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stub axle thread pitch and diameter


jl240z

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I dont know if i should ask this on a different forum but I am trying here first.  If i am wrong please direct me to the right forum.  When I got the 27 spline 280z stub axles, in spite of my best and some what limited efforts, I damaged the top threads.  I want to buy a die to chase the threads for the new nuts. I don't know what size to get. I tried the search feature, and we all know how much fun that is, but nothing came up that helps. I tried two places on line that sell the nuts and got two different answers.  The size is supposed to be the same for 240-280 series.  Anybody know or have a link to where the info is?  I did get the stub axels and cv shafts out of a 280zx turbo but they are only 25 splines and the nuts weren't even staked.  I wonder why Nissan put the so called weaker splined axels on a car that was supposed to have more power than the std 280zx?   Anyway I got the right stub axels and am going with the CV conversion kit from Futofab (wolf racing) so I am gonna have a surplus pile of stuff to sell at the end of the project, whenever that is.  They said their kit has been improved and upgraded so this is gonna be a good thing.  Thanks for any help

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38 minutes ago, jl240z said:

I did get the stub axels and cv shafts out of a 280zx turbo but they are only 25 splines and the nuts weren't even staked.  I wonder why Nissan put the so called weaker splined axels on a car that was supposed to have more power than the std 280zx?  

Nissan used a self-locking nut on the ZX's, so no need to stake anymore.  You should too, they're available.  As for damage, don't overlook that the damaged portion doesn't do any work once the nut is past it.  If the threads won't damage the nut, then you might as well leave them that way.

The smaller axle question has been raised before.  Could be that they redesigned it and removed the stress risers that existed in the 240Z design.  It would be interesting to see the two side-by-side.  Or that the ZX suspension isn't as hard on the axles as the Z's.

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I did place the ccmpanion flange of the 280z over the stub axle of the turbo and there is a very visable difference showing how much smaller the 25 spline is. I don't think I will have to worry about breaking anything but stuff happens sometimes. It is probly more likely to break something with the limited slip I would think. Any advantage to save me when I screw up is nice, Notice I said when, not if? I wonder if in addition to torqueing to the correct ft. lbs, if liberal red lock tight is enough instead of staking the nut. I can reuse the nuts off the turbo but they don't have a lip to stake at the top like the 280z nuts had. It is probly smart money to buy new ones and I would have already if I could find then. Anybody know a vendor besides Nissan who sells the right nuts? unsalted of courss

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I was thinking about the 240Z axle weak point.  Borrowed a 280ZX axle picture from here - https://www.fototime.com/ftweb/bin/ft.dll/detailfs?userid=7DC317B08EDB4B2EA837F708D07C9769&ndx=19&albumid=180EC34916C34BD7850ED1A4EBA6F840&pictureid=0F5C07D338644ADBAE151D14EE4BFDF1

and the 240Z from here - http://forums.hybridz.org/topic/49194-differential-cv-lsd-hp-torque-r160-r180-r200-r230-diff-mount/

and here - http://www.thezstore.com/page/TZS/PROD/23-5020R

Notice that the same tiny nut is used, leaving a big stress riser at the base.  The breaks occur on the same diameter.  The larger splined section doesn't seem to be any advantage in strength.  Maybe why they went back to 25 spline.  It does allow a bigger bearing though.

Even the big 300ZX 39 spline axles use a small nut diameter.  http://www.modern-motorsports.com/stub-axles.html

 

240Z axle.PNG

240Z 2 MSA.PNG

280ZX axles.PNG

Edited by Zed Head
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The first pic is the 240z stub axle, the splines end in sharp edge, second pic is a 280zxt stub, they rounded the splines to flow into the threads. I don't know if that helps but some guys are dumping serious torque into 280zxt stubs without problems, perhaps a better quality of steel, better tempering?

DSCN0146.JPG

DSCN0145.JPG

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Thanks, that's the picture I wanted to see.  And there's not a lot of info there really.  I wonder if other things helped also like the thickness of the washer under the nut.  Maybe even the shape of the nut's clamping surface.  I think the breakage is more a flexing/fatigue break, than an actual yield break.  Could be all of the people switching to 280Z axles really just need to switch to 280ZX nuts and washers.

grannyknot was in the process of installing ZX CV's.  Not sure where he ended up.  

 

 

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All they seem to have done for the later nut is incorporate the washer into the base of the nut.

240 nut and washer on the left, 280zx on the right.

