This is true as long as you are "ringing" like parts. In other words, a cast axle will not ring at as high a pitch, nor for as long, as a forged axle will. I have a row of crankshafts hanging in my shop, and a forged Mopar 440 crank rings at a higher pitch than the cast one hanging right next to it. But the smaller cast SBC 350 crank rings at a higher pitch than either of them. The size (and shape) of the ringing item has a lot to do with what it will sound like.
What ever happened to the cast aluminum dropped axles TCI had at their goodguise booth in the late '80s? I also heard someone else was selling them afterward, they were shown at the SEMA show, and a couple of GNRS 'High Profilers' had them. They received lots of fanfare, (as does any 'golden eagle' in the street rod circles...)
Saw a lot of alum axles on OTR tractors in the '70s, probably a product of the weight laws at the time and a thing of the past now. Super Bell lists aluminum I beam axles, even saw one on a car at Back to the '50's, seemed to go with the billet and stainless braid.
You all are aware that I was just being an *** right? On the original axle in the thread if I had to fathom a guess I would guess that it is a forged unit. That is not to say that someone didn't cast one that looks like that and it should be noticed that you cannot really tell once on has been polished and plated if it is cast or forged. I am basing my guess on the fact that it appears to be stretch droped and although it is not impossible it is improbable that a cast axle would have been done that way. All that said it is just a guess.
After mocking up the front suspension and wheels with the split bones on the outer frame rails, it became obvious that my turning radius was going to be terribly poor. So I tried several options to move the bones inboard, closer to the stock positions, but not quite. Here's what I ended up doing..... Now the tires have a much greater range of motion, turning radius is greatly improved.
Voodoo, Believe it or not that is a very old world solution. The radius rods running parallel to the frame rails looks cool but if you look through old photo albums from the old fellas way back when you see a lot of them with the radius rods canted in toward the center line. Splitting the bones was originally done to make a different engine that Henry didn't intend to go in there fit. it was a clearance thing. It should actually handle better that way then with the bones run parallel to the frame rails. Oh BTW I am working on the axle do you want the first cast aluminum one or do you want the painted carved wooden plug. I think the wooden one would be more old school.
Believe me, I know that I won't be blazing any new paths with anything that I do.....unless it's wrong! LOL.....yeah, put me down for the first aluminum axle. Need any old soda cans to melt down?
I worry about chromed (or any plated) parts in potentially high stress applications. hydrogen embrittlement http://books.google.com/books?id=kf...&resnum=2&ved=0CCkQ6AEwAQ#v=onepage&q&f=false
Well I woudn't tell any of the bazillion of rodders that have been running chromed suspension parts for the last 60+ years. They are ignorant of the fact and you know what they say ignorance is bliss. If you are not blazing any new paths you may just screw around and end up building a traditional rod. Tell you what you send the cans I have rethunk it and believe that pot metal might be a better bet on those axles.
My last build was a 33 ford pickup. I used a 34 frame, aftermarket Speedway "narrow" 32 style dropped axle with split bones attached just under the frame rails and 40 brakes with 35 ford wires and 6:00-16" tires...never had a contact issue between split bones and tires and that was with the narrow axle