DIY Hardened Transmission Mount
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This is a discussion on DIY Hardened Transmission Mount within the Powertrain forums, part of the Tutorials & DIY category; Disclaimer: I can't be responsible for you screwing up your crap I've heard of people using 3M Window Weld to ...

  1. #1
    Registered User zoinks's Avatar
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    DIY Hardened Transmission Mount

    Disclaimer: I can't be responsible for you screwing up your crap

    I've heard of people using 3M Window Weld to fill in trans and motor mounts but I prefer a 2 part liquid RTV Urethane. I used a 94A shore urethane that I purchased from McMaster-Carr for around $28. It is a premeasured 1 pound kit that is just more than enough to do the tranny mount.

    Here is a picture of the urethane...



    This first picture is the stock mount.
    The second picture shows where I removed the center rubber triangle. For this I used an exacto saw. The reason I removed this is to give more space for the urethane. I left the outer two rubber pieces and just encapsulated them. I also removed some bits of rubber that were left over from the original molding.






    Now make sure the mount is super CLEAN. Use degreaser to completely clean the mount. It's also a good idea to take some sandpaper and rough up the inside of the mount.

    Next, take duct tape and seal one side of the mount as shown below. Make sure you leave room for the bolts to go back in.



    Side that you will pour into...



    Make sure you follow the instructions on mixing. It is best to use all of it at once as it is premeasured and has to be within a 1% ratio.

    First prop the mount on something so that it is level and pour slowly.
    Here is a picture of the mount after filling with urethane.



    The urethane takes either time or heat to cure. At room temp. (77 degrees) it takes it 2 days to be 80-90% cured and 100% in 7 days. If you don't have that much time like me, you can also place it in the oven at 165-190 degrees for about 10 hours. This was per instructions from a rep. at Forsch Polymer.

    Good luck and happy hardening
    Last edited by zoinks; 04-12-2007 at 10:32 PM.

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  3. #2
    Registered User hybrid gti 2's Avatar
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    thats pretty cool!
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    what durometer are the real mounts? 94 is pretty hard but i would think those hardened STIs were harder.

    really good idea though. may look into buying a used old mount and a bucket of urethane!

    what we need now: review once installed and driven on.
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  5. #4
    Registered User zoinks's Avatar
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    Quote Originally Posted by gusto
    what durometer are the real mounts? 94 is pretty hard but i would think those hardened STIs were harder.

    really good idea though. may look into buying a used old mount and a bucket of urethane!

    what we need now: review once installed and driven on.
    I'm not sure what durometer the STi's are but 94A is pretty hard, especially in a solid chunk like that. There needs to be at least a little bit of flex so I don't think I would go much harder. I will be reinstalling tomorrow and I'll update with my impressions. Also, the stock mount can be twisted by hand with little force so any improvement will make a big difference.

  6. #5
    Registered User zoinks's Avatar
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    I just got the mount reinstalled and I can definitely tell a difference. I went for a short drive and it just feels tighter and it shifts a bit smooter now. I think it will get even better with some STi engine mounts.

    And as for the urethane, it was quite hard after it cured. Definitely can't move it with your hands anymore.

  7. #6
    Registered User yo vanilla's Avatar
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    that's pretty cool, but i don't know if its worth the $30-40 you'd save on just buying the real thing
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  8. #7
    Registered User zoinks's Avatar
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    I hear ya. However, after comparing it to an STi mount, it seems to be stiffer. There's definitely more urethane in it. Also, there is more than enough urethane in the 1 pound kit so you can make something else. I made shifter bushings but I forgot to make a tutorial. It's pretty simple though. And the price is $28 shipped for the urethane.

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    Banned C89ZX7R's Avatar
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    theres no pics here

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    Registered User wrx wagone's Avatar
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    Quote Originally Posted by C89ZX7R View Post
    theres no pics here
    This message printed on 100% recycled electrons.

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  12. #11
    Banned C89ZX7R's Avatar
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    Quote Originally Posted by wrx wagone View Post
    whats the point of this pic , i'm lost

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    Quote Originally Posted by C89ZX7R View Post
    whats the point of this pic , i'm lost
    its captain obvious
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  14. #13
    Registered User 240toSTi's Avatar
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    yeah I would like to see some pics of the tutorial.
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  15. #14
    Registered User zoinks's Avatar
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    Now with 100% more pics! Well, until I screw the links up again.

    Honestly, I'd just buy an STi mount though. If you're gonna do it, I'd probably get a urethane that's not quite so stiff. I didn't have any problems with it but it was pretty damn hard.
    Last edited by zoinks; 04-12-2007 at 10:44 PM.

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