Some "Groovy" Half Shafts - need advise

[John D.]

Re: Some "Groovy" Half Shafts - need advise

For $140 each for brand new assemblies with u-joints why nose around for used ones ? With used originals you'll lose the condition points for pitting or the coating used to hide the rust. With the new ones you may or may not lose an originality point on the tubing.

[Terry M.]

Re: Some "Groovy" Half Shafts - need advise

Here are a couple of photos of the "torsional" failure mode, incipient and complete. The pair on the bench, showing a pronounced twist, came off a slightly modified '67 L-89 on stock tires (sheer luck they were spotted before they failed), and the ones on the floor were on a '67 with a 540 Merlin and 8" slicks.

John,
How many revolutions has the shaft turned on those ones on the bench?
It looks like it might be more than 360* That is very ductile, if I am seeing the longitudinal line correctly.
Every system has a weak link. Spinning tires, if there is no wheel hop, is the least expensive. Move the failure to other pieces and fun can become VERY expensive.

[Joe L.]

Re: Some "Groovy" Half Shafts - need advise

Here are a couple of photos of the "torsional" failure mode, incipient and complete. The pair on the bench, showing a pronounced twist, came off a slightly modified '67 L-89 on stock tires (sheer luck they were spotted before they failed), and the ones on the floor were on a '67 with a 540 Merlin and 8" slicks.

John------



These shafts demonstrate the point I've made on many occasions that a Corvette driveline is not designed for the kind of power and torque levels that some folks want to build into their engines. In fact, assuming that the L-89 involved in the failure of one of the pair of shafts here was stock, it demonstrates that even original power can cause failures in the Corvette driveline.

There IS such a thing as too much power in a 63-82 Corvette. Modifying engines for high power and, especially, torque levels requires major modifications of the driveline-----the kind of modifications that most Corvette owners, including those that want to "upgrade" their engines, would be loathe to make.

[Chuck S.]

Re: Some "Groovy" Half Shafts - need advise

Here are a couple of photos of the "torsional" failure mode, incipient and complete. The pair on the bench, showing a pronounced twist, came off a slightly modified '67 L-89 on stock tires (sheer luck they were spotted before they failed), and the ones on the floor were on a '67 with a 540 Merlin and 8" slicks.

The shafts on the bench (left) are about what I would have expected...maybe a little more twisting before something broke or the vehicle became impossible to operate.

The shafts on the right are well beyond what I would have ever expected from a automobile.

Thanks for the lab pics, John.

[Stephen B.]

Re: Some "Groovy" Half Shafts - need advise

I appreciate everyone's advice.

[Keith L.]

Re: Some "Groovy" Half Shafts - need advise

Stephen, what diid you soak them in? Just acid or a rust removal product?

[Michael W.]

Re: Some "Groovy" Half Shafts - need advise

The shafts on the bench (left) are about what I would have expected...maybe a little more twisting before something broke or the vehicle became impossible to operate.

IIRC, the shafts on the left were from the late Jerry C's car. I have a picture of one of those shafts held next to it's replacement. I also vaguely remember some attempts to replicate the failure mode.

[John H.]

Re: Some "Groovy" Half Shafts - need advise

IIRC, the shafts on the left were from the late Jerry C's car. I have a picture of one of those shafts held next to it's replacement. I also vaguely remember some attempts to replicate the failure mode.

Yes, I recall (vividly) my attempt to do so on a return trip from Willy's.

[Stephen B.]

Re: Some "Groovy" Half Shafts - need advise

Ultra One Safest Rust Remover Isn't it ironic that "Safest" is in the name. I've used other similar products without these destructive results.

[Keith L.]

Re: Some "Groovy" Half Shafts - need advise

Thanks, I thought it might have just been acid. That is scarry that a product like that would do that. How long were they in there?

[Ken B.]

Re: Some "Groovy" Half Shafts - need advise

Joe...What kind of modification to the drive train are you refering too ? Just curious

[Joe L.]

Re: Some "Groovy" Half Shafts - need advise

Joe...What kind of modification to the drive train are you refering too ? Just curious

Ken-----

Major upgrades to the third member, half shafts, u-joints, and trailing arms. Such modifications represent not only strength upgrade (the "good" part) but also a complete change in configuration (the "bad" part).

At major power upgrade levels, the only really "practical" thing to do is to remove the IRS and install a solid ("live") axle. More than a few Corvettes have gone this route (but NONE that would then do very well in NCRS or NCCB judging).

[Duke W.]

Re: Some "Groovy" Half Shafts - need advise

John------




There IS such a thing as too much power in a 63-82 Corvette. Modifying engines for high power and, especially, torque levels requires major modifications of the driveline-----.

It's torque that kills drivelines, including clutches, not power. A 5.5 liter engine that makes 500-600 HP will probably make no more than 400 lb-ft of torque. An 8 liter engine at that power level will make at least 600 lb-ft peak torque. Peak power is proportional to the product of revs and torque. Peak torque is a function of displacement and compression ratio, assuming natural aspiration.

Maximum engine output torque is the number needed to select clutches and transmissions along with maximum input speed, but behind the transmission peak torque is engine output torque times the lowest numerical gear ratio.

The above is why I prefer high revving small blocks. They don't put the driveline in jeopardy, regardless of how much power they make.


Duke

[Joe L.]

Re: Some "Groovy" Half Shafts - need advise

It's torque that kills drivelines, including clutches, not power. A 5.5 liter engine that makes 500-600 HP will probably make no more than 400 lb-ft of torque. An 8 liter engine at that power level will make at least 600 lb-ft peak torque. Peak power is proportional to the product of revs and torque. Peak torque is a function of displacement and compression ratio, assuming natural aspiration.

Maximum engine output torque is the number needed to select clutches and transmissions along with maximum input speed, but behind the transmission peak torque is engine output torque times the lowest numerical gear ratio.

The above is why I prefer high revving small blocks. They don't put the driveline in jeopardy, regardless of how much power they make.


Duke

Duke-----


.....and the driveline for 63-82 Corvettes was designed around small block torque and power, not big block. The driveline was not significantly upgraded in 1965 or later when big blocks were added to the Corvette engine choices. However, it's very possible to exceed the driveline capabilities of a 63-82 Corvette with a small block, too. Not the small blocks of the 60's, but the small blocks that are commonly built today.

[Stephen B.]

Re: Some "Groovy" Half Shafts - need advise

Keith,

I soaked them for about month which is obviously too long. However, I've soaked other parts for extended periods of time in solutions that were considered more caustic without any problems. It appears that the solution started to separate, and much of the active ingredients started floating on the water portion. Evidentially the active ingredients were stronger at the top of the solution, and it ate beyond the rust and into the metal.