Outer CV's

B

Bill Trainer

Well-known member
Hi,

I run an H-Prod VW MK2 Scirocco with a welded diff and have developed a chronic drivers side outer cv joint breakage issue. I am now losing one every event - any suggestions on how to fix it?

Thanks
 
Are they new axles each time? Are you checking the grease in them? I know Don Walsh was having issues with axles and we found out that the axles were coming with very little grease in them.
 
Have you checked to make sure that your engine and trans are not installed offset toward that side? I've had good luck with CV joints (knock on wood) but did note on my last engine install that if you shifted everything toward one side or the other (using the std slots) that you could nearly get an axle jammed axially.

Al Seim
HP Scirocco 1.6
 
Bill,
For insurance, take the CV cages and radius ALL of the edges with a Dremmel tool. It will take you an afternoon to do several cages, but they will be stronger.
Peter
 
What Al says. Make sure that the motor is centred and pack the CVs with Redline or a quality synthetic grease with moly like Valvoline.

How low do you have the car? Are the CVs running at a steep angle?
 
I tried new aftermarket and they did not seem to last at all so I have been cleaning and re-packing OE ones (used). I have never looked at the engine centering.. that could be an issue. This seems to have gotten worse after I lowered the car 1.5" - I still have 3 3/4" of clearance at the A arm. The axles should be level. Thanks for your suggestions!
 
Also, try to get most of your camber at the bottom of the strut. This will widen the track a bit and give the axles a little more room. You can use those eccentric adjusting bolts on the top and bottom holes of the strut mounts.
 
Bill, are you using the Hoosier radial slicks? I had a concern that they have too much grip for running a welded diff. We put one in the wife's GTI last race and broke an outer joint after one qualifying race.
 
Bill was running bias plys at the Cat.

I agree with the assessment that the problem is related to engine alignment.

If the engine has shifted left or right, you could be running out of 'plunge' travel causing the CV joint to bottom out.

I think Kevin Ruck had a similar problem when he transitioned from IT to Production...running the car lower was causing the CV joints to bottom out.

If I recall his solution was to use custom axles that were slightly shorter in length.

Easy way to check is to grab the drive shaft and try to move it in and out at different bump heights and/or steering angles. There should always be some travel other than at crazy extemes of steering lock.

Edit: The limited prep rules do allow you to modify the engine mounts to allow for CV joint alignment as an alternate to making custome drive shafts. Exact wording from the GCR:

Transverse engine cars can rotate the engine about the
crankshaft centerline to align axle shafts/constant velocity
joints.
 
Improved Touring VWs used to have issues with axle length when running large neg camber. The sign for this issue was the on the inner joint end with the small end of the axle that sticks out past the circlip hitting the seal inside in the center of the trans axle flange. Thats the rubber plug that you remove to take off an axle flange. When the seal gets beaten up they leak trans fluid out of the flange and inner CV. I really could not see this happening with 1/2' negative, but with the car lowered maybe there is enough geometry change? BSI used to modify axles to make them about 1/4" shorter but they seem to have moved over to all Miata stuff.

I would look at the quality of the replacement parts. Not all CVs are the same quality-even the German ones. Are the bearing slots getting a worn area and pitted or are they just exploding?

Of course you may just be making too much power and need to tune it back some.
 
Make your lower control arms longer and the problem will most likely go away, once you've determined that your motor is in the center of the motor mounts.

MC
 
You are somehow end loading the axle shaft against the trans. Is the lower strut brace good? Put the car on jack stands and loosen the outer CV big nut and check the axle plunge with A arms in the loaded position. You need 1/4 or so plunge. You should get years out of the outer joint.
Chuck Mathis
 
Thanks for all your help - took a quick look at the engine centering and boy - it is offset to the driver side!! close to a 1/4". I have plenty to go through this weekend with your suggestions, thanks again.
 
