What are the differences between the 99 and 01 cobra axles, It seem that I read there were some differences between the two. I wasn't sure if it was the composite of the metal or the number of splines. Also, does anyone have an idea what the stock 99 axles can handle in horsepower? Also what will the Auburn handle in the h.p? Thanks again...
Rear Axles
- Thread starter 71stang99
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The 99's have 28 spline axles while the 01's have 31 spline. I'm not sure of the metal make up of the two but the 01's are said to be much stronger and haven't heard of any breakage of them. The 99's can't seem to handle the stock horsepower if you put slicks on them so just be careful. As soon as mine break I will be adding an Eaton Posi with the 2001 31 spline axles.
thats what I thought I heard, I was just wanting to make sure since I want to do the 4.10's and while I am paying for the gears I might as well get a rear end kit with the axles and defferential kit and have it all done at once.
The differences between the 99 & 01 is only the spline count in the diff. 99=28 spline, 01=31 spline.
The halfshafts are the same(except the spline count) but the halfshafts are the weakest point of the rearend. So if anyone is running drag radials or E/T Streets I suggest upgrading to GKN or Raxles halfshafts.
The halfshafts are the same(except the spline count) but the halfshafts are the weakest point of the rearend. So if anyone is running drag radials or E/T Streets I suggest upgrading to GKN or Raxles halfshafts.
How much are new half shafts? Can you run 31 splines in a 99 with the stock gears or 4:10's. If not what has to be changed
GKN & Raxles offer upgraded halfshafts in both 28 & 31 spline designs to go with the 99 & 01 cars. The spline count has nothing to do with it, it's the strength of the shaft itself. Call either one of those places and they'll set you up. Cost is ~$380/each.
I can't believe that you say spline count has nothing to do with it! Why do you think racers get rid of the 28 spline in favor of 31 or 33 spline axles?
Your talking about solid axles.
The half-shaft for the IRS never breaks where the splines are. The rest of the half-shaft, including the part that breaks, is the same on either 28 or 31 spline shafts.
The GKN half-shaft is totally different design and much stronger.
I am pretty sure the principals of an axle is the same whether it is inside a differential housing or not (like on the IRS). A 31 spline axle is typically of a larger diameter than a 28 spline axle for a given application therefore it has the "potential" to be stronger which is why 31 spline axle are sought after. Since the shaft is larger in diameter there are typically more splines on it and the splines tend to be a little larger than on the smaller shaft. This does help prevent spline sheering but more importantly the shaft is typically stronger because it is larger diameter. I guess since the stock 99 axles are breaking in locations other than the splines then the 28 spline count must not be an issue (yet). If an aftermarket shaft addresses these other weak areas on the axle but still have the same smaller diameter 28 spline end on it then I would guess the weak link on the aftermarket shaft would be in the spline area.
They usually snap on the in-board side off the outter CV joint. The link below shows some pictures of a broken axle.
Shaft
The third picture shows someone's finger on the part of the shaft with 28 or 31 splines. The rest of the shaft is the same.
Shaft
The third picture shows someone's finger on the part of the shaft with 28 or 31 splines. The rest of the shaft is the same.
I am well aware of stepping up to 31 splines as that is what I have done in the solid axle that is going in my car.
As MikeC pointed out I was referring to the IRS halfshaft failures, the failures have not(yet) occured at the spline end of the shafts but where MikeC mentioned. Sorry for the confusion.
Btw, I've heard of a few 01 owners breaking their halfshafts. I think the reason we hear less breakage with the 01 is that those owners learned from the 99 owners and upgraded before they broke.
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