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Engine, Exhaust, Transmission Discuss the FR-S | 86 | BRZ engine, exhaust and drivetrain.


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Old 11-15-2021, 08:58 AM   #1
letmethefuqin
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Slapping / bouncing feeling when driving slow or changing gears

Be patient with me here,
Iím not to client about gearboxes

Ever since I swiped my clutch out it bunny hops like mad in every great change
At first I thought it was in the tune, but the tuner canít find an error (I have logs - Ecutek)

So looks to be mechanical
Iíll drive 10km 9í a straight road in 1st at about 2500
Very light pressure on the throttle and the car feels like itís driving but something slapping back and forth / bouncing

Canít figure out what is causing this any suggestions ?

Also before the gear box and clutch change the car always felt like it had a lightened fly wheel which it didnít, but I felt I had to previously keep the revs up, that seemed to work itís self out after a re tune though I feel

However in this case it feels possibly more mechanical

Anyone had something similar ?




2012 86 GTS
Heavy duty sprung clutch
Forged fork
Aftermarket pivot
Super pro rear?? Bush
Mtec springs
Motul oil

Rear diff bush compressors
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Old 11-15-2021, 09:14 AM   #2
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What make clutch?
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Old 11-15-2021, 04:31 PM   #3
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What you say, there, @Ultramaroon - ??
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Old 11-15-2021, 04:39 PM   #4
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I think @Tcoat's already asked the important question. If it's not a stock clutch, all bets are off.
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Old 11-15-2021, 08:07 PM   #5
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Quote:
Originally Posted by Ultramaroon View Post
I think @Tcoat's already asked the important question. If it's not a stock clutch, all bets are off.
Just Went and Checked,

It Appears to be a MANTIC Stage 1
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Old 11-15-2021, 08:25 PM   #6
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What condition is your trans mount in?
Stock one has a decent amount of slop and can cause bucking in the driveline.
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Old 11-15-2021, 09:07 PM   #7
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Quote:
Originally Posted by letmethefuqin View Post
Rear diff bush compressors
If you have the rear diff bushings but not the rest of the parts set in the "Positive Traction Kit" from whiteline, you might be getting more play in your rear crossmember and subframe bushings.

I essentially had that problem when I installed whiteline subframe inserts but didn't do the differential bushing until later, the diff was moving around a lot more from stiffening the other parts in the driveline and made it difficult to drive.

Also agree with above that you might be getting slop from the transmission bushing.
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Old 11-15-2021, 09:52 PM   #8
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Quote:
Originally Posted by letmethefuqin View Post
Ever since I swiped my clutch out it bunny hops like mad in every great change
This sounds to me like the new clutch is more aggressive than your old one and you need to adjust to it and possibly give it time to bed in also.


Quote:
Originally Posted by letmethefuqin View Post
Iíll drive 10km 9í a straight road in 1st at about 2500
Very light pressure on the throttle and the car feels like itís driving but something slapping back and forth / bouncing
This sounds like drivetrain slop. These cars had some even from brand new. How many kms has your car done? It may just need some bushes replaced.


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Originally Posted by letmethefuqin View Post
Also before the gear box and clutch change the car always felt like it had a lightened fly wheel which it didnít, but I felt I had to previously keep the revs up, that seemed to work itís self out after a re tune though I feel
Subaru motors have small, lightweight crankshafts and usually feel more like a lightened flywheel compared to a normal inline 4cyl engine.
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Old 11-16-2021, 12:14 AM   #9
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was the drive shaft removed at any point for any of this work?

was it clocked correctly?
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Old 11-16-2021, 08:40 AM   #10
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Quote:
Originally Posted by letmethefuqin View Post
Just Went and Checked,

It Appears to be a MANTIC Stage 1
Quote:
Originally Posted by Turdinator View Post
This sounds to me like the new clutch is more aggressive than your old one and you need to adjust to it and possibly give it time to bed in also.



This sounds like drivetrain slop. These cars had some even from brand new. How many kms has your car done? It may just need some bushes replaced.



Subaru motors have small, lightweight crankshafts and usually feel more like a lightened flywheel compared to a normal inline 4cyl engine.
Not familiar with that brand but a quick look shows that it is indeed quite aggressive. As Turd says you may need a bit longer "break in" period for it.

If that doesn't do it then like a few have said you could move onto bushings but the most probable cause is what you changed so start with the clutch itself and work back from there.
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Old 11-16-2021, 01:40 PM   #11
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The whole driveline is pretty squishy. Couple that with the CV-joint lash and, as @Tcoat has experienced with me hooning in wet patches, it's a recipe for some nasty flutter. I suggest simply going back to a less aggressive (stock) clutch. It's rated specifically for the strength of the transmission anyway.
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Old 11-17-2021, 02:48 AM   #12
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What make clutch?
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