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At what point are the factory 28 spline axles not strong enough? I have about 300rwhp with 1.7 60' times.
What is their breaking point?
In retrospect, I SHOULD have gone to 31 spines when I had my 4:10's put in.
 

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Well i am running an 8" 4:11 and 28 spline..
Have broken alot of things but not the axles. yet
 

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The Mustang is running 1.94 60's and I have already replaced both 28 axles due to spline twist. YMMV. I'll check it again during the winter break and if they start twisting again, we'll have to move to 31s.
 

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You will know when you have found the breaking point, the car will make a hard left turn as soon as you leave the line.
 

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In my opinion ... CKelly gave you the answer that'll keep you out of trouble....

Unless the car is obviously over powered...The way to tell you are at or over the danger point is paint a stripe on the length of the axles. Then pull them periodically to check. Once they start to show twist, past a inch or so - they'll start to look like a candy cane - its time to replace the axles or move up to some thing thicker, like 31 splines.

It is possible to get thicker axles in 28 spline too. In that case, if you see the actual splines have a twist to them, are no longer straight, then there is no question...it's time to upgrade.

Factory axles will twist along the entire length before breaking (usually?)..., it has to do with how the factory metal is tempered and the kind of steel it is made from. Most racing axels are stronger, but when they let go, its usually all or nothing. The break will shear like it was cut.

Most of us are a little tight fisted when it comes to replacing something that ain't broke. Most Axel replacment shops will require that you measure the axels to get the right length. Just saying you have a 19xx "wonder wagon" is not good enough for them. As most of us find out sooner or later, especailly with older cars - whats on the vin or what was supposed to be in the car from the factory, can be changed through the years and progression of owners and the quality of care they gave the car.

So, don't let the prospect of pulling the axels twice ( once to measure and order, then again to install them) keep you putting it off until something makes it a real priority. And have to do bodywork.


When you seriously abuse a stock axel, it'll 'give" a little - like a torsion bar - if it happens a lot, after a while, it won't twist back to the same place. Over time it'll start to take a 'set' in the direction of the stress...as it twists more and more it gets closer and closer to a point when it will not twist anymore...thats when it fractures.

<font size=-1>[ This Message was edited by: Beoweolf on 8/25/06 1:29am ]</font>
 

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Running 1.5-1.6 60ft times in a 3660 lb car with a traction-lok and have never seen a twist since 1983 when I got the car.
 

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If i wasn't lazy and tight, i would have upgraded mine by now. I have had the same set of std 28 splines in there for 10 years and that whole time it had a mini spool. For the last 6 months i have used MT streets on the street and full slicks with 1.70 60 footers on the strip in 3650 pound car, with no dramas. But i too dont want to wait for the break and possible crash.
 

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I have a best of 1.69 and MANY 1.7x 60 footers on my 28 spline axles in my '66 Stang. Nothing broken yet. And no twist either.
 

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You guys running STOCK 28 or 31 spline axles checkout this link.

http://www.torinocobra.com/my_repair.htm

After seeing it, I decided to upgrade to Moser 31 spline axles.

Since the axles were custom made, I also decided to narrow the rearend at the same time, but the main deal was to lose the factory axles.



Greg
 

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Much depends upon stickshift vs. automatic.

I've watched several STOCK 5-speed equipped 5.0 mustangs on sticky tires break the stock 28 spline axles. I've seen 28 spline axles behind automatics run into the 11's.

YMMV, but shockloads are a bitch, and stickshift cars need to upgrade right out of the box.

If you are buying a new differential, might as well make it a 31 spline and do it all at once.
 

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No, they wont fit the carrier. I had to just go this route!
 

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Moser makes stronger than stock 28 spline axles.
 

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On 2006-08-25 14:27, Tracer64 wrote:
No, they wont fit the carrier. I had to just go this route!
Do you mean they wont fit the side gears or the actual carrier?
I know they wouldn't fit the side gears since one is 28 spline and the new shafts would be 31 spline.

I was really asking if they fit through the axle flanges.

If they wont fit the carrier, what is the option? I have a detroit in mine and was under the impression that all you had to do was change out the side gears.
 

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From the way I was told and understand, small bearing 9" 28 spline axles will interchange with 8" 28 spline axles. When you go 31 or more, due to the smaller ring and pinion, they do not make 31 spline axles for the 8" due to not enough surface area in the side gears. Something to that effect.
Tracy
 

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On 2006-09-08 16:51, Tracer64 wrote:
From the way I was told and understand, small bearing 9" 28 spline axles will interchange with 8" 28 spline axles. When you go 31 or more, due to the smaller ring and pinion, they do not make 31 spline axles for the 8" due to not enough surface area in the side gears. Something to that effect.
Tracy
Yes, the 9" and 8" 28 spline axles are interchangeable. There really isn't anything to gain by adding 9" 28 spline axles to an 8" 28 spline rear.

You can't intall a 31 spline axle in an 8" housing. You would need to have 31 spline side gears for an open rear and a 31 spline carrier for a posi/limited slip rear. If you could, the weak point would still be where the axle was tapered down to make the splines to engage the differential. The overall axle would be just as weak as a 28 spline axle.
 
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