Driveline Mounts/Bushings FAQ - Page 2
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This is a discussion on Driveline Mounts/Bushings FAQ within the Transmission & AWD forums, part of the Tech & Modifying & General Repairs category; Installed the short shifter, and new large bushing on 2002 WRX. Cut out top mounting plate to avoid any contact ...

  1. #16
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    Kartboy Short shifter Cabin noise

    Installed the short shifter, and new large bushing on 2002 WRX. Cut out top mounting plate to avoid any contact (there was a little - but not much), lubed shifter pivots and joints with lithium axel grease and still have loud gear like noise in the cabin when under compression or acceleration. I don't have a low value torque wrench so I guessed at the tension and tried to not over tighten pivot pin. I even put metal washers on both ends of the pin bolt to try and help isolate the pin from the shifter. This radiates from the shifter lever, as touching it changes the noise.
    It is pretty loud.
    Would really perfer to eliminate the noise if possible. When the music is up not a problem, but with my wife in the car it is VERY noticable. She prefers low or no music.
    Suggestions?

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  3. #17
    Master Baiter EJ257's Avatar
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    Quote Originally Posted by SOInnkeeper
    I don't have a low value torque wrench so I guessed at the tension and tried to not over tighten pivot pin. I even put metal washers on both ends of the pin bolt to try and help isolate the pin from the shifter.
    Torque spec is 8-9 lbs. Tighten it until you feel the first bit of resistance and stop. Washers probably don't help the noise.
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  4. #18
    The Fruit mangostick's Avatar
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    I've had the group N trans mount in place for a few months now... Had an interesting epiphany today after swapping back to the factory mount and thought I'd share. To give some background the car is a 2010 standard wrx hatch w 5mt. I had previously installed whiteline rear diff mount inserts, KB subframe lockdown kit and KB sts and bushings as well as the group N trans mount.

    As mentioned earlier in the thread any stiffening of drivline mounts will decrease parasitic loss but increase nvh (only exception I've noted is the rear subframe lockdown and diff mount inserts.. In my experience, no increase in nvh with those.) There is no way around this, its the trade off you have to think about before you install stiffer mounts... but read on, there's more.

    When I swapped the grp N trans mount for the factory one some months ago I was astounded and also somewhat amused that I could literally squish the factory mount in one hand (keep in mind I'm a IT tech.. I dont have giant bear paws) but after swapping back to the factory mount today I want to share some of my findings having driven the car with both mounts.

    1 Holy crap is the car quiet inside with the factory mount.. squishy or not its soft for a reason
    2 It shifts better.. not only power delivery but its not as notchy from gear to gear.. and Its no longer finicky about going from 1st to 2nd quickly at high rpm (like just short of redline in 1st) I'll get to why this might be in a moment..
    3 Huge reduction in driveline vibration transmission into cabin going back to the factory mount (cant feel Idle in my seat bottom any more).

    Now.. the results I've noted aren't shocking when it comes to the noise and vibration reduction that factory mount provides. What IS odd though is that the shifting IMPROVED going back to the factory mount. Subaru's aren't known for silky smooth manual transmissions.. but its much better with the original mount. My theory on this hinges on two Ideas

    1 the grp n mount doesn't give or compress when loaded.. and possibly alters driveshaft angle
    2 eliminating flex at the tail of the trans but not at motor mounts and pitch stop alters the dynamics of how the assembly is designed to move around under load and during transitions from loaded/unloaded state

    Looking at number one in particular..if any of you have had experience with 4cyl rear drive IRS cars you know that driveshaft angle is hugely important.. get it off and the car shakes/vibrates like hell at any speed. Not only that but changing the angle of the driveshaft can/does put extra stress on the trans tailshaft alignment that could cause notchy shifting. Our subaru's are no different from the trans tail rearward.. we just happen to have a transaxle in front of said tail housing.

    That brings Item number two into play.. and this I think is very important now that I've gone and poked around. Without stiffening the entire front drivetrain mounting (rear diff for this part doesn't matter.. besides it should be mounted as solidly as possible.. no question about that.) The angles/direction and amount of movement have changed. This can also put side load on the tailshaft and possibly cause notchy shifting. Obviously the team of engineers at subaru that designed the driveline mounting took every factor into consideration and implemented a design that they felt made the best compromise for reliability/nvh reduction and over all function. If you study all the mounts and the directions in which they support the engine/trans assy.. its thought out pretty well and all vectors of possible movement are covered.

    This being noted, what I've come up with is that unless you stiffen ALL the engine/trans mounting you're not going to see the full benefit of that change and possibly could see negatives.

    Last but not least, if you have any concern over nvh in the car.. skip the engine/trans mounts and pitch stop. You WILL get more noise in the car.. quite a bit more. My little radio shack db meter is deceased so I couldn't test for actual numbers, but I'd go to guess its almost a 20db difference between stock and group N.

    If you want that rally car engine buzz/vibration and trans whine all the time and drive hard enough(or track the car) to need em.. by all means go for it. If you like to actually hear yourself think or listen to the radio at a human volume.. keep the factory mounts. I regularly spend hours on end in the car, so this aspect is very important to me. Call it getting old if you will lol.. but I like my hearing intact when I arrive places.

    I did also find though, that my ability to leave off the line with minimal throttle application still stands. So that, I can clearly attribute to the rear subframe lockdown and diff mount inserts. Which, I HIGHLY recommend for any/all 3G (08+ cars) .. take that slop out and it really does become a different (better) car.
    Last edited by mangostick; 03-21-2011 at 07:05 AM.
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  5. #19
    Registered User shadowpr's Avatar
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    ^ a lot of good infor there.

    I actually installed the group n engine mounts, trans mount, and a new pitch stop along with cross member tranny bushings. I notice an improved feeling in shifting, with the only exception being going from 1st to 2nd with any sort of high rpms.

    The noise is considerably louder.

  6. #20
    The Fruit mangostick's Avatar
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    See and that notchy shifting between first and second has me wondering if the driveline angle is changed when going to the group N mounts. If so.. shimming would bring it back into spec (I'm sure said spec is in the service manual) .. But that still doesn't explain why I can now rip right from first to second without notchiness or grinding with the factory mounts. Unless the wiggle is just right to "help" the trans slide into 2nd.. lol.. hell odder things have happened.
    OBP 2010 5dr *traded*
    SWP 2013 FRS
    My name is Shawn, I'm a Devout Practicalist and I'm addicted to flat4's
    This page has had 1,666 visits
    SUCH IS MANGO!

  7. #21
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  8. #22
    Registered User Brazilnut's Avatar
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    Great information, thank you for posting this!

    I'm upgrading the f/r shifter bushings on my '13 wrx and after reading this have decided to do the rear diff inserts and rear subframe inserts as well (Wish I'd thought of this when we did sway bars & endlinks. Thanks for the tip Mango!). My goals right now are smoother shifting and more power to the ground (I can tolerate some additional cabin noise but I don't want it to sound like an effin' rocket ship!). Any thoughts on doing tranny bushings while I'm at it? I'm trying to take appropriate steps so when I start staging for more power, it doesn't get wasted. Thanks in advance!

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