Custom Auto tranny mount

Post by **Legacy777** » Fri Oct 17, 2003 2:43 am

I'm sure some of you know there is no sti mount for the autos. there's been some discussion about filling the mounts with urathane.

Well I finally got around to it tonight.

Here's one of the initiating threads over on nasioc
http://forums.nasioc.com/forums/showthr ... id=4792021

Here's a quick write up I did over there on the process

I got my 3M goo today.

I have heard some people said doing this is a mess and can be a pain.

I'll pass on some hints and procedures......I wore gloves but really didn't get messy at all.

First of all I cleaned the tranny mount out with a file to get rid of the paint and get to rubber. cleaned surface with brake cleaner.

I then fabbed up a backing plate type thing out of cardboard that fit on the one side of the mount. I then took a piece of wax paper traced around the cardboard plate. When I cut it out, I left about 1/4" around the traced marking. I then put the wax paper down on the mount and put the cardboard piece over it, and taped the cardboard piece down.

I then flipped the tranny mount over, and started filling it with the 3M goo.

I was going to use my caulking gun, but the tube wasn't cooperating, and I didn't want to get black goo all over my nicer caulking gun, So I just squeezed the tube by hand. The goo fills in the cracks on its own. It's really nice like that. I did fill in the outer portions as well. There was a little seepage on the outer areas, but it shouldnt' be too bad.

I may add a little bit more on the outer areas when everything dries to the point where I can take the cardboard backing off.

Hopefully the wax paper won't stick too bad. It may....it may not. Another thought would be to use aluminum foil.

Anyway, I will probably wait a few days before I put it on. I know the window guys say to leave that tape on for a week or so. So I probably won't put the mount on until next weekend.

Here's some pics

http://www.main.experiencetherave.com:8 ... annymount/

vrg3 · Post by **vrg3** » Fri Oct 17, 2003 2:49 am

Pretty cool... What shore hardness did you use?

I was thinking of doing this but just using plastic wrap or something to seal the bottom. It doesn't matter if it sticks, right? You can just cut away the part that didn't stick.

Post by **Legacy777** » Fri Oct 17, 2003 2:56 am

shore hardness?

Not really sure. The stuff I used is called 3M window weld. It's the same black urathane that window installers use to put new windows in.

There may be different stuff out there, but others have used it on nasioc and on the internet.

Yeah if it sticks.....no biggy.....I'll either scrape it off, or just leave it there......it'll either eventually burn off or just get dirted over.

vrg3 · Post by **vrg3** » Fri Oct 17, 2003 3:06 am

Polyurethane's rigidity is usually specified as its "shore hardness." I remember trying to decide whether to use 80A or 90A shore hardness. I don't have any point of reference though.

I think Window Weld is the stuff Sport Compact Car used on their Sentra.

Let us all know how the stuff feels! I still haven't put in my new motor and transmission mounts so I could still fill them in.

Did you start with your old mount or a new one?

dagsy · Post by **dagsy** » Fri Oct 17, 2003 6:05 am

what do you hope this will do? is it like replacing suspension bushes with poly stuff?

Post by **Legacy777** » Fri Oct 17, 2003 2:17 pm

Yeah I remember hearing that SCC used the stuff.

I bet we could dig up some technical specs on the stuff from 3M's site. There wasn't any relavant info on the tube.

Yeah, I'll let ya know how it firms up. I checked it this morning and it was still rather soft.

I decided to go with a new mount, mainly because of the miles on the current one.....plus I could fiddle with it in my spare time and not have to worry about my car being down.

For those with a MT equipped car, I'd probably just recommend getting the STi one.

dagsy, yeah this would be comparable to upgrading the suspension bushings to polyurethane. The AT tranny mounts are definitely rather flimsy.

vrg3 · Post by **vrg3** » Fri Oct 17, 2003 3:07 pm

Cool, I've heard that doing it on old mounts doesn't really give you the full experience, since the old rubber still flexes a lot.

