Quick question about driveshaft harmonics...

[IJ.]

And for those of us with 1-piece aluminum shafts, try to keep it under 140mph!

I'd say Critical is well under that Tek
(Your shaft supplier should be able to give you detailed specs on this)

If not here's a Calculator (not sure how accurate it is)

 

[Mr.PFloyd]

My brothers 1jz car recently got a 1 piece driveshaft.... the cars powerband is silky smooth now, and throttle response is as good as it gets.... But i told him to stick with the steel, and he did.

 

[supraguy@aol]

Great.
Me with my aluminum driveshaft, wondering if I'll get smacked in the balls one day with a big metal stick. I have one driveshaft loop, which I was planning on putting towards the front of the driveshaft, I think I might put a second towards the center, where the carrier bearing bolts in, so that If it splits either by the front yoke, or shears in the center, it will be contained.

 

[suprabad]

I am pretty sure that the vibration will not be addressed by sound deadening material.

It's more of a matter of rotating mass and the length of the driveshaft.

When you split the driveshaft in half (as the stock unit is) you mitigate some of the vibration that is unavoidable with a 1 piece (and relativly long) driveshaft.

 

[IJ.]

Most shafts will have a cardboard tube inside to dampen out noise, sometimes they have rubber.

The issue really isn't the noise it's having a shaft go above the critical speed
and how long it will last if sustained.

Here is a perfect example of what can happen.

^^

 

[Dirgle]

Don't the 200mph MKIV's run one pieces? That's pretty crazy.

 

[Poodles]

last I knew they ran stock driveshafts...

 

[TurboStreetCar]

so whats the deal here? is there a lightweight alternative that wont grenade? or is stock as good as it gets?

maybe a one piece built to a specific thickness and diameter? :1zhelp:

 

[IJ.]

6500 rpm = 8666 rpm at the shaft on a r154 you guys need to either do the math or contact your shaft supplier to find out the critical speed of what they're suppling you.

Increase the motor rpm and the shaft speed goes up, where this all becomes a problem is if you run low diff gears the road speed for a given rpm comes down and can easily put you above critical.

Factor in most stock or near stock GTE's and 3.73's won't even get close to peak rpm in 5th so "should" be safe but again this depends on each shaft taking into account it's material/wall thickness/diameter/length.

All of this isn't something I'd chance as I value my life and is why I had the large diameter 2 piece made as I know I'll never be in the danger zone.

 

[suprabad]

I had the large diameter 2 piece made as I know I'll never be in the danger zone.

Care to share with us what size diameter? Material? U-joints?

This seems like a much smarter alternative to a one piece shaft.

 

[IJ.]

3" Steel 1350 1 ton Solid spicer Uni's

 

[Mr. Sinister]

3" Steel 1350 1 ton Solid spicer Uni's

Did you end up using a stock carrier bearing or an aftermarket one?

 

[suprabad]

Did you end up using a stock carrier bearing or an aftermarket one?

Good question. +1

 

[WhtMa71]

IJ already answered that question

Chunks: Yep the carrier is a new OEM one

Uni's are 1350 Solid hi impact units bigger diameter heavy wall tube and a Spicer a340/r154> 1350 slip yoke.

 

[garagefujimoto]

6500 rpm = 8666 rpm at the shaft on a r154

6500 in 5th gear?

I guess my 4.10 gears wouldn't matter as the rpm is pre-differential.

I also imagine it's a consistent ratio, so one can expect 10,665 rpm at 8,000 rpm flat out in gear 5.

 

[IJ.]

Evan: Correct it gets scary fast above 7500 with hefty OD %'s
(My old Tremec TKO was .68 od and this is why I went custom 2 piece)