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BrandenZ

Wolf Creek CV axle bind

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I'm having a very bizarre issue with the Wolf Creek CV axle kit, some relevant points of note:

1973 240z

Subi R180 diff with johnc side axles

Toe bushings adjusted bringing LCAs as far inboard as possible (for extra wheel clearance) while maintaining 0 toe

Kmac camber bushings with ~1.8 degrees negative camber dialed in

 

On the initial install, axles measured at 15-3/4" length, I had major install issues and had to loosen and swing the LCAs out. At ride height, I noticed I could barely move the driver's side axle laterally with my hand. Casually driving, there were no issues. Under WOT (LS2 T56 btw), I get what feels like aggressive wheel hop but isn't.

 

After teardown, I noticed the driver's side inner safety wire was chewing into the adapter bolts. Both inner adapters looked like this, showing clear signs of interference:

https://www.dropbox.com/s/llliattb2slzaa5/20200111_165439.jpg?dl=0

 

I suspected I was right on the edge, so I took both axles to a machine shop and had them remove 1/4" from each side, 1/2" total. The current axle length is 15-1/4" in total. On re-installation, the passenger side just barely fit with both adapters installed. On the driver's side, I had to drop the insulator / strut assembly about 1/2" for a little extra droop to get it in. Now at ride height, I can freely wiggle the driver's side axle laterally quite a bit. Unfortunately under WOT, I'm experiencing the exact same issue. The axle seems to still be 'slamming' into the inner adapter during heavy acceleration. 

 

The best next step I can think of is to drop the collar fully on my coilovers and see if I can re-produce the bind by jacking the tire / LCA up, and to measure center to center at varying points from full droop to full jounce.

 

I can't find any posts describing any similar issue with CV conversions, so I'm a bit baffled at what I'm experiencing. Any thoughts or ideas are very welcome here! Thanks in advance to anyone who may be able to help me... ahem... out of this bind! 😅

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I've read the same about droop, but anecdotally I have to disagree. I added droop by dropping my coilover to fit the axle in the driver's side, meaning I added length. Also on the initial install, at droop I could feel lateral play in the axles, but dropped at ride height I could not. For my suspension setup, jounce definitely is a shorter length situation with the axles. 

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The axle will be fully extended at full droop. 

 

Sounds like your combination of adapters etc just means your axles are too long. Have you verified with Wolf Creek/Futofab that you have the correct lengths for your application? If one side is still in a bind, the problem will persist. I can't remember on the R180's if the driver and passenger side axles are symmetrical or not, might be worth verifying your measurements. 

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I agree with @Ben280.  Even if the Wolf Creek axles are same length as stock half-shafts, that doesn't account for the fact that the aftermarket side axles *may* add some length to the overall system (as compared to the stock Datsun side axles for a non-LSD R180).  And you mentioned you have your LCA adjustable bushings turned in the way....how much did that change your effective LCA length by?

 

I would guess the cheapest solution at this point would be to trim the axles (again), or push the LCAs back out to stock position.  What application is the car used for?  

Edited by jhm
Clarity

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Thanks for the replies! I contacted FutoFab on the issue but have yet to receive any response back. They sell the johnc side axles with the kit now, so in theory I'd expect them to work together with it. That said, empirical evidence seems to suggest otherwise...

 

Axle length checker lathed out of PVC:

https://www.dropbox.com/s/2t7c7bfbdy3z0fm/20200119_165400.jpg?dl=0

 

Then after accounting for plunge on the CVs,  custom mock-up axle lathed from delrin:

https://www.dropbox.com/s/lbcrm5q7ygneaj9/20200119_191158.jpg?dl=0

 

Seemingly correct axle length:

https://www.dropbox.com/s/5kscrhxp2rzsvc1/20200119_193101.jpg?dl=0

 

An interesting point of note is that even with the 15-1/4" length axles, there is not bind in the traditional sense of absolute length. What's happening is that the combination of the axle length and plunge distance available in the CVs allows the axle to drift enough that it _will_ contact the CV adapter on the diff side before stopping / resting on the circlip on the outboard edge. I am very, very dramatically experiencing this under load. Perhaps a lower torque output Z would not, I'm not sure.

 

Anyway, the correct length for my application appears to be 14" drivers side, 14-1/4 passenger side. This is a HUGE difference from the 15-3/4" original length axles I was shipped. Unless I was sent the wrong axles, or my understanding of what's happening here is grossly incorrect, I'm not seeing how this kit ever works on a Z (although maybe it's correct for the longer wheelbase 510). I'll report back my findings if / when I'm able to correct this... though it sure is tempting to just slap my old half-shafts back in at this point!

 

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FWIW, I'm running the Wolf Creek R200 Axles on my car and haven't had this issue with them. Thinking it through, since the R200 is wider, you'd be stretching the axles on a R180, not over compressing them. 

 

1.5" difference seems like too much, and leads me to wonder if something else is off with your setup? It might be time to cycle the suspension through its range on each side, and turn the axles to see if you can further isolate the issue. 

