mm - the size is measured point-to-point, which an allen key won't reach.
Have you undone the driveshaft nut at the wheel end okay? It can be very tight.
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For any kind of socket head bolt (Allen, Torx, 12-point or whatever) it is important to ensure the drive bit is very firmly seated in the socket. ... All these fasteners seem a bit marginal for torque loading unless the bit is in perfect condition and fully seated.
Richard, I couldn't agree more. Let's go into a bit more detail ...
Allen screws are becoming obsolescent now, mainly because of their high cost. This is due to the fact that they need to be made of a high steel grade (at least 10,9) because of the tendency for the heads to crack across the corners. A high grade steel is more expensive to buy and forming the head is also costlier for higher grades. With an Allen screw, the main danger of insufficient key engagement is splitting of the head, and once that happens the key will just slip.
Torx screws are now far more popular because the heads are inherently stronger, so the screws can be made from a cheaper steel (typically 8,8) and the heads are easier (and thus cheaper) to form. However, because Torx has a stronger head, the socket depth has been reduced in comparison with Allen screws (to ease head forming) so it is equally important to make sure that the socket is clean and the tool fully seated.
I believe that Tri-square is made to a military specification for very high duty applications. A tri-square screw will be made of a very strong steel and be very costly to make. It will be used only where there is a need for a very strong fastener in a recess or other confined space. Since they are for high duty use and they are in a strong and low-elasticity steel, tri-square screws will have a high tightening torque and it is very important to make sure they are properly tightened.
Richard and I mentioned the use of Loctite for Casper's drive shaft screws but, thinking about it again, this should really be a very last resort. If the use of Loctite will reliably avoid the need for a high tightening torque, then I think VW would have used a Torx screw with Loctite. As an off-the-cuff example of what I mean, the drive through the shaft to the wheel may rely partly on the friction between the drive shaft flange and the hub it attaches to, and this friction may in turn rely on the screws being pulled down to a specified torque. An insufficient torque could lead to fretting between the flange and the hub and eventual looseness.
Here endeth today's lesson!
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