Min spline length?

BJ_buggyfab

BJ_buggyfab

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Any one have a good answer to how little axle spline can be ran safely?

Back story.. I broke a cv star over Turkey day weekend. Cv cracked and splines stripped requiring the tow strap. After cleaning up the cv back home I’m wondering if it failed due to lack of sufficient spline in the star? I’ve ran this pair of axles 5 seasons with out an issue but just upgraded to more HP so I’m questioning why did it fail!?Just worn out ? Overdue?  I have had at least 8 seasons on these if not more   

best I can remember it’s about 2.5” of spline. 

E5A8788B-ABD3-48CC-85F3-7AB2874D2892.jpeg

 
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Midboard or stub?  I have 930's with midboards & they go all the way through both. I would guess it depends on HP.  if it was my car... "all the way through" would be the correct answer.

 
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L.R.S. said:
The star cracked and expanded then the axle spun inside tearing up the splines. 
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Right but closer look shows about 1/4” of spline was untouched? Makes me think the splines are short

 
Bobalos said:
Midboard or stub?  I have 930's with midboards & they go all the way through both. I would guess it depends on HP.  if it was my car... "all the way through" would be the correct answer.
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Microstub. 

 
You dont need much spline,  

Push the Axle all the way in pull the CV Star out and that will tell you what spline is being used, I think they can get down to 2.750'' or 3'' something like that, 

 
BJ_buggyfab said:
Right but closer look shows about 1/4” of spline was untouched? Makes me think the splines are short
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In the pic is that the inside or outside of the star? For my theory to be correct it would have to be the outside, even though it's 'supposed' to be the inside (raised face is the inside, but it really doesn't matter). Was the spiral clip in place?

A few seasons ago I kept loosing the spiral clip on the trans side with my mid-board 934 hubs. Found out I had used a 35 spline spiral clip but had 33 spline axles. My fault. Tore up a few CVs before figuring that one out. Prepped the car with my spare axles and found they were 1/2" short at full extension. The axle was only in the star about halfway. I shortened limit straps to get me through the season on my spares. Prepped the car again and pulled the shocks, cycled the trailing arms and got the correct length 36" axles from @parker@gearone.

 
you might need a longer axel. was that the trans side if so did the clip come off and the axel slid out to far.

 
The shortest I recommend is 3"

Measure to make sure you axle length is correct. 

assemble everything dry with no boots cycle your suspension and see what happens

also make sure you are running spiralox clips on both ends of the axle.

 
Agree: axle looks like it might be short, but all sorts of bad juju happens when you blow up a star like that.  Reassemble with circlips on both ends, fully droop it and make sure you still some slop in the axle shaft.  If you can't move the axle shaft, it's too short.

 
L.R.S. said:
In the pic is that the inside or outside of the star? For my theory to be correct it would have to be the outside, even though it's 'supposed' to be the inside (raised face is the inside, but it really doesn't matter). Was the spiral clip in place?

A few seasons ago I kept loosing the spiral clip on the trans side with my mid-board 934 hubs. Found out I had used a 35 spline spiral clip but had 33 spline axles. My fault. Tore up a few CVs before figuring that one out. Prepped the car with my spare axles and found they were 1/2" short at full extension. The axle was only in the star about halfway. I shortened limit straps to get me through the season on my spares. Prepped the car again and pulled the shocks, cycled the trailing arms and got the correct length 36" axles from @parker@gearone.
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Yes the raised part was the inside of the cv star. Spiral lock was in place and undamaged. This is why I question the spline length. 

 
Rockwood said:
Agree: axle looks like it might be short, but all sorts of bad juju happens when you blow up a star like that.  Reassemble with circlips on both ends, fully droop it and make sure you still some slop in the axle shaft.  If you can't move the axle shaft, it's too short.
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Rockwood said:
Agree: axle looks like it might be short, but all sorts of bad juju happens when you blow up a star like that.  Reassemble with circlips on both ends, fully droop it and make sure you still some slop in the axle shaft.  If you can't move the axle shaft, it's too short.
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I’ve done this. Axle has play at full droop. The spline length is the concern not overall axle length. I have about 2.5” of spline 

 
Jersey_Jeff73 said:
you might need a longer axel. was that the trans side if so did the clip come off and the axel slid out to far.
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Wheel side. Spiral lock was intact with no damage. I’m thinking longer spline amount may be best. 

 
BJ_buggyfab said:
I’ve done this. Axle has play at full droop. The spline length is the concern not overall axle length. I have about 2.5” of spline 
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Ah, I see it now: star slid inwards onto the non-splined area.  :doh:

Might be the case, but is there any spot in the travel where you have ~2" of axle plunge?

 
Rockwood said:
Ah, I see it now: star slid inwards onto the non-splined area.  :doh:

Might be the case, but is there any spot in the travel where you have ~2" of axle plunge?
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I guess possibly when axle is level would be most likely amount of chance as the axle can slide into the cup. It did break while under hard accel on level ground making me think the axle was near level then. I guess I need to do some more checking at different places in the travel. 

 
When the axle is completely level, you should only have about 1/2 of movement, and push the axle all the way towards the cup and pull out the star all the way from the cup, this will show you how much spline you will need,  

 
Any chance anyone has a set of 25” axles laying around? 😖

 
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