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Roadster IRS Axle Half shaft Length Issue Poll

  • STD Width IRS NO axle length Issues

    Votes: 13 41.9%
  • STD Width IRS with axle length Issues

    Votes: 5 16.1%
  • PIN Width IRS with NO axle length Issues

    Votes: 10 32.3%
  • PIN Width IRS with axle length Issues

    Votes: 3 9.7%
  • IRS Other Issues

    Votes: 0 0.0%
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Baghdad Bob
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Discussion Starter #1
Trying to collect info on how big (or small) this issue is.
 

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Baghdad Bob
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866 Posts
Discussion Starter #3
I have been following these IRS issue posts for years. Still putting my MKIV together, it was delivered in July 2010.

If there was a range of dates that FF would fess up to supplying the short shafts that would be great, but i dont see anyone getting that answer as yet.

It is also unclear who at FFR, is the expert on the IRS issues. Since my iRS is all together and I am still working on the build, I would like to knwo if they are ok, AND of the clips in the diff are actually engaged.

I cannot feel the trilobes under the boot, so I may be ok.

How did you get the info that your kit fell into a range of production run dates that had short shafts ?
 

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Junior Charter Member
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1,223 Posts
STD Width IRS NO axle length Issues

My kit is from 2005. Back then we read about heat treat problems leading to axle failure. I've been on the road for 2 years, 5000 miles, 560 lb.ft. torque, no issues.
 

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Mine was delivered in March of 2012 and I had the issue. FFR’s fix was to send out spacers to fit on the outboard end of the axle between the inner hub bearing and the outer CV joint. I didn’t like their solution so purchased the new longer axles. I still have the shorter axles with CV joints and spacers if anyone is interested.

Bill Lomenick
 

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Baghdad Bob
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866 Posts
Discussion Starter #8
I am wondering how many IRS kits were sold. I may need to call FFR to find out.
 

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Junior Charter Member
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I have a MKIII with IRS. Used the rear hubs and diff from an 89 TurboCoupe. Used the F5 axles and have had no problems in the three years that I have been driving it, approx. 5,000 mi.
 

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I have one of the last MK3 kits with the pin drive IRS. I’m running the third member and hubs out of an 89 MK8. Have no issues with the axle length and the “C” clips fit normally in their slots.
Hope this helps with the research.
 

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From my research and speaking with FFR, ALL IRS half shafts supplied by them since they starting supplying half shafts with the irs option or complete kit, until shortly after they announced the issue, made the shaft design change and sent out spacers - are suspect.

So approx. 2008 - 2013? There's no definite/detailed tracking, and due to tolerance stack up, the only way to tell if you have the issue is to test, measure and inspect.

If you have shafts supplied by another vendor or 'donor' shafts, you probably or may not have an issue.

This is a shaft length design issue. The design fix was to lengthen the shaft. Thus you can assume all IRS half-shafts from FFR have the 'too short' shaft. This is not something that would be hit and miss (some are short and some are OK)

This isn't a manufacturing mistake.
 

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Does anyone have the information on what the correct length should be for both standard and pin drive?

In other words:
If you have pin drive width, your IRS shaft should be x" long.
If you have standard width, your IRS shaft should be y" long.

Clearly this would only help those whose half shafts have not yet been installed. However, it would be helpful to some if that information is available.

Perhaps anyway...

Regards,

Steve
 

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Baghdad Bob
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Discussion Starter #14
Thanks for all the feedback guys, looks like about 25% of pin drive and non pin drive have shaft length issues, so far !
 

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Baghdad Bob
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866 Posts
Discussion Starter #15
If my math is correct:

17/32 = 34/64
+
1/64 = 35/64

just slightly more tha a half inch !
 
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