Harmonic Resonance/vibration question

[NoHaveMSG]

Originally Posted by new2subaru

What is the tape supposed to accomplish? I’ve seen a video of a guy balancing a driveshaft with hoseclamps.

It appears that the shaft has been balanced. There’s a few weights glued on it. FWIW, I think the one piece shaft delivers all kinds of vibrations from the rear. It makes sense not having the carrier bushing.

I did notice when I switched track tires that it lessened. It’s still there but not as profound. That or I’m getting used to it lol

Something about dampening a certain frequency range. I don't exactly remember.

[new2subaru]

Originally Posted by NoHaveMSG

Something about dampening a certain frequency range. I don't exactly remember.

Interesting. Vibrations are a waste of energy and destroy shit.

[Goingnowherefast]

Originally Posted by NoHaveMSG

Something about dampening a certain frequency range. I don't exactly remember.

Damping*

Dampening is when you're getting something wet

[why?]

Originally Posted by prandelia

Yeah, that is interesting, and comforting at the same time. It is also worth noting that I have SPL solid subframe bushings, and we "raised" the subframe about 0.5" toward the body (to allow for better axle angles after lowering the car), and this also slightly affects the drive angles. Nothing extreme, but it seems it may be more related simply to the AL construction than anything else, given others also note the same vibration.

The easy way to find out is to slap my OE drive shaft back in, and if it goes away, then we have our answer. Perhaps CF driveshaft would be better.

I bought my AL one locally for only $200 so couldn't resist it, so it's not a huge deal if I move away from it. It definitely felt like more of a "whole car" vibration, and while I've felt engine harmonics that bad, I can see how it might be the AL driveshaft as well.

Anybody with CF driveshafts notice anything similar?

I've seen lots of people on here with AL shafts that complain. Not as many with CF. I have a carbon one from driveshaft shops and I have a tiny increase in whine, but no added vibrations. I've had it in for about 20,000 miles so far. Note at this point my car is mostly stripped.

[Dzmitry]

So if it is the driveshaft, then it certainly sounds like an imbalance. I don't know where you can take it to get it balanced, but that would certainly solve your problem if it IS in fact the driveshaft and you would like to hold on to it.

Some interesting instructions to finding if you have an imbalanced driveshaft I found here. I would be far too lazy to do this though I guess in your situation it's basically impossible anyway, as you only experience it at higher RPM's.
http://www.demandaam.com/technical-s...haft-balancing

[CrowsFeast]

Since it's always around 5500 RPM in any gear, wouldn't it make sense for it to be something on the engine side of the transmission rather than the driveshaft?

[NoHaveMSG]

Originally Posted by Goingnowherefast

Damping*

Dampening is when you're getting something wet

Brain fart

Since it's always around 5500 RPM in any gear, wouldn't it make sense for it to be something on the engine side of the transmission rather than the driveshaft?

Can't speak for the OP but mine does it in other areas too, it is the worst at 5500. Similar to the OP mine is worse in upper gears.

I have read in other threads that balancing didn't help.

[ka-t_240]

Originally Posted by prandelia

Yeah, that is interesting, and comforting at the same time. It is also worth noting that I have SPL solid subframe bushings, and we "raised" the subframe about 0.5" toward the body (to allow for better axle angles after lowering the car), and this also slightly affects the drive angles. Nothing extreme, but it seems it may be more related simply to the AL construction than anything else, given others also note the same vibration.

How did you adjust the subframe?

[prandelia]

Originally Posted by ka-t_240

How did you adjust the subframe?

SPL's kit has shims, so you can install at OE height, or raise/lower it depending on what you want to do. Super easy to adjust.

[prandelia]

How many out there with CF driveshafts have vibrations ?

[new2subaru]

Originally Posted by prandelia

How many out there with CF driveshafts have vibrations ?

1

I’m not done tweaking it yet. I want to check the pinion angles. My rear is dropped slightly with bushing inserts and diff inserts. I don’t know if that threw it off.

[prandelia]

Originally Posted by new2subaru

1

I’m not done tweaking it yet. I want to check the pinion angles. My rear is dropped slightly with bushing inserts and diff inserts. I don’t know if that threw it off.

Which one do you have? PST, DSS, or Verus ?

I'm beginning to think if you have stiffer motor, trans, and diff mounts, typical of a race car, then virtually any 1 piece drive-shaft will vibrate badly. Maybe I'm wrong.

[StraightOuttaCanadaEh]

How bad are these vibrations? I have vibrations and/or resonance from either one, or a combination of, subframe and diff bushings, shifter bushing and trans insert and I really don't mind them. It makes the car sound raw and visceral. So how would a carbon driveshaft worsen the vibrations? Any insight on this? I wonder if anyone's done it in the same order

[Dzmitry]

Originally Posted by prandelia

Which one do you have? PST, DSS, or Verus ?

I'm beginning to think if you have stiffer motor, trans, and diff mounts, typical of a race car, then virtually any 1 piece drive-shaft will vibrate badly. Maybe I'm wrong.

What you said there is probably very true. As the motor and trans have natural vibrations, having mounts on them sends it to the rest of the chassis and parts. In this case, your driveshaft would certainly gain some substantial vibration, and not due to an imbalance (which makes more sense, not sure why I didn't think of that before).