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Old 11-01-2017, 03:08 PM   #1
SubieDuper
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Default STI vs Group N Trans Mounts

Is there a difference between STI and Group N trans mounts?
I have a 03 WRX MT and the stock trans mount is not filled in like the STI mount. The group N mount looks the same as the STI mount. If there is a difference, I assume the group N mount has a stiffer material. How can you tell them apart? Are there different part numbers / stampings? Researching on this forum I found people stating there is no way to tell the STI from the group N because it is the same mold but the materials are in fact different.
In that thread, the information did not seem to me to be definitive. Can someone confirm? Thanks.
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Old 11-01-2017, 03:15 PM   #2
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As far as I know, they’re the same as STi
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Old 11-01-2017, 03:26 PM   #3
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Same visually and functionally? Same material? Exactly the same?
So this is true: STI's use group N mounts so a STI mount is group N.
These names, group N and STI, can be used interchangeably.
Thanks for the reply.
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Old 11-01-2017, 04:52 PM   #4
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They are the same.
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Old 11-01-2017, 08:36 PM   #5
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Quote:
Originally Posted by Samurai Jack View Post
They are the same.
No, they're not.

6MT mounts:

41022FE010 Transmission Mount (STI) - Hard
ST410224S000 Transmission Mount (GpN) - Harder
ST410224S040 Transmission Mount (Competition) - Hardest

The competition model also has "STi" painted on the sides, but visually, they are impossible to tell the difference once you get them out of the box (all three are marked with the 41022FE010 part no.). I've had all three on the workbench at the same time, and the hardness of the three is definitely different.

Competition (RSD sells this as GpN, but technically this is incorrect):

The Group N mount was created during a time when the durometer of the rubber was limited by FIA GpN regulations. The competition mount was offered alongside this as a non-homologated option and was even stiffer. No GpN parts were equipped on a factory car - the USDM STI was equipped with some parts that were exclusive to the Spec C in Japan, however.

5MT mounts are where it gets fun... the last GpN homologated Subaru with a 5 speed rolled off the assembly line before 2000, so these parts are pretty ancient.

41022AC180 - Standard GC mount (5MT) Soft
41022FE020 - Standard GD mount (5MT) Soft
D1010FE020 - GpN mount (5MT) Hard
S2/MB3/505 - GpN mount (5MT) < this was a standard GC mount filled with additional rubber by Prodrive

Last edited by mrsaturn7085; 11-01-2017 at 08:51 PM.
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Old 11-01-2017, 08:47 PM   #6
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Quote:
Originally Posted by mrsaturn7085 View Post
No, they're not.
I agree with this. The GrpN mounts I bought for my 2011 STI were definitely stiffer than stock. Maybe I should look at exactly which part number I ordered.
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Old 11-01-2017, 09:26 PM   #7
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Quote:
Originally Posted by mrsaturn7085 View Post
No, they're not.

6MT mounts:

41022FE010 Transmission Mount (STI) - Hard
ST410224S000 Transmission Mount (GpN) - Harder
ST410224S040 Transmission Mount (Competition) - Hardest


41022AC180 - Standard GC mount (5MT) Soft
41022FE020 - Standard GD mount (5MT) Soft
D1010FE020 - GpN mount (5MT) Hard
S2/MB3/505 - GpN mount (5MT) < this was a standard GC mount filled with additional rubber by Prodrive
Describe exactly how much stiffer each P/N is from each other.
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Old 11-02-2017, 01:18 AM   #8
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Quote:
Originally Posted by Samurai Jack View Post
Describe exactly how much stiffer each P/N is from each other.
I had them mixed up - according to Subaru:

41022FE010 (OEM part) = Stock
ST410224S000 (STI option part) = "Rubber hardness improvement product over OEM"
ST410224S040 (GpN part) = "Further improve rubber hardness for Group N competition over product ST410224S000" - notes say 'below 80Hs' which I believe means 80A, but it may be using a different scale - this note is referencing the FIA requirement.

And what they feel like:

41022FE010 = wet chewing gum
ST410224S000 = dried-up chewing gum
ST410224S040 = could probably hammer a nail with the face of the rubber

Good enough for you?

Feel free to buy the 5MT ones to test yourself - I have no need for those mounts.

Last edited by mrsaturn7085; 11-02-2017 at 01:36 AM.
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Old 11-02-2017, 08:51 AM   #9
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Quote:
Originally Posted by mrsaturn7085 View Post
And what they feel like:

41022FE010 = wet chewing gum
ST410224S000 = dried-up chewing gum
ST410224S040 = could probably hammer a nail with the face of the rubber

Good enough for you?

Feel free to buy the 5MT ones to test yourself - I have no need for those mounts.
Are these Subaru Technical descriptions or your own?
I'd actually like to see the durometer #'s for each of these parts. It is the only true way to compare between one and the other.

When I had my 5MT, I switched out the original engine & transmission mounts to what was universally described as the "GrpN" mounts, which were also generally described as the "STi" mounts.

Again, they were generally accepted as being one and the same at that time.

I would have to look up the P/N on my spreadsheet at home to determine exactly which P/N I actually installed, but they were definitely stiffer than the OEM.

Even if I actually installed the STi mounts, as opposed to the true GrpN mounts, they are still a far cry stiffer than the OEM mounts.