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I'm at my wit's end with this kit. I'm down to 14-1/8" axle length from the original 15-3/4" and am still having issues under acceleration. I swapped back to my half shafts and have absolutely zero issue. At this point, I'm likely abandoning the kit entirely until my half shafts or u-joints break racing. It's so bad that 50% throttle in 3rd gear at 25 mph causes issues. I did 100% having a smoking gun of inner diff side adapter interference. At my current length the circlips should hit first, but dynamic forces and diff shift may still allow it to drift. My suspicion at this point is the 400+ ft/lbs of torque throw the axles towards the diff under load and cause a more severe angular plunge of the CVs than the adapters were designed for. I could verify this theory by possibly lathing out the inner adapters, likely at the cost of strength. Alternatively, I could turn some aluminum adapter extensions hollowed way out to give the kit breathing room towards the diff. Sadly at this point and with no response from FutoFab, and additionally knowing the kit was engineered by someone that's no longer among the Z community, I'm just going to consider this money and time wasted and run my half shafts...

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I doubt the CV is at too much of an angle. The 911 has the transaxle end of the CV something like 2" forward of the hub, then they run camber and they handle it fine. They do have deep pockets for the CVs to move into, you could completely extend the CV in the race and it wouldn't touch anything on the car. I think that's the difference.

As far as the other options go, my LS should be in the vicinity of 400 ft/lbs with Z31T and Modern Motorsports chromoly stub axles and adapters, and aside from CV bolts loosening (fixed with safety wire) I've had no trouble.

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Sorry to hear that you're still having issues.....sounds extremely frustrating.  I am surprised, however, that you're having trouble getting hold of Dave (Patten, Futofab owner).  IME, he's been extremely responsive.  Is this the contact info you have?

 

Telephone - (603) 774-6964

 

Just out of curiosity, which CV kit do you have?

https://www.futofab.com/index.php?option=com_content&view=category&layout=blog&id=38&Itemid=122

 

 
 
 

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1 hour ago, JMortensen said:

I doubt the CV is at too much of an angle. The 911 has the transaxle end of the CV something like 2" forward of the hub, then they run camber and they handle it fine. They do have deep pockets for the CVs to move into, you could completely extend the CV in the race and it wouldn't touch anything on the car. I think that's the difference.

As far as the other options go, my LS should be in the vicinity of 400 ft/lbs with Z31T and Modern Motorsports chromoly stub axles and adapters, and aside from CV bolts loosening (fixed with safety wire) I've had no trouble.

 

Yeah, after pondering on it a bit more I believe I've got two issues. One of them was an absolute length issue due to my setup. Now I believe I have an issue where the provided adapters do not have deep enough pockets. Given that the kit allows the CVs to both slide on the splines and plunge in both directions, I believe under load it's enough slide and plunge for the end of the axle to contact the adapter. I could probably resolve this by either adding a circlip groove on both sides of the CV, only allowing movement with plunge, or possibly machining an adapter spacer with a very large groove. Whatever the final solution is here, I really really want to keep my R180 clsd...

 

1 hour ago, HuD 91gt said:

Did you ever move your LCA’s back out to stock length prior to shortening them once again?

 

Unfortunately this isn't really an option for me with my wheel and tire setup. If I spin the LCAs back out, I run the risk of the sidewall of the tire contacting the fender / lip. As a side note, my half-shafts have zero issues running with my current LCA and camber plate setup.

 

37 minutes ago, jhm said:

Sorry to hear that you're still having issues.....sounds extremely frustrating.  I am surprised, however, that you're having trouble getting hold of Dave (Patten, Futofab owner).  IME, he's been extremely responsive.  Is this the contact info you have?

 

Telephone - (603) 774-6964

 

Just out of curiosity, which CV kit do you have?

https://www.futofab.com/index.php?option=com_content&view=category&layout=blog&id=38&Itemid=122

 

 

Yep, that's the email address I used. I sent a follow-up today to that address and dave@futofab.com, so hopefully I'll have more luck reaching him. I'll give that number a call later today after work if I still don't hear anything. Also, I have the Type2 (100mm) kit. I also have the STi stub axles, but I got those from John years ago, on I think his first production run of them.

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Hey, just thought of another, simple solution! Non-plunging 930 CVs. Get 2, run one on each side. I'd bet that solves it.

There might be a cheaper source, but RCV makes quality parts: https://www.rcvperformance.com/ultimate-non-plunging-fixed-930-cv-joint-chromoly-cage-and-28-spline.html

Edited by JMortensen

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4 hours ago, JMortensen said:

Hey, just thought of another, simple solution! Non-plunging 930 CVs. Get 2, run one on each side. I'd bet that solves it.

There might be a cheaper source, but RCV makes quality parts: https://www.rcvperformance.com/ultimate-non-plunging-fixed-930-cv-joint-chromoly-cage-and-28-spline.html

 

Hmm this is a very good idea, nice find! I'd need to verify that if I used a non-plunging CV on the inboard side, that the outboard side + available axle splines still had enough room to drift to accommodate for the longest length required. It definitely seems like it should more than adequately be able to do so, though.

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