Sheared outer CV spline - reliable solution for hard use?

I broke an outer CV when launching off the line on Sunday and looking for improving the reliability of them. My setup is on a MK1 using cabby shafts with MK2 GTI outer CV's.

I have seen Terry47's posts on his setup and that might be something I can do over the winter but looks to be quite involved and will require a bit of thought and planning. In the meantime, I need to get a short term solution going.

http://www.clubgti.com/showthread.php?251178-Breaking-CVs&highlight=breaking+cvs - Babbe and Terry47's thread

The car runs slicks, plate diff and a Tilton cerametallic 4 puck unsprung clutch with a high torque pressure plate. I got good heat into the tyres on the warm up lap but it is quite difficult to feed out this clutch and manually 'slip' it as I would with a normal setup.

I am going to replace with new CV's as this will get me going again quickly but I was wondering what folks thoughts on shot peening were, would this improve the fatigue or shear of the outer spline to the radius of the CV 'hub' where it has broken?


I think it has ultimately broken through the sudden shock of the clutch locking instantly and sending everything through the drivetrain, breaking the weakest link which is the outer CV in this case.

















CV's were brand new 'Meyle' items from Germany.

Options...

• Motorsport driveshafts & CV's - Expensive (No final price but estimate 1K after speaking to GKN and a lot of faffing around!)
  
  
• Larger VR6 CV's - I think this would mean having to change to VR6 hubs and do not want to do this now as would have to change caliper brackets, shock mounting holes, 5 stud wheels, new ball joint mounts etc
  
  
• Shot peening my 'original' MK2 GTI outer CV's - Keen to try this
• Installing 'clutch delay valve' - Restricts flow of fluid back to Mst Cyl and effectively 'slips' the clutch depending on ID of orifice
  

I am very much thinking of sending away a new set of outer CV's for shot peening and also installing a CDV. Tilton do a 'flow restrictor valve' but this is expensive at just under 200, albeit it does get very good reports from drag racing folks.

Any input on the shot peening process, specifically whether this sounds like a good idea for the outer CV's?

The chap from GKN said that the complete driveshafts were usually the preserve of WRC and BTCC boys and not cheap. He suggested shot peening new CV's and that it would be much more resistant to stress fractures developing and ultimately with a failing joint.

Cheers,
Ali

 

I would be inclined to blame the first failure on a faulty part. I remember doing Rallycross in the nineties (8.2" Avon A2, plate diff etc) and not having a huge problem with CV's. Didn't have huge power / torque though, but used nearly 7-8k full throttle starts...

 

Goof did suggest that at the track and it is true that it could be down to that. However, with the use and the drivetrain + 370 bhp at 3700rpm being put through them, kind of feel as if it is ****ing in the wind.

Hoping with 'good' CV's + possibly having them shot peened with the addition of the CDV, might get me through the season.

 

That is some revs you have dialled in there btw!!

 

I know. The cam I used to run would die if the revs dropped below 5.5K. A VWMS gearkit was needed as the power band was 2000 rpm wide.

 

In my opinon the best choice is VR6 CV:s and just get some vr hubs and put in your old upprights.

 

Have you considered a clutch plate change Ali?
Maybe go to a sprung plate with 400lb-ft clamping load?
Or doesn't such a beast exist.
I seem to recall Helix could offer a suitable uprated plate from when I had my S3. Solid flywheel to replace the dual mass effort (as you already have) but with a plate with a bit of give in it?

 

Do you mean installing VR6 drive flanges (in order to accept bigger splines from VR6 CV joints) into my existing hubs? - When I say 'hub' I mean the complete unit where caliper mounts to, ball joint & strut etc.

Is this possible into a MK1 golf hub/bearings etc?

 

My rally Pulsar on full boost starts will slip the clutch on a hot day, probably an easy 'cush drive' as talked about above. Alternately, just give it less beans off the line.................you can always mash the carpet gradually once rolling

 

I suppose that is an option but not really that keen tbh as I have already spent a lot on getting that setup together and don't want to start messing with it - right or wrong as that may be - and otherwise, its working well.

Good suggestion and will give it some thought though.

 

Older CV joints John talks about to yours may ave differed in material and heat treatment? Making the newer ones cheaper to produce however, reducing there tensile strength.

 

He sure did.

I think Ali and Craig looked into going the Mk3 hub route - Craig still has my spare hubs/ARB etc.
I suppose I should really go get them back at some point lol

 

shame hub reduction is not an option its a fabulous idea and can deal with massive power

 

Mushy, that sounds like a possible way forward long term...

How do I go about fitting vr bearings?

Presume that allows me to run vr drive flanges with a mk1 hub and then either change all wheels to 5x100 or to weld and re-drill 4x100?

 

Smudge, have you any suggestions on decent quality cv joints?

Thinking GKN but can't seem to find any that easily!

 

I have no experience with upgraded items I'm afraid, there was a good post by RobT on this I think, I will have a search...

 

Craig has gone MK3 now. Wide track, better btm balljoint position/more castor and bigger cv's obviously all good advantages.

Hub change won't work for me as you know as means too many changes.

 

Eurowise do heavy duty driveshafts for their Mk1 VR6 conversions, might be worth a look?

 

There is some CV info and material selection in here, but it's a driveshaft thread predominantly.