[DeTomaso] Techno Question: Stock half shafts torque tolerance

[MikeLDrew at aol.com]

In a message dated 6/15/12 7 03 51, cengles at cox.net writes:


>                 How much power or torque can one put through 40 year old
> stock half shafts?   Stock power only?  400 ft/lbs?  550 ft/lbs?
> 
>                 Would there be any reason not to upgrade to Spicer half
> shafts?
> 

>>>Spicer driveshafts are not an 'upgrade'.   In fact, it's possible the 
driveshafts themselves might even have less torque tolorence than the stock 
ones.

The only reason the vendors were pushing that idea was because of failures 
of stock driveshaft U-joints.   They were the weak link in the system, but 
the driveshafts themselves were fine.   Replacement U-joints used to cost a 
fortune, which helped make Spicer replacements more attractive as well.

For awhile, Hall Pantera modified (and I use that word kindly) stock 
driveshafts to accept generic USA U-joints.   Apparently they used some sort of 
adapter pressed into the driveshaft, and used a smaller-than-stock U-joint.   
History has since frowned on that modification and it's not done anymore, as 
the machining ruins the driveshaft for stock U-joint use.

For the past quite-a-few years though, stock replacement U-joints with much 
greater strength have been available cheaply from the vendors.   Some have 
reported that they were actually slightly modified Toyota 4x4 U-joints, 
although I don't think anybody has ever offered any proof of that, nor is there 
any suggestion that this is what they are still using today.   In any event, 
good U-joints for stock driveshafts (which are good) are available 
relatively cheaply.   I think the production of Spicer driveshafts for Panteras has 
all but ground to a halt in recent years.

FWIW, I have personally witnessed one Spicer driveshaft failure and recall 
at least one other, due to improper welding, where the end of the driveshaft 
(that holds the U-joint) broke away from the tubular portion of the shaft 
itself--thankfully at walking speed so there was no damage.   Meanwhile, I 
have never heard of a stock driveshaft failure (not including stock U-joint 
failure).

Dennis Quella told me years ago that the Pikes Peak buggy racers that he 
builds ZF gearboxes for, use stock driveshafts.   They put out so much power 
and hammer them so hard that they actually twist like licorice sticks, and he 
showed me one with about a measurable twist in it from such abuse.   

It did *not* break.

He said that what they would do is swap the driveshafts side-to-side 
between runs, so that it would twist once, then un-twist on the second run!   They 
would thus work these driveshafts again and again, but eventually would 
surrender them to the scrap heap.

Will you (or anyone) ever be able to impart a measurable twist into your 
driveshaft with your Pantera, even driving it as hard as you can on a track, 
with track tires?

No. :>)

Mike