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Thread: Polyurethane mount filling

  1. #1
    Bearded Bastard

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    Default Polyurethane mount filling

    Before I picked up my Kota I was big in the Neon perfomance crowds. One thing I saw a lot of people do was full the factory bushings with a polyurethane mix. It gave a decent mix of flex and solid. Looking at the heavily worn trans mount on my truck I decided to swap it with a poly mount. Due to a lack of readily available aftermarket poly trans mounts I decided to fill one myself. Please note I am filling a manual trans mount but the general process will work for any mount.

    Heres some info on different hardness ratings

    durometer_scale.jpg


    I purchased a 1 pound Shore 80A polyurethane mix from McMaster Carr part number 8644K11

    http://www.mcmaster.com/#catalog/122/3689/=132ledp



    ~~~~~~~~~~~~~~~~~~~~~~NOTE!!!!!~~~~~~~~~~~~~~~~~~~ ~~~~~

    Polyurethane mixes are toxic if absorbed through the skin or ingested. Also the fumes can cause health issues if inhaled in concentrated amounts. Wear gloves and use this outside.


    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~



    I went through Amazon and purchased a new trans mount. I started by spraying the mount down with brake cleaner, scrubbing the paint off the sides of the rubber, and scuffing up the surfaces. I used a sandpaper wheel from a dremel stuck in my drill.







    To properly fill the mount you have to seal up one side. I used painters take to do seal mine. Learn from my mistake - painters tape is a very poor sealer for this as i lost 25%-30% of the mix via leakage. Next time I would use gorilla tape or a metal body tape.


    Every polyurethane setup has a specific mix of urethane and hardener. The kits are shipped in perfect blend setups designed to be combined and used all at once, however as I only needed a small amount I followed the 2 to 1 mix ratio. To properly Mix I used part of a chopstick stuck in my drill as a makeshift mixer.






    Once properly blended it was a simple matter of slowly pouring the mixes into the bushing so as to not get any air trapped inside.








    Once you have the urethane poured its time to put the mount away (preferable somewhere NOT in the house. Remember there will still be fumes) for the next week and allow it to fully cure.


    So to follow up on yesterdays work.....


    To help ensure proper adhesion of the second round of polyurethane I drilled 3 holes in the mount. One in the large opening into the polyurethane and 2 into the original rubber mount. All holes are 1/3 to 1/2 way through.



    When I pulled the tape off I was pleased to find the first pour to have completely filled in the back of the mount. I had concerns of air pockets.




    I set everything back up on my outdoor work bench as I prepared for todays pour.



    To help ensure I completely filled the bount I took and old part box, punched a hole in the top, and stuck the mount in it.



    The base comes out of the can clear



    and turns black when you pour in the liquid hardener.




    After spending a few minutes mixing the two (they dont readily mix. The base is a thick gel and the hardener pours like water.) I topped off my mount and moved it in the garage to start the curing process.







    Now on to some more important information.

    My venture into this hasnt been without some mistakes. I discovered last night after some indepth searching that I have left out a possibly very important step. Degassing. As the two components are mixed it develops air bubbles. I looked at the remains of the first pour and found something...




    THis what happens when you fail to degas. A degas chambr is any structure that you can fit your mixture in and apply a small amount of vacuum to draw out the air. Ive been considering options and next week I think Ill have the materials to make what I need. I have enough mix left I can fill the worn mount thats on the truck right now. So I will have a backup in case something fails on the one Im building. This has really got me thinking building other mount components.....




    UPDATE

    I was finally confident in the curing process enough to attempt install. Using a jack and a block of of wood I loosened up the old mount and lifted trans up enough to swap them


    As I mentioned early on the current mount had seen some better days...





    Compare this one to the first two pics of the brand new mount....



    Im once again pleasantly surprised. Someone either replaced this as some point with an oem mount of this is the factory piece. Considering the truck is 14 years old and has 179k on it I say that mount looks damn good.

    There are two 15 mm nuts that hold the mount to the cross member and one 18 mm bolt/nut combo that hold the trans to the mount. Note the cut tab on the mount installs toward the front of the vehicle




    Finally got the new mount in and bolted down.




    Post install notes


    The stick seems to shake a little less. Response to throttle increase is a bit crisper as the trans isnt moving around near as much. Stick placement in the cab has shifted slightly toward the front of the truck. This is due to the tail of the trans not sitting as low as it was. As a result I may have to once again reconsider mount options for my CB as the shifter now firmly hits it when I push the stick toward the dash. I but about 20 miles on the truck and got back under it to check the mount. I see the bushing that the trans to mount bolt runs through has slightly seperated from the polyurethane. IM not really surprised as there was no good way for me to prep that area for bonding. Ill give it another week and check it again and hopefully make one final update.
    Last edited by RC Kota; 07-11-2016 at 03:13 PM.

    US Army Vet and ASE Certified Automotive Technician

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  2. #2



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    Default

    I've thought about using a polyurethane caulk on my cab mounts to firm things up a bit...good info.
    11.27 @ 118.23
    2017 NM Mopar Challenge Series Champion

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    Bearded Bastard

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    This isnt a caulk. The caulk rates way down on the Shore scale. Depending on how this turns out I may consider branching out into items. Cab mounts would be an interesting idea. If one wanted you could even do small body height increases that way.

    US Army Vet and ASE Certified Automotive Technician

    When life gives you lemons, make orange juice and leave the world wondering how you did it!

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    niebs's Avatar
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    Good right up. I used that stuff for enclosing some thermal water heaters and crap. Smelly stuff to play with. Ive been meaning to pick some up for mounts on the truck.

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    I should have said polyurethane construction adhesive, it dries pretty hard, but this shit looks like it would work.
    11.27 @ 118.23
    2017 NM Mopar Challenge Series Champion

  6. #6
    Bearded Bastard

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    Quote Originally Posted by Adobedude View Post
    I should have said polyurethane construction adhesive, it dries pretty hard, but this shit looks like it would work.
    Are you thinking complete replacement or ?

    US Army Vet and ASE Certified Automotive Technician

    When life gives you lemons, make orange juice and leave the world wondering how you did it!

  7. #7



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    Yeah...My cage is not tied to the body.
    11.27 @ 118.23
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  8. #8
    Bearded Bastard

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    Forgive my ignorance but I'm not sure how your cage location has anything to do with body mounts

    US Army Vet and ASE Certified Automotive Technician

    When life gives you lemons, make orange juice and leave the world wondering how you did it!

  9. #9



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    The cage supports go through the cab to the frame, cab moves, cage doesn't.
    11.27 @ 118.23
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  10. #10
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    Update posted

    US Army Vet and ASE Certified Automotive Technician

    When life gives you lemons, make orange juice and leave the world wondering how you did it!

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