My race book tells how to measure axle plunge and how to fix it.
Short story; Back off the axle nut 6 turns, push the axle in, ( at race ride height, not jacked up).
. It should move about 3/8 - 7/16 in. Move the engine around until both are even. The A 1 is really weak in the engine bay/mounts etc.
You can adjust the ball joint's bolts holes also. .
I also make race axles, with 4130 CV cages and loose fit CVs. Stuffed with Mobil one synthetic grease, they last with our HP Rocco and turbo Jetta Chumpcar . both locked. I repack them every 20 hrs or so.

But all of the above advice is valid. Paint the plastic seal to track the axle hitting the bottom.
Remove one axle bolt and check for trans oil running out, etc.
Often the replacement axles are not the right lenght. They fit on the street but will not work at lower height. HTH, MM
 
Thanks again for all the advice, I can certainly do a better job of getting the drive components aligned.. but this was simply a case of the cv boot ripping and the joint drying out. I was surprised when I removed the half shaft that it was still intact. Of course the joint was baked dry and "hung up" - would have shattered if on the track much longer. I would feel better if it had shattered due to mis alignment of the engine.. a torn boot is kind of lame to lose 2nd place.

thanks
 
Well.. was at the Kettle this weekend sorting the car. Although I had 3/8 to 1/2 axle play on both sides I made 9 laps of qualifying and the drivers side axle broke on the first lap of the race. In qualifying I did go off at turn 6 due to oil on the track but it did not seem particularly hard.

Since I lowered the car (1.5 inches) the drivers side axle has broken every event (5 events). I am going to raise the car back up - I never had a failure before.

Worse however was being naive enough to think I could be on the track with the SM drivers. On the front straight going up the hill before the green flag even came out the SM behind me hit me 3 times in a row!! since I have no bumper it mashed in the back, I was stunned. I will never be on the track with them again.

Not really a good day. I am stumped on the axle issue - I need to complete races again.
 
After you lowered it did you check axle to unibody clearance? Look for shiny spots on the axle shaft.
Chuck
 
Bill,

This is a well known VW trait. Only use Lobro joints and the factory lube (a synth) or redline/lubri-moly/synth cv grease.

What worked for me was having the first set of offset control arm bushings made (circa 1994). They were installed just before one of the "Longest Days of Nelson Ledges" and there were no failures for me since then.

They certainly look like the ones here: http://www.lellaautosport.com/mk1-delri ... hings.html

You want them offset to move the control arm outwards freeing the inner cv from hitting the trans seal. Don't forget to pin them in the orientation you want.

That will let you lower but you can certainly go too far. High spring rates will handle the roll center evils.

Good Luck,

DZ
 
Bill,
You have either crappy Discount axles,or the wrong axles, or the engine is moving and smacking the bottom.
Please do this, remove the axle and clean the drive flanges. If the axle bangs the bottom a lot, there will be shiny marks verifying impact. If ther are no hard shiny marks,,the axles are not hitting. I paint the drive flanges with "chevy orange" to track interference.
Was the engine centered in the car RE to the axles?/ Was the plunge measured per book, at ride height, with 3/8 in or more travel potential? The car can be really bent and not brake axles,as long as the axles have room.
Do you have good lower control arm bushings?? The A 1 has very small OD and really wont move much, while the A 2 LCB are much bigger and need some looking after.
Other areas that allow travel, strut inserts, ball joints, strut bearings.
Plunge can be increased @ a few points, Ball joint slotted holes, eccentric bushings, taking more camber @ at the strut to knuckle,less @ the strut top, using a lower stress bar between the lower arm bolts/ frame horns. These are really weak in early cars.

If all of the above shows plenty of plunge room, than you need a better built axle. Finding the OE axles can be hard at this point. But if you do;. 1) grind the inner ends to the C clip,
2) grind the slots in the cages where the balls pass through.
3) Pack with Mobil one synthetic grease.

4) Buy 4130 caged axles from me. I need your sizes, with plunge measured before I build your cores. They are 200$ per. I have not had any failures , if repacked @ 20hrs.

I run my cars very low, well under flat control arms, I dont break axles.

Edit. I seldom have seen axles ht the driver side body, but take a look, I often smash the body seam for a little more clreance. Mk 2 pas side needs some love for sure.
HTH, MM
 
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