Just wanted to get a discussion started on this topic. I know there is a small weight savings and some gains with inertia also with aluminum? So for most street/strip cars under 600 Hp, what type of advantages/disadvantages do you see? What type of 60', 1/8 mile and 1/4 mile gains for our 3500-4000 pound cars?
There is basically a $100 difference aluminum will be 3.5in steel will be 3in or in extreme duty cases 3.5 I run aluminum in our stuff Difference in performance is minimal but there nonetheless
I put one on my GS years ago and seem to remember .05 ET knocked off my wasn't done same day. It all adds up.... I was told that they have to be replaced after many runs and/or time interval and I did get another one made but unless 800+hp or transbrake I really don't see why. Many new vehicles use them and don't think they are being replaced at some interval. Only issue is that you must step up diameter and that can sometimes cause clearance issue with driveshaft loop.
I've been reading 0.05 to 0.1 second in the quarter mile. That's like trying to take off 50 to 100 pounds of dead weight off your car.... about 100 pounds for every 0.1 second. So even though aluminum doesn't weigh all that much less on a scale, the engine isn't using as much Hp to turn it and much of the savings is in the rotational energy, is my understanding. I also heard a general 1 Hp for every 10 pounds removed. If that's correct, as well as the 100 pounds for every 0.1 second, then conservatively, 0.05 seconds is like taking 50 pounds off or adding 5 HP. For only $100 more, that's $20 per HP, which makes sense economically.
And they look cool!! Haha. I run an aluminum driveshaft on the green car, pretty much for the reasons listed above. Wasn't much more money for some savings, however small. I've spent more on areas where less gains were to be had.
Along with the drive shaft loop clearance, if your exhaust system is already installed with an X or H pipe I would check for proper clearance if changing shaft diameter. My stystem was tucked up a little to high and had to modify my H pipe because when the rear suspension was unloaded it was resting on the pipe.
My timing couldn't be better. New exhaust sitting in the garage in a box now. New torque converter from Jim Weise just installed Friday, which lead to the discovery of a bent transmission crossmemember and driveshaft that is 2" short..... ugh. At the same time, glad I waited on the exhaust project. Dodged a bullet there. So I have to modify or put in a new driveshaft. Thinking new aluminum.... It's only 0.05..... that's true, but if I dismiss it for every mod, I'll lose a half second or more by the time all my projects are done.
Not as long as you account for it when installing, it's only 1/4in more clearance needed than your standard 3in shaft
You'd gain alot more by removing your spare,the jack and such from the trunk.I have a steel Driveshaft Specialties steel unit he warranteed to 900 hp. It was 100 bucks cheaper than an aluminum one. He talked me out of an aluminum one,but I am happy with mine as it also have 1350 U joints on each end.
isn't there some formula out there for rotational weight. i believe something like every pound of roatating weight is equal to 4 normal pounds when launching the car?
Just had an aluminum shaft made locally. Waiting on a cam and torque converter from JW so I haven't installed yet. The aluminum one is 3.5" vs the 3" steel. I weighed the 2 for comparison. The aluminum one weighs .3lbs less, BUT, the slip yoke is NOT on the steel shaft anymore, both shafts are the same length. I went aluminum just because the original was all rusty and nasty.
I regret that I didn't weigh the steel shaft and the Aluminum shaft, but just from lifting them I'll bet that the Aluminum shaft is at least six or seven pounds lighter then the steel one. The steel shaft didn't make the move to Florida with us, so I can't weigh it now.
Seems pretty close to some weight differences I read about chevelles. Now, how does that dead weight translate to rotational force? Because paying an extra $100 to save 7 pounds of dead weight is pretty expensive. Now tack on the power gained from rotational force savings and it starts looking better, correct?
Interesting read here: https://www.w8ji.com/rotating_mass_acceleration.htm Drive Shaft Example Now let's think about a drive shaft. The driveshaft is a fairly thin hollow tube. Nearly all drive shaft weight is at the outside, since it is (of course) hollow. The shaft also turns at the same RPM no matter what the driveshaft diameter, because the RPM is set by the rear end ratio, tire diameter, and vehicle speed. If we make a driveshaft lighter and keep everything else the same, the vehicle acceleration change is often insignificant. Why would it be insignificant in most cases? In the first place, the drive shaft is small in diameter. With a small diameter, less energy is stored for a given weight. In the second place, a driveshaft is really not that heavy. A steel Mustang driveshaft weighs somewhere around 30 pounds, so we just can't take that much weight out. Also, the driveshaft spins up gradually and smoothly over a long period of time. It accelerates fastest at slowest speeds, and that is when it needs the least energy to spin up. Because it has a long time to spin up, is a small diameter, and because it does not weigh much, the driveshaft does not remove very much horsepower at any instant of time. Despite what we are told, a change in driveshaft weight has, at best, a very small effect on acceleration. Likely any change is immeasurable in a street/strip car. Now a lighter shaft certainly can help in a very light vehicle. It can also help in a road race car (as will a light crank and flywheel), because road racing requires instantly changing from acceleration to deceleration. A light driveshaft won't change anything significant or measureable in a 3000-pound 11-second car, except how fast dollars leave your wallet! Another worry is driveshaft diameter. If we go from a 30-pound 3-inch steel driveshaft to a 30-pound 3.5-inch aluminum shaft, we move the weight out 3.5/3 = 1.167 times. That increases stored energy 1.167^2 times, or 1.36 times. If we store 0.3 horsepower in the shaft, changing the diameter will increase that to 0.4 horsepower. We would have to reduce weight 14.3% to 25.7 pounds just to break even with the diameter increase. The worst thing about a driveshaft is the diameter is so small, and the acceleration time is so long, there just isn't much horsepower being sapped from the system. A typical steel driveshaft in a typical 12 or 13 second car only stores an average of about 1/4 horsepower. If we got 100% of that back with a zero weight shaft, we would never notice it. Good reasons to change a driveshaft are to get rid of vibration and harmonic resonances in the shaft, to make it stronger, or to simplify a two-piece driveshaft system. The silliest reason is to speed the car up. Even if we only pay $100 for a shaft, it would typically be much less than 1/4-horsepower average gain. That would be paying much more than 100/.25 = $400 per horsepower. Paying a lot more than $400 per horsepower is not a good investment.
What type of u-joint straps you going to have on the rear end ? I had hex cap screws with my 3-inch and they were a pain. Had to use a ball-type wrench and there was only a certain are I could tighten or loosen the bolts.
