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I have 1,200 miles on my car. Cobb STS and front/rear bushings installed. Starting yesterday (about 900 miles into the STS and bushings), a slight to moderate grinding noise began when engine braking (decelerating) in traffic. Its not the first time driving in traffic with the STS and bushings, but its definitely the first time I noticed the grinding/harshness. It is NOT typical gear whine, cause I like that sound :)

I know some NVH is normal for our cars, but it wasn't always there and it sounds pretty rough. Any cause for concern? Has anyone tried adding extra insulation to shifter area to quell some of the noises? Thanks
 

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Discussion Starter #3
I just went for a drive and it wasn't as bad as yesterday. Maybe I wasn't fully engaging the gears, like you suggested. I'll keep an ear/eye on it...
 

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Hi, I don't mean to thread jack but I just had a question about the 2012 wrx tranny power capacity and this thread had an appropriate title.

With modifications to the motor/turbo and if you don't launch hard and shift easy, what kind of power is the 2012 wrx transmission capable of before it starts to have problems, and what problems would you be most likely to run in to first?

Thanks
 

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The Fruit
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well.. that's a question that's very easy to ask and very hard to define. Basically boils down to enough is enough and too much is broken. *shrug*

seriously, not being a jerk but there are dozens of factors in play there. Even the old "glass" 5mt boxes weren't breaking on the roll.. but on launches or hard 1-2 shifts. If you baby a trans you can get it to last forever with any amount of power the car can physically make.. however that said, with power comes abuse. Everyone gets into it or shifts hard here and there. The more power you have on tap the more tempting it is to unleash it.

I've personally never launched mine but it does get its fair share of zooming through gears. 80K mi and I'm still on factory clutch/second fluid change. Shifts as smooth as any scoobie will (notchy cars by nature). Driver habbits and conditions are big factors.

Conservative guess would be around 350wTq before you're really running chance at blowing the box apart in a wrx. Even still.. this is not set in stone. I've whitnessed very factory cars have transmission issues as well as seen some pretty healthy built cars survive for years needing nothing more than regular fluid changes. The bottom line is very hard to define.

STI will be more condusive to higher power and abuse becuase the 6mt was designed to be very stout in the first place.
 

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The Fruit
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I have 1,200 miles on my car. Cobb STS and front/rear bushings installed. Starting yesterday (about 900 miles into the STS and bushings), a slight to moderate grinding noise began when engine braking (decelerating) in traffic. Its not the first time driving in traffic with the STS and bushings, but its definitely the first time I noticed the grinding/harshness. It is NOT typical gear whine, cause I like that sound :)

I know some NVH is normal for our cars, but it wasn't always there and it sounds pretty rough. Any cause for concern? Has anyone tried adding extra insulation to shifter area to quell some of the noises? Thanks
When I did the group N trans mount and shifter bushings in my 2010 I encountered a lot more noise into the car. If you pull the seats/carpet out you'll notice that all the factory sound deadener ends at about the middle of the front seats.

No bueno... makes the rest of the car like a rattle trap and it radiates all kinds of extra noise into the cabin. I snagged some dynamat door kits (cheaper than a trunk kit and same amount of material) and went to work on the passenger area floor/tunnel areas. That did take a good deal of the noise out and makes the car quite pleasant to drive for long periods of time.

The noise you're getting, does it sound like a big old truck transmission? Not grinding but sort of a loud meshing sound? If so.. that's normal (especially during compression braking and/or when load is very light on the driveline while coasting in gear) Mine has done this since I changed the shifter bushings and trans mount. That was at 3k mi or so. I'm now just under 81K mi. Do you have any issues getting into or out of gear?
 

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Discussion Starter #8
When I did the group N trans mount and shifter bushings in my 2010 I encountered a lot more noise into the car. If you pull the seats/carpet out you'll notice that all the factory sound deadener ends at about the middle of the front seats.

No bueno... makes the rest of the car like a rattle trap and it radiates all kinds of extra noise into the cabin. I snagged some dynamat door kits (cheaper than a trunk kit and same amount of material) and went to work on the passenger area floor/tunnel areas. That did take a good deal of the noise out and makes the car quite pleasant to drive for long periods of time.

The noise you're getting, does it sound like a big old truck transmission? Not grinding but sort of a loud meshing sound? If so.. that's normal (especially during compression braking and/or when load is very light on the driveline while coasting in gear) Mine has done this since I changed the shifter bushings and trans mount. That was at 3k mi or so. I'm now just under 81K mi. Do you have any issues getting into or out of gear?
Thanks for the info. I have no major issues getting into or out of gears. Sometimes 1st and Reverse are a bit stubborn, but nothing I'd consider out of the ordinary. As far as the truck transmission sound...I couldn't tell you one way or the other; BUT, it does sound like more of a meshing issue than a "something is breaking" grinding noise. I had the same sounds in my RSX-S under engine braking, but it wasn't half as loud. Maybe I'll look into throwing some Dynamat or Rammat on the floor when its audio time and not worry about the trans. Did you make a thread for the installation or follow any DIY's? :thumbup:
 

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The Fruit
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to be honest I cant remember lol.. but there might be pics somewhere around here. If I can find em I'll post them up. 10-1 your acura was just as loud, but because the trans is arranged and located differently it didn't transmit as much of the noise. I mean, my trans operates perfectly fine and sounds like something out of transformers lol. As long as you're not having issues shifting or popping out of gear or anything functionally you should be ok.

