wozza Posted November 15, 2018 Share Posted November 15, 2018 Has anyone had a 4340 stub axle break off at the theads? I have attempted to contact Joe from Chequered Flag Racing / Modern Motorsport as this is the stub axle he sells, but I have not heard back, I know he is on this forum so I hope to responds. The stub axle was purchased this year and has only done 30 miles The failure point is not under load with engine torque or torque forces caused by sticky tires. The only failures I have had with standard stub axles is the wheel flanges failing. The nut was not over torqued and CV axle is not too short and pulled the threads off, there is more than 1.5 inches of plunge extension left and my suspension has very little droop My analysis of the failure. 1. Design. The threads are machined all the way to the step causing a large stress riser at the failure point, I have included a picture of the Modern Motorsport theads next to standard theads, You will see on the standard stub axle the threads stop well short of the step and have a nice radius 2. Hardness. I had the 4340 stub axle hardness tested, result was more than 51 HRC (Hardness Rockwell C scale) Carroll Smith's book 'Engineer to Win' states 42-44 HRC range for E4340 hubs, axles and torsion bars, Aircraft landing gear are also made from 4340 and need to be in this range too. Did I get an incorrectly machined and heat treated stub axle set? If there are any Metallurgists out there I would like their opinion too and looking forward to hearing from Joe. Quote Link to comment Share on other sites More sharing options...
LLave Posted November 16, 2018 Share Posted November 16, 2018 I think we should all hold from speculating until the vendor has had a chance to respond. I will PM you the contact information I have for Joe at Chequered Flag. 1 Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 16, 2018 Share Posted November 16, 2018 Both of you should just post your contact information to see if it's the same. It is a business, not a private residence. And how long have you been waiting for a response. One month is not the same as one day. And post the actual torque value used, not "correct", and any details like if never-seize was used. Plus any other details, like maybe peening the lock nut crimp in with a sledge hammer. No reason not to speculate. That's what the forums are about. Joe doesn't need protection. The design elements shown are not very good, as far as stress risers are concerned. Kind of surprising. Does that hardness test take in to account the curvature of the shaft? Quote Link to comment Share on other sites More sharing options...
wozza Posted November 16, 2018 Author Share Posted November 16, 2018 It appears I have his yahoo address that he was using in April so thank you LLave for his new address. I will email him shortly Regarding torque, Haynes manual is 180 and up to 240ftlb if required to meet rotation torque requirements. 180 is about the most I can achieve with 1/2inch drive socket and I have never had a problem before. I lube all my threads,I use a lanolen product unless its an engine/gearbox etc. Good for your hands too! Regarding peening with a sedgehammer, I didnt need the sledgehammer this time, its got a stiff nut, I think its from a 280zx? nowhere to peen it. Curvature of the shaft does change the hardness reading but at this diameter its only .5 HRC Quote Link to comment Share on other sites More sharing options...
LLave Posted November 16, 2018 Share Posted November 16, 2018 15 hours ago, NewZed said: Both of you should just post your contact information to see if it's the same. It is a business, not a private residence. And how long have you been waiting for a response. One month is not the same as one day. And post the actual torque value used, not "correct", and any details like if never-seize was used. Plus any other details, like maybe peening the lock nut crimp in with a sledge hammer. No reason not to speculate. That's what the forums are about. Joe doesn't need protection. The design elements shown are not very good, as far as stress risers are concerned. Kind of surprising. Does that hardness test take in to account the curvature of the shaft? Good point. I just looked, the contact information is right on their website: http://www.chequeredflagracing.net/HOME.html Joseph Siam <jsiam1@earthlink.net> Chequered Flag Racing .net Joseph P. Siam 9833 Deering Ave unit I Chatsworth Ca 91311 818 350 6222 Quote Link to comment Share on other sites More sharing options...
Miles Posted November 16, 2018 Share Posted November 16, 2018 (edited) Typical failure point for stock stub axles. My stock axle snapped in the same location at 5 mph while pulling into traffic. So I replaced both axles with the 4340 axles torqued to 180 ft-lb. OK so far. Testing is the only way to know why the axle failed. One option would be to pull the other axle and have it X-Rayed. For the axle that failed, you could have it X-Rayed and lab tested for tensile strength, hardness and chemical composition. Joseph Siam would probably welcome test data to improve his product. Something he should be doing anyway. Attached picture shows typical stub axle failure. Edited November 17, 2018 by Miles Quote Link to comment Share on other sites More sharing options...
SH4DY Posted November 18, 2018 Share Posted November 18, 2018 (edited) This just happened to me today installing my WHP 39 spline chromoly stub axles (ZXT companion flange). Installed at 180lb/ft, then gradually tightened until 750g breakaway weight at the hub per manual (maybe another 1/3 turn). And NOT using an impact. 3 hours later I hear POW! and find the flange and nut on the ground. Fortunately the car is sans drivetrain right now and on jack stands ie 0 miles, no burnouts, launches, etc. I emailed WHP but its the weekend so, waiting for monday. Wanted to add to the thread though in case there is a common vendor issue. Very odd coloration at the fracture... Edited November 18, 2018 by SH4DY Quote Link to comment Share on other sites More sharing options...
wozza Posted November 18, 2018 Author Share Posted November 18, 2018 The grain looks a little different to mine, mine looks more crystalline. But that could be in the photo. I would be interested to see a hardness test on your one. Quote Link to comment Share on other sites More sharing options...
