smokeshow

iTrader: (16)

I did look up the modulus for each, and thats what I found as well. But the aluminum does have large diameter and thin walls to its advantage...

schino

iTrader: (14)

if you havent already check out this calculator http://www.supramania.com/forums/sho...d-A-Calculator i think we kind of talked about this before and we both have a 72" long 5" dia shaft. critical speed is about 6200rpm on that shaft. which for me is about a 150mph. i really didnt think this big thing would take that speed. and like you said a 3.5" one will only turn 3600 or so. this thought may save me some money because i was going to get a 2pc built. jake i cant remember if you were just looking at options or if you needed a shorter one or something. i may need one a little shorter for the 4l80 and being lowered and i found that my bosses 03ish 2500hd with allison crew cab short bed has a 70.5" driveshaft with 1410 u joints. just like ours but nearly 5" the full length not stepped down at the ends

smokeshow

iTrader: (16)

I will get a new drive shaft eventually, but it'll wait til the 370/80e. My concern is the speeds I'll be seeing at the track. Just trying to figure out if the nasty reputation that these new aluminum shafts have is a fluke, or is actually something worth worrying about. Like I said I've taken mine to 115 before. But my slicks are a little smaller, so the rpm I was turning then I'll most likely pass with the slicks.

schino

iTrader: (14)

the built ones are just so damn expensive. looking at the calculations people who go from the big alum ones to smaller steel are really dropping their top speed. maybe it really is a balance issue from the factory. ill have to look if anyone around here can balance to 5k or so. also im not sure what kind of rpm you are turning or plan to turn but figure on being locked up in 3rd gear engine rpm will equal drive shaft speed. even if i do run smaller slicks which i think i will i wont be turning much if any past that

AKlowriderZ71

iTrader: (22)

Not when switching to a 2-piece shaft, which is what most do. When the shafts are half the length, the critical speed goes WAY up.

iamkeniff

iTrader: (16)

i put a BONE STOCK 2 peice driveshaft and where i had a vibration at 103 it no longer has a vibration all the way to 135. yalls choice, id rather a 2 peice over that 1 peice.


i say put a 2 peice if your going to run faster than 110. you'll never see over 120 in the 1/4 mile unless you turn it into a race truck.

smokeshow

iTrader: (16)

I may go with a 2 piece with the new engine and tranny. I do plan on running a 10.90 eventually, and dammit I am gonna get there in an ECSB lol. So that might push me a bit over 120. Overall though I just like the extra insurance a better drive shaft provides.

So let me get this straight with the guys that know...critical speed occurs at a certain rpm, right? Would that mean that it just gets dangerous at that rpm and keeps getting worse as rpms rise, or would it pass that critical speed and then become smooth again?

double047

iTrader: (15)

^^ Wondering the same thing actually.

brent5631

iTrader: (7)

Its kind of hard to pass that rpm when shaft is in to pieces. But thinking about it from a harmonics standpoint I believe it would get better when you pass that range.

Mud slinger

iTrader: (2)

What about shifting at 6200 rpm? Why don't these DS fail at lower speeds spinning high rpms? You always hear about them blowing up at 100+
I'm asking because I want to set my shifts up around 6000-6200, but don't want to grenade my ds.