Driveshaft on a DD FRS

[Chimpo]

Originally Posted by AJ PwR

I don't know if it is just me, I have the PST drive shaft. It's a quality built piece but I notice a vibration. It's acceptable at low rpm ranges but at 5th gear 4000rpm, you can feel it ! It vibrates though the seat then up to my butt. The feeling is like sitting on a message chair.

I installed a diff brace and that increased the vibration even more so I have to take it off. To ensure the diff brace is causing the vibration so I installed it to my friends BRZ and he doesn't get the vibration

I ended up put the stock one back on and the vibration went away ! I am not sure if it's me or my car or something to do with the shaft !

Does anyone has the same issue ?

Are you surprised that stiffening up the drivetrain made it worse? I remember my friend installed solid motor mounts on his Neon SRT4 and you could see the dash vibrating.

WIthout being there, it sounds like the prop was out of balance if it started when you installed it and it was fixed when you pulled it. Next time see if the vibration is there in multiple gears, not just 5th, as the vibration will be tied to vehicle speed and not transmission gear.

Also, you can fix an out of balance prop in a car. I doubt a dealer would do it for free since you have an aftermarket prop, but it can be easily done.

[Bullnettles]

Originally Posted by Chimpo

Power loss? I'm assuming your talking about the prop twisting under load, and that will be a property of the material it's made of and a "tiny" amount of slip in the center joint splines. *side note, I'm guessing on that, will look when done how this prop is put together* Look at a car with an IDS and equal length halfshafts. Obviously this is done to help mitigate torque steer induced by the a longer one piece design twisting more and esentially not allowing one wheel to keep up with the other (although there may be packaging / cost influences as well).

And any prop spun fast enough is eventually going to hit it's critical speed and potentially fail. That's not the fault of it being a two piece design, that's the fault of the operator being stupid by incorrect use or poor choice of tube diameter/thickness. On a side note, I've heard NASCAR goes through the critical speed of their props, but they go through it quickly enough (getting out of the natural freq range) that it's not a problem... plus it probably is replace after every race...

Don't misunderstand me, carbon fiber prop is choice and you'll see improvement, but there is nothing wrong with what came in your car either.

Oh, I'm not hating on the design, I understand it's that way for a reason, but any time you have a turn/joint, it will lose power. I've already had the car on high-speed runs, so not too worried about it, just wouldn't mind dropping the weight and getting a bit of power back.

[Adeets]

Originally Posted by AJ PwR

I don't know if it is just me, I have the PST drive shaft. It's a quality built piece but I notice a vibration. It's acceptable at low rpm ranges but at 5th gear 4000rpm, you can feel it ! It vibrates though the seat then up to my butt. The feeling is like sitting on a message chair.

I installed a diff brace and that increased the vibration even more so I have to take it off. To ensure the diff brace is causing the vibration so I installed it to my friends BRZ and he doesn't get the vibration

I ended up put the stock one back on and the vibration went away ! I am not sure if it's me or my car or something to do with the shaft !

Does anyone has the same issue ?

No I'm not noticing that the only reason I can tell its on my car any more is the slight honk when it unloads/loads up on power shifts.

[Lonewolf]

Originally Posted by OrbitalEllipses

That's not comforting, even if it's a "non-issue" I can't stand vibrations.

But women love them...

[OrbitalEllipses]

Originally Posted by Lonewolf

But women love them...

The vibrations here are different, not like Planet Earth.

[neutron256]

No vibrations here. My Driveshaft Shop shaft is if anything a little smoother then OEM as it should be.

[AJ PwR]

Originally Posted by Chimpo

Are you surprised that stiffening up the drivetrain made it worse? I remember my friend installed solid motor mounts on his Neon SRT4 and you could see the dash vibrating.

WIthout being there, it sounds like the prop was out of balance if it started when you installed it and it was fixed when you pulled it. Next time see if the vibration is there in multiple gears, not just 5th, as the vibration will be tied to vehicle speed and not transmission gear.

Also, you can fix an out of balance prop in a car. I doubt a dealer would do it for free since you have an aftermarket prop, but it can be easily done.

I used to have solid diff mounts and carbon prop shaft on my S2000 and it didn't vibrate that much but on the BRZ, it felt like 4 times the vibration with the diff brace with stock bushings.......so I ended up taking them off. The vibration feels like the wheels are off centric BAD !

[wootwoot]

I think that diff brace essentially makes the mount solid.... No wonder you had so much vibration. The whitleine inserts may be a good middle ground.

[Hardrock4445]

I'd get that shaft looked at/balanced. Local fleet pride?

[Laika]

Originally Posted by Bullnettles

Hmm, why would anyone go with the CF over the aluminum if weight savings are the same? Only thing I can think of if will the AL one not clear stock guards?

IIRC.... In the event of a failure, a carbon fiber DS is supposed to fall apart more gradually. The aluminum on the other hand gets obliterated quickly/violently.

[wootwoot]

Aluminum does better with impact. If you ran over something, for example, it would dent where the carbon fiber would snap.

[Bullnettles]

Aluminum D/S is installed, slight vibration. Going to turn it 90* tomorrow, along with the trans bushing being installed. It doesn't bother me too much, but the rear-view is now fuzzy at times, so wee'll see. Love the car with stickier tires and lighter unsprung weight, though. Can't wait for the trans bushing to really make it a solid transfer of power.

[OICU812]

Originally Posted by Bullnettles

Aluminum D/S is installed, slight vibration. Going to turn it 90* tomorrow, along with the trans bushing being installed. It doesn't bother me too much, but the rear-view is now fuzzy at times, so wee'll see. Love the car with stickier tires and lighter unsprung weight, though. Can't wait for the trans bushing to really make it a solid transfer of power.

Do you have a differential mount as well? Friend just installed his DSS Aliminum shaft and has a vibration that even after turning shaft all corners still has a vibration as well :/

Right in around 80mph+ the vibration becomes increasingly more pronounced.

[industrial]

Originally Posted by AJ PwR

I don't know if it is just me, I have the PST drive shaft. It's a quality built piece but I notice a vibration. It's acceptable at low rpm ranges but at 5th gear 4000rpm, you can feel it ! It vibrates though the seat then up to my butt. The feeling is like sitting on a message chair.

I installed a diff brace and that increased the vibration even more so I have to take it off. To ensure the diff brace is causing the vibration so I installed it to my friends BRZ and he doesn't get the vibration

I ended up put the stock one back on and the vibration went away ! I am not sure if it's me or my car or something to do with the shaft !

Does anyone has the same issue ?

Nothing like that with my axle-exchange aluminum driveshaft. I just have some drivetrain noise on decel at 3500-4000 rpm. No vibrations. Sounds like you got a bad shaft.