Zed, the CV axles are finished and ready to install, I just don't have a car ready to install them into yet.  That's another year away.

DSCN0147.JPG

DSCN0148.JPG

DSCN0149.JPG

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Seems like the ZX flanged nut would be stiffer than the Z assembly.  Interesting stuff.  Maybe it's more than just a lock nut.

I dragged a CV axle and a u-joint halfshaft out the other day and measured them.  But just realized I didn't measure both CV's so need to do it again.  The one CV axle I measured was 1" shorter than the half-shaft.  So, in my case, 1" for an adapter.  Factory issue 1983 CV axles.  I'll measure the other and add it to your thread, just for the record.  Thanks for the pictures.

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4 hours ago, Zed Head said:
4 hours ago, Zed Head said:

Thanks, I will check it out.  I am reading all the other postings on the stub axels.  I too noticed the difference in the nuts.  The zx turbo one has a slightly thinner base but the base is larger in diameter.  Since I have them ill take the advice and try and clean up the boggered up threads before I buy the die and see how they thread onto the stub axels.  Guys thanks for all the info so far its been a lot of help

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About $26 at McMaster for an M20 x 1.5 right hand die.

http://www.mcmaster.com/#2573a81/=11xeukh

But I agree with Zed Head above... Unless you really, really mangled a number of threads, I'd just file the damaged portions roughly back into "shape" with a triangle file and call it a day. If the nut threads on smooth past the damaged spot(s), then you're good.

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 Thanks John

 I haven't seen those types of taps and dies before. I can think of hundreds of times I could have used those tools. A good share of my time spent on a repair is dealing with broken fasteners, corroded threads, etc. These will speed things up.

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  • 2 weeks later...

Hello all, ba follow up on the stub axel thread repair.  I tried the file  repair and touch up for the damaged threads and got nowhere.  it was probly me or my crummy file. So I went on ebay and for $10.95 delivered to my door I got a 20mm thread repair die.  it came in 3days and it took all of 10 minutes to dd both stub axels.  Best $ spent and a real time saving and anti frustration device.  Sometimes just having the right tool pays for itself in one use and in this case it was a bargain.  On to the next task.

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While on the stub axel subject, I have another question.  I wound up with two sets of distance pieces that live inside the rear hub between the bearings. One set is slightly shorter than the other and loosely fits over the axel the other may be a press fit but I an not sure.  The question is does anyone know if the 280zx 27 spline stub axels have  washer spacers on each end of the distance piece  like the 240z? My old pre microfiche parts book shows the washers for 70-73 z but I don't have a detailed parts book for a 280.  I tried to keep all the parts together when I pulled the axles but I may have lost them if they did exist at the time . I think once the companion flange is torqued to specs it jams the distance piece between the center races of the two bearings so any exess space would need to be filled with added spacers. Also when replacing the bearings the book says to stuff the housing full of grease.  Does anyone think it would be overkill to drill and tap the housing for a grease fitting while I have it out?  I had bought new axel bearings for the 240 many years ago but never installed them. They appear to be the same dimensionally as the ones off the 280 27 spline piece. New bearings have more than doubled in price so I would really like to use them as they were made in Japan back then. Any comments to any of this will be appreciated.

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I don't know anything about the ZX axles, but I can provide a little input about greasing.

I think a zerk would be overkill, and I found from experience that you can actually over-grease the housing. First time I did bearings, I packed the entire inside of the housing with grease. I even used a long needle and injected grease into the recess after the whole thing was together until it oozed out from between the bearing balls. It was "stuffed full". Completely full. It was a mistake.

It was very very stiff and hard to rotate. So stiff, in fact, that I ended up taking it apart again and removing most of the grease. If you look at the amount of grease they put in there originally, you'll see that they didn't "stuff the housing full" of grease. I don't know if my experience is typical, but I packed the balls and added a little more for good measure and called it a day.

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The distance piece is supposed to match the bearing race in the hub.  Its purpose is to match the inner race distance with the outer race distance, of the ball bearing assemblies.  Described in the RA chapter, I think.  Letters are stamped on the piece and the hub and should match.  There's also a table showing specifications.  Attached the 1982 chart.

Distance Piece.PNG

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Thanks guys.  I will have to agree about the zerk fitting. I guess if my old z bearings lasted as long as they did with no added grease the new ones should out last me and any mileage I will put on the car.  A good hi speed moly should do the trick.  Also thanks for the info on the distance pieces I will look for the stamped mark and see what I have.  Thanks

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