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kroegarn

Stub axle wobble?

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I´m doing a rear end overhaul. Had a bad clonking noise which came from the rear diff, had the OBX diff overhauled and also tightened up the backlash a bit.

 

Second part up was the really bad vibration that showed up at speeds above 100 mph. Used a indicator dial at the adaptor plate for the 280 ZX Turbo drive axle, and it showed a difference of 1 mm. It was even possible to see the wobble with your own eyes. Removed the strut and using the indicator dial on the stub itself it wobbled a 1/10 of a millimeter on the left side, the right side was a lot better but not perfect. 

 

Is this something that is common? Will it happen again using the stock stub axles when trying out the surface grip with the 512 whp??  

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Could just be that the bearings need to be replaced.

 

Also, check the runout on the wheel mounting flange. The flange is soft and can be bent hitting a curb. A bent mounting flange would cause the wheel to wobble.

 

Of course, check all of the rotating assemblies such as the drive shaft, half-shafts etc.

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Edited by Miles

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I found a bent stub axle when I did a rear disc brake conversion.

 

Ditto RebkahsZ. Bent stub axles can cause problems.

 

I found that slightly bent stub axle flanges on my 240Z with 240SX rear calipers caused the pads to drag. Didn't catch it until I checked the run out on each stub axle flange. I had the flanges machined, but they were too far out.  I ended up buying the Chequered Flag stub axles and all has been well since. Remember the 240Z stub axles were designed to work with drum brakes so flange run out wasn't much of  a problem.

Edited by Miles

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Second part up was the really bad vibration that showed up at speeds above 100 mph. Used a indicator dial at the adaptor plate for the 280 ZX Turbo drive axle, and it showed a difference of 1 mm. It was even possible to see the wobble with your own eyes. Removed the strut and using the indicator dial on the stub itself it wobbled a 1/10 of a millimeter on the left side, the right side was a lot better but not perfect. 

 

Is this something that is common? Will it happen again using the stock stub axles when trying out the surface grip with the 512 whp??  

A few basics seem off here.  Looks like your dial indicator probe is sitting on the threads, and the shaft itself, alone, may not be what determines if the flanges run true.  When the axles and companion are bolted together things may be different.  Along with the bearing play.  Probably best to measure an assembled set.

 

100 mph doesn't really have anything to do with 512 whp.  You can get there with 150 probably.  Just saying, traction and torque cause different problems from high speed spinning.

 

Is the adaptor plate the same one that Miles shows in his link.  The Modern Motorsport 280ZXT adapter?

 

 

(Note to mods - I thought that I had posted on this earlier with a comment about quality.  If I did, and offended, please let me know.  I thought it was innocuous and relevant.  But maybe there's some sensitivity.  Or maybe I never hit Add Reply.  Not sure).

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Thanks guys for all your input!

 

I had the stub axles over to a friend of mine where we could put them up in his lathe. The stubs themselves are actually pretty straight and fine BUT the adaptor plates seems to be the culprit. Not sure if I can find any machine shop that can balance them, otherwise I´ll have to source myself a set of new ones. 

 

Regarding where they are from I actually don´t know, but they look like this (one is modified for the speed sensor): 

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As I understand things, the 240Z and 280ZX use the same diameter and spline count.  People swap in 280ZX axles for 240Z, by modifying the dust shield. The 280Z is different.  So the 280ZXT adapter might work.

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As I understand things, the 240Z and 280ZX use the same diameter and spline count.  People swap in 280ZX axles for 240Z, by modifying the dust shield. The 280Z is different.  So the 280ZXT adapter might work.

I was a bit unclear, but my stub axle only has 25 splines so buying the 27 spline adapter would also require the Chequered flag stub axle (or equivalent). 

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Id be willing to place a bet that your bad vibration above 100mph is a drive shaft problem. Balance/run out will cause a DS to vibrate like mad at high speeds, minor runout in the adaptor plates or axles/wheels will not so much. I had a bad vibration and too found run out on one of my adaptor/stub axles. Fixed the problem vibration remained. It ended up being a DS that was out of balance, even though I it had made and balanced at a shop it still vibrated on the car for whatever reason. I hose clamped a large washer to the DS and moved it around until the vibration disappeared. You can also try rotating the DS on the pinion flange. Throw a indicator on the DS as well and see how much it runs out. I had .001" of DS runout on the car, and rotating it on the flange did not fix my vibration. The only thing that did was hose clamping a large washer to it, exact opposite end of where the shop installed a balance weight. A Lot of these shops cannot spin their shafts past 3000rpm, and this is when my vibration begins. With 4.11 gearing the problem only gets worse.

 

Now I am not saying this IS your problem, but Its something to look over with a fine tooth comb.

Edited by 240zdan

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I have new 280ZXT adapters if you need a pair.Joe

I may call for a consult today. I have 27spline stubs with stock u-joint halfshafts. I detect some bearing play and I get nasty vibration on hard corners. (275 Hoosiers). Time to open these back up, check runout and consider CVs etc.

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I ended up ordering the stub axles and companion flanges from Chequered flag!! Now it´s all about waitiiiiiing for them to arrive and get that Z back on the ground! :)

 

You may already know this, use a locknut from a 280ZX instead of the stock nut. The 280ZX is self locking. The stock nut has to be peened against the axle shaft which makes future disassembly difficult. 

 

Also, make sure that the bearings and grease seasl are perfectly seated before tightening the lock nut.

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