I've noticed most the companies that make a replacement drive shaft use a 2 pc. style. They also only have one section aluminum and one cromoly.
What is the reason behind keeping cromoly? Could you run 1 aluminum piece?
I would think the rotational weight would be greatly effected with a 1 pc.

 

http://www.awdmotorsports.com/index....mart&Itemid=29

 

Thats a 2 piece, replaces the rear 2 section and retains the stock front shaft

 

you can only run these shafts if you have solid mounted engine, gearbox and rear diff
the multiple pieces allow for movement, especially the 3 piece stock unit. Something to think about

 

not to say you are wrong, i'm no drive shaft wizard... but i have seen cars stand on end and trucks crawl rocks bigger then they were... all with 1 piece shafts. wouldnt a appropriately designed shaft with proper u joints on either end be able to handle it?

hell my work truck has 8x8 4 axles 4wheel steering and 2000 pound of torque... and all 4 axles use 1 piece shafts well unless you count that they extend and contract as a second piece... they still only have the joint at the tcase and diff

 

I thought about it more and saw flaws in the idea. You would need a slip joint like RSmike said. Looks like a two piece will have to do.

 

evo is only car on planet that has output shaft that moves up and down with engine torque. all other cars have engines that apply torque in a twisting motion to the shaft. thats why evo shafts are three piece.

 

There was a Federally mandated recall on first generation AWD DSMs due to the loss of transfer case fluid. The DSMs used an identical drive shaft to that on a EVO.

When the engine is torqued, the transfer case output shaft not only moves up and down but fore and aft. So, the drive shaft needs to be able to change it's length. In the case of DSM's, this adjustment wasn't adequate (the engine moved too much) and the transfer case output shaft pistoned the seal out of the first U-joint. With loss of fluid, the transfer case would suddenly lock, perhaps leading to an accident.

So, as posted above, the engine needs to be bolted solid for a one piece drive shaft to work.

 

A one piece will not work due to harmonics, as well as the movement issues.

The driveshaft is too long, you would overcome the critical speed with anything but like a 4" diameter aluminum shaft, and good luck fitting that. The EVO driveline is a LOT longer then most RWD driveshafts.

You could potentially do a 3" carbon driveshaft that was one piece if you had solid motor/trans/diff mounts. It might be able to get the critical speed high enough to not cause issues anyway.

 

How much power are you really losing with a two piece anyways? Not worth the hassle unless it's all solid mounts but for a daily driver eff that.

 

does anyone know what ams tuning runs in there 8-9 sec quarter beast with 1100hp?

 

AMS runs their aluminum driveshaft

 

dont believe this true either. I made one piece shaft for one of my cars. its steel ~3 inch diameter. it has no harmonic issues. there were many factory american cars with long one piece shafts. I had the shaft made from one. just welded on dsm ends and had it balanced.

 

Would you like to see the simple formula for resonance in a rotating shaft?

It's not magic and has lots of sound and well proven engineering principle and data behind it...

 

I dont want to see the formula. But maybe you could show it to the OEM guys who endangered lives by putting such a shaft on a production car?

I am more of a "try it to see if it works" or a "tweak something that is already known to work" kinda guy. I dont get hung up formulas that may not cover all the angles. Simple changes in pipe thickness and material is likely where you are in error with your theories. The one piece shaft I have here is very heavy. no lighter than a nice two piece shaft.