Any reason not to use the fat diameter halfshaft?

Mike Puckett

SCCoA Member
Since my wheel bearings are 20 years old and are a bit noisy above 110mph I decided to swap out my rear halfshaft and knuckle assemblies with some much newer ones. The newest set that I have came out of a 94 SC automatic and both halfshafts are the smaller diameter shaft. I also have a set of 5 spd halfshafts that have the fat diameter shaft for the passenger side but are older with more miles on them. I'm also going to be building another motor that'll give me around 400hp at the wheels. I understand that the fat shaft is for reducing wheel hop and not strength. Is there, then, any real reason not to use the smaller shaft instead since it's a lot newer and is lighter than the fat shaft? Or would I be better off to use the fat shaft anyway.
 
Since my wheel bearings are 20 years old and are a bit noisy above 110mph I decided to swap out my rear halfshaft and knuckle assemblies with some much newer ones. The newest set that I have came out of a 94 SC automatic and both halfshafts are the smaller diameter shaft. I also have a set of 5 spd halfshafts that have the fat diameter shaft for the passenger side but are older with more miles on them. I'm also going to be building another motor that'll give me around 400hp at the wheels. I understand that the fat shaft is for reducing wheel hop and not strength. Is there, then, any real reason not to use the smaller shaft instead since it's a lot newer and is lighter than the fat shaft? Or would I be better off to use the fat shaft anyway.

I doubt that you'd notice the difference. Are the other shafts 1.2" in diameter?
 
If your going to be putting that kind of power to the rear wheels, I wouldn't worry about the FAT shaft as much as the pumpkin! I would Definately suggest putting your money into the pumpkin brace to keep the back from exploding. Just my opinion!
 
3 of the halfshafts are 1.2". Two are left side and one is right side. I've got more but they've been removed from the knuckles. The fat shaft is heavier as well so I'll save a little more weight. The pumpkin brace is a good idea and I think I'll add that along the way. I do run ET Streets at the dragstrip. I guess I can slways swap it back later if there is a problem.
 
Mike,

From what I've read you should use one skinny and one fat shaft. Something about the shafts having different natural harmonic frequencies because of their mass is what helps to reduce the wheel hop (not the weight of the shaft). Don't think it matters which side gets the fat one.

David
 
That's my understanding as well David. Is it really necessary or helpful, though. I get a little wheel hop now sometimes as it is. The reason I ask is that my two skinny ones are newer and have less wear on them. All of them turn smoothly but I can just barely feel that the fat one isn't quite as tight as the skinny one. The fat one has a lot more rust too. I'll use the newer one on the left side for sure but just wondered if I'd regret putting the skinny one on the right side.
 
That's my understanding as well David. Is it really necessary or helpful, though. I get a little wheel hop now sometimes as it is. The reason I ask is that my two skinny ones are newer and have less wear on them. All of them turn smoothly but I can just barely feel that the fat one isn't quite as tight as the skinny one. The fat one has a lot more rust too. I'll use the newer one on the left side for sure but just wondered if I'd regret putting the skinny one on the right side.

Mike,

If racing with a bias ply slick I don't think it will matter what shafts you use. I'd use whichever ones are in the best condition.

David
 
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