SH4DY Posted November 18, 2018 Share Posted November 18, 2018 Mike @ Whitehead got back to me this morning ( Sunday- that's pretty solid customer service) and said they had a batch of 27 spline axles that had been annealed incorrectly and were all recalled. Mine was the first reported 39 spline failure but he sent them the pictures I took to see if it is a similar defect. If so, they'll probably replace them. I keep this updated. 1 Quote Link to comment Share on other sites More sharing options...
JMortensen Posted November 18, 2018 Share Posted November 18, 2018 FWIW I think that spec of torquing until reaching the correct drag on the axles is BS. I know, heresy, it's right there in the FSM, but what is happening to increase the drag? Are you squeezing the spacer so hard that it's distorting? Doesn't seem likely, but that's really the only way that I could see it working. Torque specs for fasteners generally have something to do with the bolt stretching. I'd like to see a torque spec for these based on the size of the thread, not the drag at the hub. Quote Link to comment Share on other sites More sharing options...
SH4DY Posted November 18, 2018 Share Posted November 18, 2018 I agree. Next time around if there isn't any in/out play at 180lb/ft I'm going to let it ride. Quote Link to comment Share on other sites More sharing options...
wozza Posted November 18, 2018 Author Share Posted November 18, 2018 I Also agree, end float is what you need to check and that is determined by spacer length. A quick Google of torque specs for m20 bolts 4.8 grade is 166 lbft, a 8.8 grade 321 lbft. I hardness tested a standard stub axle too, comes out at 15 to 20 HRC on the shaft and 9 HRC on the flange. 20HRC is around a grade 8.8 bolt Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 18, 2018 Share Posted November 18, 2018 (edited) Nissan has several adjustment procedures in the FSM that can conflict, then they don't have specific "readjust" instructions. The rear bearings are pretty simple, you're just clamping a spacer, the "distance piece", between two bearing inner races. Unless the distance piece is thought of as crushable, there is no adjustment possible. The parts are all supposed to be measured and fitted before installation, then torqued, and that's about all you can do. Are people confirming that their distance pieces are parallel on the ends, and the bearings are seating properly? A little tilt would put a lot of leverage on the shaft end. There are five surfaces that need to be parallel. Just some things to consider. Edit - one more thought. If it was mine I'd assemble the stack of two bearings, the distance piece, and the nut together outside of the hub as a quick check of specs. If it's close to right there won't be any gaps. If it's not you'll probably see something. Could be the threaded ends are cut off-axis, which would put the nut off. Edited November 18, 2018 by NewZed Quote Link to comment Share on other sites More sharing options...
SH4DY Posted December 10, 2018 Share Posted December 10, 2018 Just to update: WHP advised me to try to torque the other stub axle per FSM specs and see if it would fail as well. And it did. Except I realized that my wrench only goes up to 150 lbs/ft so the initial failure was also at less torque than I thought. Anyway, this one didn't fail as spectacularly: I torqued to 150, then tried the hub resistance in 1/4 turn increments. On the 3rd or 4th try, the resistance fell of significantly and I thought the threads had stripped. Nope, it just split about half way into the nut so it was still partially threaded. They are supposed to be making a new batch and shipping me some. 1 Quote Link to comment Share on other sites More sharing options...
wozza Posted December 17, 2018 Author Share Posted December 17, 2018 Update from me, Joe from Chequered Flag Racing has been in contact with the Manufacturer and they have agreed to replace my stub axles too when they make a new batch. Thanks Joe. 1 Quote Link to comment Share on other sites More sharing options...
Nelsonian Posted December 23, 2018 Share Posted December 23, 2018 (edited) So was it deemed that there were complications with or a bad batch of stub axles that went out? Was Joe currently in the process of making new ones? Edited December 23, 2018 by Nelsonian Quote Link to comment Share on other sites More sharing options...
Miles Posted December 23, 2018 Share Posted December 23, 2018 No quality control. Ask the supplier if parts are lab tested before they are offered for sale. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted December 23, 2018 Share Posted December 23, 2018 No quality control? How long have these been for sale? Since Ross was selling them at Modern Motorsports, maybe 15 years now? How many have had this problem? Sheesh. Quote Link to comment Share on other sites More sharing options...
wozza Posted December 23, 2018 Author Share Posted December 23, 2018 Joe's Manufacturer is replacing them at the next production run, that is in 8-10 weeks from now. Quote Link to comment Share on other sites More sharing options...
ritrebor Posted December 23, 2018 Share Posted December 23, 2018 Wozza when did you buy your set? I got a set from Joe around August of last year but I have not installed them yet. Just want to know if they came from the same batch. Thanks ritrebor Quote Link to comment Share on other sites More sharing options...
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