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Hello? Anyone out there? Need help with decel noise.....

1871 Views 13 Replies 8 Participants Last post by  Midwayman
Ok GC8 people. I'm tired of trying to fix this freaking noise.

I'll tell you what it is: STi tranny and motor mounts.

If you have STi tranny and motor mounts on your car, please post in this thread with your comments regarding the freaking awful loud decel noise coming out of the tranny.

Since I have installed the STi mounts, STi short shifter, and Kart Boy wshifter bushing, I have this gut wrenching grinding noise that you can hear as you decelerate in any gear. I know that the noise is from the rock hard bushings and such, but damn, there must be a way to make this thing quiet.

Maybe I can wrap the tranny in "DynoMat" or something. Everytime someone rides in my car they say, "Hey dude, what's up with your tranny?"

Anyone have any ideas? I tried to insulate the front and rear tranny crossmembers with rubber washers, and it did make it less noticable, but it was still there.

I'm actually thinking of putting that weak tranny mount back in, just to shut it up. If you are accelerating, it's perfectly quiet, but take your foot off the gas and the hounds of hell start to come through the floor.


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The tranny mounts don't change anything with the geometry of the driveline do they?

The STi tranny and motor mounts are as hard as concrete and they transmit all of the tranny noise through the floor of the car.

I would like to isolate the tranny mount somehow so the vibrations don't make it as far as the cross members.

I'm still thinking about it......:rolleyes:
My Jeep made noises too. It's the differential in my opinion.

Solution - put an open center diff in. :)

My Jeep had one of those gerotor pumps on the center diff and it made all kinds of gnarly decel noises.

Maybe putting a locker would fix it too.
Hey Al,
I have the noise as well, but it isn't as loud as you describe. Nobody else in the car can hear it unless I point it out. I also have the Sti tranny mounts, but I haven't put my engine mounts in yet. I don't think it is due to the mounts as I didn't begin to hear it until a couple of months ago, but I put the tranny mounts in about a year ago. I am considering getting it checked out. If I do, I will let you know the diagnosis.

I’ve also got the STi tranny and motor mounts, but not the short shifter or bushings.
There’s somewhat noticeable vibration, particularly when I accelerate – but no deceleration noise.
I think I have found a solution....

Well, I think I may have found a solution. There is a sound deadener called "brown bread" that is similar to dynamat, but costs less.

I am pulling my seats and carpet out today and I am filling ion the areas on the floor that do not have the factory Subaru deadener.

I am wrapping it around the entire shifter mechanism and on all three crossmembers below the transmission.

I'll let you know how it goes....

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I had the exact same noise from my car. It turned out to be the rear heat shield that goes over the center section of the exhaust. I know you don't think that is the source of the sound, I didn't either. Just remove that shield and see if it makes a difference...
I'll try it.......

Hell, I'll try anything. I'll pull that bastard off tomorrow and drive it.

Stay tuned......

my whole car, sans the doors, is "dynomated" and I removed the engine mounts, and it still makes a decel noise. But im over it, that trans mount is too good to remove.
Ok now its getting annoying, I even removed the STi engine mounts, and the damn tranny still makes ALOT of decel noise, more than it did before, even with the harder mounts.
im wondering if its BECAUSE there is a hard tranny mount and not hard engine mounts, that somehow the mixture of the two doesnt work?
The STi tranny mount is hard as a rock....

The STi tranny mount is hard as a rock. In fact, I think it's too damn hard. I am going to drill 1/2 inch holes through the rubber to give it some "flex".

I'll let you know how it works out.

I thought the decel noise was a clutch issue. This is not a fix but or a workaround, but if you reduce tire pressure in the front and a bit more pressure in the back (i'm not talking drastic changes) you should be able to decrease the noise. Like i said its a symptom not a fix. If you do this and you do not hear the decel noise, i blelieve it may be the clutch.
good luck to you.
I have both the STi engine and tranny mounts and have no decel noise... well at least not exhaust related. But if its out of gear its quiet.
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