Last edited by Samurai Jack; 11-02-2017 at 10:20 AM.
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Old 11-02-2017, 12:22 PM   #10
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They're my own, obviously - while I have access to a durometer tester at my job, I'd have to cut a chunk of rubber out of the mount to actually fit it under the plunger as it's a bench-top unit with only enough clearance for tiny parts and not a handheld one.

The only durometer number I can confirm is that they're all below "80Hs" which is likely around 80A.

The part that had me mixed up initially is that I had the transmission mount confused with the GD rear diff. mount. This is the part that has a standard > GpN > Competition model, with the competition mount exceeding '80Hs'.
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Old 11-02-2017, 03:14 PM   #11
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I believe the durometer ratings are " somewhere " here in the NASIOC forums. Pretty sure I saw them "way back when" but it probably would take a lot of effort to find them.
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Old 11-02-2017, 04:06 PM   #12
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Old 11-02-2017, 05:28 PM   #13
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Awesome info all.
Thanks!
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Old 11-02-2017, 06:08 PM   #14
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My opinion, FWIW........new almost anything is better than an oil soaked weathered stock mount.

In your case, a 14yo mount.

Who is going to be in the car, are you running a lot more power than stock?
If a DD and sorta stock power, even a new OEM mount is a plus, beyond that sounds like bragging rights.

You chose.

When I changed engine and trans mounts, mine were old and I did a 50% power upgrade.......so, to early stock WRX power.
If you're stock and have sensitive passengers, new stock is likely fine, group N is a small upgrade.
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Old 11-02-2017, 07:31 PM   #15
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I bought new grp N motor mounts and got a used (40k mi.) 08 STI solid rubber trans mount which should be better than my 100K mi stock wrx mount which has voids in the rubber for more flex.
Power wise I'm going for reliability #1 but couldn't pass up the crank swap for the stroker. I'll stick with the stock TD04 to start.
I also got the flat trans bushings from the 08 STI and returned the Kartboys. How much do these matter? Will the new 08 STIs be different than my 03 WRXs? The 08 STIs are way softer than the Kartboys were.
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Old 11-03-2017, 07:19 AM   #16
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Quote:
Originally Posted by fleezy View Post
Showoff!
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Old 11-03-2017, 09:47 AM   #17
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Quote:
Originally Posted by fleezy View Post
Quote:
Originally Posted by Samurai Jack View Post
Showoff!
And he didn't spell it "walla"!
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Old 11-03-2017, 12:24 PM   #18
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I found that over on IWSTI before responding, but chose to leave it out since it only actually lists one mount related to this topic.

It does seem to show that 80Hs is not the same as 80A since the bushing produced 88A in test... problem is I can't seem to find which scale uses the abbrev. 'Hs'... and there's a ton:

Rockwell
Shore
Vickers
Brinell
Knoop
Leeb Rebound

I got curious and pulled up the CURRENT FIA regulations (Appendix J, Art. 254):

"A silent block may be replaced with a new silent block, of which the shape is free and the maximum hardness is 80 shores –Type A."

So there you go - GpN bushings are 80A.

ref: https://www.fia.com/file/61688/downl...token=GTh_pd7N
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Old 11-12-2017, 02:11 AM   #19
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Originally Posted by Charlie-III View Post
And he didn't spell it "walla"!
i don't even remember what i searched =D
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Old 04-06-2018, 02:42 PM   #20
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Quote:
Originally Posted by mrsaturn7085 View Post
I had them mixed up - according to Subaru:

41022FE010 (OEM part) = Stock
ST410224S000 (STI option part) = "Rubber hardness improvement product over OEM"
ST410224S040 (GpN part) = "Further improve rubber hardness for Group N competition over product ST410224S000" - notes say 'below 80Hs' which I believe means 80A, but it may be using a different scale - this note is referencing the FIA requirement.

And what they feel like:

41022FE010 = wet chewing gum
ST410224S000 = dried-up chewing gum
ST410224S040 = could probably hammer a nail with the face of the rubber

Good enough for you?

Feel free to buy the 5MT ones to test yourself - I have no need for those mounts.
I was looking for a replacement for my STI transmission mount and I came upon this thread. Thanks to mrsaturn for figuring out the differences.

I actually bought 3 of the ST410224S040 from overseas. I figured I can bring down the shipping costs (each) by buying a few and then just selling the other 2 for a reasonable price (compared to the only US vendor) to folks who are also interested. I'll post them up for sale when I get them.
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Old 11-14-2018, 05:39 PM   #21
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Quote:
Originally Posted by kenliu84 View Post
I was looking for a replacement for my STI transmission mount and I came upon this thread. Thanks to mrsaturn for figuring out the differences.

I actually bought 3 of the ST410224S040 from overseas. I figured I can bring down the shipping costs (each) by buying a few and then just selling the other 2 for a reasonable price (compared to the only US vendor) to folks who are also interested. I'll post them up for sale when I get them.
Interested in you feedback on the ST410224S040 mount. Is is O.K. for a street car or does it transmit a lot of noise? I am trying to decide on getting ST410224S040 or the softer (but firmer than stock) ST410224S000.
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Old 11-14-2018, 08:16 PM   #22
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You will hear the gears a little but it's fine for street driving.
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Old 04-09-2019, 01:58 PM   #23
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I'm selling 2 of the ST410224S040. Please look for me in the classifieds.
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Old 09-22-2019, 04:31 AM   #24
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I’m interested in buying one from you the 040 version.
Take a look at you inbox.

Thanks,
Konstantinos
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