Recently after rebuilding the 454 in my '72 I had an immediate rear thrust bearing failure which resulted in having to tear down the engine once again.
During the brief period in which I was able to drive it and break it in I was less than impressed with the increase in power that I had somehow anticipated from the rebuild. Consequently, this time around I made some "internal changes" within the engine while keeping it completely original looking from the outside.
I dyno'd the engine last week and was able to get 590 ft./lbs. of torque from it and 468 h.p. with the original carb and air cleaner ! While I am very pleased, I decided to freshen up my transmission and torque converter to ensure everything could handle the extra muscle. Not stopping there I naturally replaced the u-joints with some h.d. Spicer units and while doing so I noticed a strange mark on my main driveshaft tube.
It would appear that possibly sometime in the cars' earlier lifetime the emergency brake cable may have hung down loosely enough to make contact with the driveshaft tube. This is the only possible explanation I can come up with for this perfectly concentric line I found neatly "cut" into the surface of the driveshaft.
I carefully did a non-destructive test of the driveshaft tube and found the wall thickness to be very consistent at .187 inch (3/16") except at the point of the groove which is at .177 inch. The groove is almost 1/16 wide.

My question is this :
Is there any way of accurately predicting what such a wear mark may cause in terms of overall weakness to the tube under hard/heavy acceleration? In other words is the reduction of 10 one-thousandths of an inch going to cause a potential fail to occur under extreme loading or are these driveshafts built so beefy that it should be little or no concern?

Access to quality driveline shops in my area are limited and I have not had much luck finding someone sympathetic to my quest in repairing this one or manufacturing another to orig. specifications.

Any comments or advice would be greatly appreciated.

Thanks, Rick

 

for peace of mind, just replace it

http://willcoxcorvette.com/product_i...oducts_id=5402

 

I am suprised your stock driveshaft is that thick.... I had a custom 2.5" unit built for mine and the thickest they could make it using off the shelf yoke end caps was .095 I believe... This driveshaft was considerably heavier then my stock on..






FWIW, I had this new shaft built by Ft Wayne Clutch & Driveline for $206 shipped....that was fully assembled with solid 1330 spicers.

A little piece of mind goes a long way.... I've been a bunch of low 1.50 60's on it and so far, so good.....

 

Another vote for Ft Wayne Driveshaft. I have had them do numerous projects and nothing but praise here, quality work at great prices. Don't run it with that lathe cut around it. If it does let go it will cause all kinds of carnage to your car. I seen a Nova almost flip over when the front u joint let go on a first to second powershift and it ripped the differential out of the back of the car. $206 well spent.

 

Thanks for the replies !
I am inclined to replace it as well. From the few "experts" I have spoken to about this, apparently the original spec tubing has not been readily available for some time now. Most driveline shops would now use .083 wall thickness and derive extra strength from using different material and/or going to a slightly larger dia. tube size such as 2.5 or 3".
The problem with the latter is that it supposedly requires dropping the differential in order to slide the shaft in from the rear of the car - as there is insufficient clearance to put it back in the same way as the original due to its' size.
I will check into Ft. Wayne as it is nice to have some actual feedback from happy customers rather than picking some firm off the internet with which I have no first hand knowledge as to the quality of their work !

 

Before ordering a larger diameter shaft, take a long hard look at how tight your present one is in the tunnel. My Vette has very little clearance by the seat belt reinforcements.

 

This is true.... Mine is pretty tight on the passenger side of the tunnel with the 2.5" shaft... I have maybe 1/4" clearance between the shaft and the seat belt support frame. I "could" get a 2.75" shaft in there with some minor clearancing but.... I chose to stick with the 2.5".

Definitely measure it out before you order a shaft....Every car is different...

I still can't believe the stock shaft had that thick of wall thickness. I figured it was .060" or .083"...

I never had a problem with my stock shaft and went quite a few nigh 1.50 60's on it but....Once I built the rear end, I decided $200 was worth the peace of mind of not having a 40 year old shaft spinning under me at 130+ mph....


FYI.... Fort Wayne clutch also did my 3" x.095" half shafts with solid 1350 spicers...Those are holding up fine as well..... You can get all 3 shafts made from them for around $450 shipped...

 

Any competent welder could put a single stitch on that cut and it would be stronger than the original. I was very abusive to my original drive shaft and it never failed. I now have 1330 u-joints on a lighter chromemoly drive shaft.

 

regardless of the wall thickness, that groove will act like a stress point and it will be considerably weaker than the rest of the tube. when the tube flexes under load, it won't flex uniformly to absorb the torque. just like scoring a piece of glass before you break (i hate that word) it.

 

Every good welder I spoke to cautioned me against trying to put a bead over top of the groove that is worn into the surface of the tube as they said they felt it would not be as strong as the welds at the ends of the shaft which, at that location, is butted up against the shoulder of the solid yoke piece.

I am glad you guys told me about the clearance issues because so far many driveline shops wanted to steer me towards a 3" dia. tube which may not fit at all !!!