Cant hurt to take it to the dealer either just to make sure but likely its ok. Remember, the factory bushings are super soft for a reason, its so your mom n grandma like the nice quiet ride in your car (or so that subaru can sell them to mom's and grandma's) .. once you change the stiffness of those bushings you're introducing a pathway for vibration and noise through the harder surfaces. If you saw how squishy your factory transmission mount is you'd gasp. Seriously, its like jello. If you get a chance to get under the car (while its cold!) grab the exhaust just after the downpipe and pull it side to side. the whole engine/trans will move around with it! but squishy is quiet and cheaper than sound deadener. ;) Everything in your car was/is there from a cost vs result standpoint.
 

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The Fruit
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found some pics.. not the cabin ones but the hatch area. You ge the Idea though, you dont have to cover wall to wall, just enough to dampen the panels.





Another thing I did to find the really resonant panels was to tap around with index/middle finger with and see which panels were resonant (nice "poing" or "bong" noise when tapped on) those were my first targets for the mat.
 

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Discussion Starter #11
^^^Thanks for the pics. I'll definitely budget for some vibration dampening when I get around to removing the seats for audio amp installations. I'm pretty sure the dealer would just say its normal, so I'll stay tuned into the sound and see how it progresses. Thanks for the pics too :D

I'm also gonna re-inspect the shift boot area at some point to see if I can seal up some areas that would let excess noise through. Not that I want to turn the car into a Cadillac or anything...I'd just rather hear the exhaust and engine than the tranny's scratchy song.
 

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The Fruit
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I'll warn now.. it might be a scratchy you get used to lol. Under the shifter there is a good amount of factory deadening.. probably wont help much there. Its actually just to the rear of that (where the rear shifter stay bushing mounts) that doesn't have any dampening and transmits a lot of noise. Getting that area will help a good bit.
 

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If you baby a trans you can get it to last forever with any amount of power the car can physically make.. however that said, with power comes abuse.
I'm kind of surprised by that answer. According to people on the Honda boards the k series transmissions seem to break faster under a lot of torque before the high end horsepower even if the transmission is being babied. I thought the wrx tranny's might have some kind of characteristic like that.

I know you're not trying to be a jerk lol, I appreciate the input.
 

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The Fruit
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Well I mean, its simple.. more power to play with .. the more you will want to play. Its simple human nature to flex muscles once in a while. These aren't honda's either. The subaru trans are not as smooth on their best day as a honda trans is on its worst day.

side note.. not trying to be a jerk or anything, but since when to Honda's make torque? lol.. :p

The answer you're looking for is in the description of what the terms mean.

Torque is a measure of raw twisting force vs hp which is torque/time. HP increases as the rpm rises where torque comes on early and falls off as rpm rises. Once you're on the roll there is less force needed (and less generated) to keep the vehicle accelerating. High torque application happens low when the vehicle is not moving as quickly or not moving at all and more force is needed to generate acceleration. If this force and the mass of the vehicle are stronger than the parts in between... poof.. broken parts. That force has to go somewhere and it'll find the weakest point. In most factory subaru's that's the clutch but again this depends on if you're on the roll in gear or re-applying power after shifting, or during a launch. Like said, I've never seen a scoobie trans break on the roll but I've seen many transmissions (all kinds) broken on a launch or bad shift.

A very wise man once told me "make power IN gear, not between them" If gear teeth aren't fully engaged its much easier to break them. Let alone the synchros that ride between the gears that aren't designed to take full on engine power.

Wheel hop (shock loading) is another that's quite destructive. If you've ever used a trip hammer or air hammer or better yet, an impact wrench.. the affect is very similar. Instead of smooth and even delivery of power you have repeated loading and unloading of the driveline parts. That can break anything even at factory power levels. We dont have wheel hop problems but do have a decent amount of lash (play) in the driveline that contributes to the rapid load/unload situation. Personally I'd rather receive a progressive powerful shove vs a rapidly repetitive punch in the chest.. transmissions aren't any different.
 

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side note.. not trying to be a jerk or anything, but since when to Honda's make torque? lol.. :p
A K24 can spool a turbo quick enough to break a K series tranny pretty quick, even from a roll. You said that you've never seen a scoobie trans break on a roll and that the clutch is usually the weakest point. I guess that's what I was curious about.

I don't think I needed the hp/tq lesson but thanks... I guess...?

At least you answered my question, haha. Thanks.
 
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