Post by **Legacy777** » Sat Oct 18, 2003 5:54 am

Well.....so far, I'm not real impressed. The urethane is not drying or hardening up. I don't know if it needs heat......or what. I'm going to try sitting it out in the sun tomorrow.

I could put it in the oven, but I don't really want to do that.

If it doesn't harden up in a week......I'll have to think of something else. I'll probably scoop out the stuff I have in the mount now.

vrg3 · Post by **vrg3** » Sat Oct 18, 2003 6:34 am

From what I understand, the stuff is meant to be applied pretty thinly in normal use, so it takes a really long time (like a week) to set when used this way. Heat can help, but too much can make it bubble and stuff.

dagsy · Post by **dagsy** » Sat Oct 18, 2003 10:18 pm

if the goo is the same stuff as what they use for putting windsreens in, it doesn't set hard as it needs flex so the screen doesn't crack when the car flexes. or so i've been told

LaureltheQueen · Post by **LaureltheQueen** » Sun Oct 19, 2003 9:23 am

I'd just let it dry in a warm, dry place, but not hot. The heat may just soften up the poly even more.

JasonGrahn · Post by **JasonGrahn** » Mon Oct 20, 2003 6:44 pm

I think that's because you've used Urathane instead of POLY-urathane.

The window-weld goo that i've used before stayed a bit flexible throughout the couple of months that i had it installed on my car. When i picked up a spare and filled it with polyurathane, the end result was a much stiffer mount!

Urathane is made to flex/expand/contract with weather i believe, thus the reason they put it on windows. Polyurathane is very rigid, used for making skateboard wheels.

Post by **Legacy777** » Mon Oct 20, 2003 7:21 pm

I don't know if I want a polyurethane stiff bushing.....but I definitely need something stiffer then what I have. vrg3 mentioned about the shore hardness.....maybe I can try to find one with a stiffer shore hardness.

vrg3 · Post by **vrg3** » Mon Oct 20, 2003 11:07 pm

I've heard the terms urethane and polyurethane used interchangeably. A "urethane group" is a particular submolecular group, and polyurethane is a polymer of urethane groups.

I think the big deal is the shore hardness... Like dagsy said, if it is the same stuff they use to glue in windshields it would make sense that it would be fairly flexible. 3M probably makes a whole line of products with the Window Weld name on them.

McMaster sells urethane casting compounds of varying shore hardness. I think it's $23+shipping for a pound of 80A.

Post by **Legacy777** » Tue Oct 21, 2003 3:52 am

Update on the urethane on the tranny mount. It's not hardening up, and is not working. Someone recommended a two part epoxy from mcmastercarr

http://www.mcmaster.com/

Enter this part # 8644K11

Has a shore hardness of 80A

looks like same stuff you recommended vrg3.

vrg3 · Post by **vrg3** » Tue Oct 21, 2003 4:11 am

Yup, that's the stuff. They also have some other hardnesses listed if you click on the link to the catalog page, as well as some putties and stuff.

mikec · Post by **mikec** » Thu Oct 23, 2003 3:14 am

My brother and I are looking at doing this with our mushy mounts. Would polyurethane be too firm? I'm trying to figure out how much of a difference there is between polyurethane and urethane, but I guess the real answer comes from feeling them.

Any updates Josh?

Post by **Legacy777** » Thu Oct 23, 2003 3:30 am

well the 3m window urethane was a bust....shit didn't work, and did my best to clean out most of it from the mount. I'll probably get that stuff from mcmastercarr and try again.

vrg3 · Post by **vrg3** » Thu Oct 23, 2003 4:16 am

Like I said above, I don't think there's a semantic difference between "urethane" and "polyurethane." It just depends on who's selling it to you.

I did some Googling and apparently the McMaster stuff is quite popular for this application.

mikec · Post by **mikec** » Thu Oct 23, 2003 5:00 am

Cooool.

Now to see how much shipping is to Canada.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Custom Auto tranny mount

Custom Auto tranny mount