Gearshift Isolation Mount Upgrade/Repair

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Steph
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Gearshift Isolation Mount Upgrade/Repair

Postby Steph » December 1st, 2011, 7:24 am

I decided to repair and upgrade my gearshift isolation mount before I do my hondamatic to manual conversion. There were two 79 manual 1200s at the wreckers where I obtained my parts for the conversion from, and both isolation mounts had rips in the thin membrane part. The membrane is only there as a weatherseal, as it's too thin to do anything else, and on either side of the mount are two thick rubber sections which are where the strength of the mount comes from. If you look at the first picture you'll get an idea of what I mean...

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And here's a shot of the bottom..

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To strengthen the mount I used Sikaflex 227 which is a high grade self curing polyurethane which is made in Japan, so you know it's top quality! :wink:

Sikaflex 227 is an automotive grade PU that can be painted over. In fact it's the stuff they use to smear between joins in the body, where it seals up gaps, and can then be painted over. One example is behind the strut tower where Honda used tons of the stuff when they built the Civics. I found out about the product by reading around the local forums, where guys were routinely using it to make engine mounts. They would burn or drill/cut the rubber out of old mounts, and then refill the mount with Sikaflex 227. They would then wait a week for it to cure, and then refit them with great results. One of the great things about it is it's available at Bunnings here in Australia for under $15 and that gets a 310 gram tube (caulking gun size). I accidentally bought white urethane, whereas I intended to buy black, but it turns out it made it easier to see in the photos, and you won't see it once it's fitted anyway. I used about a 1/4 of the tube to do my gearbox isolation mount.

http://www.sika.com.au/cmi/pdfs/TDS_Sikaflex227.pdf

The first thing I did was thoroughly clean the rubber with paint thinners on cotton ear buds. The thinners removes the mould release residue left behind from when the mounts were first made. It takes a lot of patience but eventually the rubber will look like new again. Once the inside was all clean I proceeded to remove the membrane with the Olfa knife. I didn't want the membrane in there because I wanted to fill the top and bottom of the mount, and I wanted the two sections to bond together and create one solid piece. This will ensure the urethane stays in place even if it works itself free from the metal shell. Below you can see where I planned to cut, with the little arrows showing each end of the section I wanted to remove...

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Here it is with the membrane removed...

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Next I needed a 'plate' to block off the bottom so the Sikaflex didn't fall out when I tipped the mount right side up. I used a plastic lid off a Cadbury hot chocolate tin that I coincidentally had lying around. :P

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Cutting around the centre piece I ended up with the perfect size...

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Then I filled the bottom section of the mount being careful not to create any air pockets...

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Then I put the Cadbury lid in place and wiped off what squelched out the sides.

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I then put lots of masking tape over the plastic cap to both hold it in place, and stop the air from getting to it... more about that later..

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Now I flipped the mount over to its upright position, as it would be seen when mounted in the car...

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From here I preceeded to fill the top with urethane, and then I used the thin metal spatula to run around and remove any excess, and leave a nice smooth surface. It was a bit like smoothing the icing on a cake! :)

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From here I'll leave the top part exposed so it cures overnight. Tomorrow I'll remove the Cadbury lid from the bottom where the urethane will still be uncured, so then I can level it off like I did on the top with the spatula and have a nice tidy job. I'll post some more photos once it's finished. I expect it will take at least a week before it's fully cured, so this isn't something you can do one day, and be driving the car the next.

to be continued...
Last edited by Steph on December 1st, 2011, 3:38 pm, edited 1 time in total.

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Layspeed
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Postby Layspeed » December 1st, 2011, 12:16 pm

nice job Steph, I did the same thing to my wagon and Annie's but didn't do it as thoroughly as what you've done. I haven't seen one of those bushings that didn't have tears in the rubber.

steve.ewing@ottawa.ca
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Postby steve.ewing@ottawa.ca » December 1st, 2011, 12:53 pm

Great write up Steph. Really interested in the product you used. I used a sikaflex product 20 years ago when I used to restore wooden boats. It was expensive then but top quality. 227 looks like good stuff. I'll keep it in mind if I come across anything that I can't fix with a hockey puck.

Steph
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Postby Steph » December 1st, 2011, 7:27 pm

steve.ewing@ottawa.ca wrote:I'll keep it in mind if I come across anything that I can't fix with a hockey puck.

I forgot about the Canadian proclivity for fixing things with hockey pucks and duct tape. Don't forget what Uncle Red says, "if women don't find ya attractive, they should at least find ya handy". :P

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Postby bob78cvcc » December 3rd, 2011, 6:30 pm

Nice write up Steph. I have bookmarked it. :)

Steph
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Postby Steph » December 3rd, 2011, 11:25 pm

Thanks Guys!

Well the mount has been curing up really nicely. It still has some movement, buy waaay less than it had. It's still flexible enough not to have any chance of introducing vibration, but at the same time it's rigid enough to improve shifting. I couldn't be happier with the finished result, but fixing the mount is just one spot where movement can be minimised.

The ball near the bottom of the gear stick pivots in a special plastic moulding. Now the plastic used is nothing short of amazing, as after all these years it's still in excellent shape, even though it's probably seen a million gear shifts! There wasn't a lot of play in this joint, but I really wanted to do a first class job and take full advantage of the upgrading of the mount, so I came up with an idea to use some brass shim material I had in the garage. I bought it from a hobby shop that sold remote control vehicles and model paints and such. I can't remember what I bought it for originally, but I've found it's come in hand for a few things. I used a piece the other day when I put the indicator/wiper switch assembly back on the steering column. There was some play between the assembly and the steering column, and there was no way to adjust it out, so I just wedged a little piece of the 0.5mm brass shim between the steering column and the control assembly and with a little effort it pushed back into place and the play was eliminated.

So anyway, here's the base of the shifter mechanism with the brass shim and shifter bush...

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The plan is to wedge the shim in between the shifter bush and the shifter base... err derrr :P

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So I installed the shim with the shifter in place, and the play was completely eliminated. It wasn't so tight that the bush was binding on the ball, but it was tight enough that there was zero play in the joint. You could use anything really, even some tin from an old tea container, I just used the shim because it was handy.

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Postby Bill » December 4th, 2011, 3:42 am

Cool setup, did you use any lube on the shifter ball on reassembly?

Steph
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Postby Steph » December 4th, 2011, 4:02 am

I'll be using moly grease from Penrite, Bill.

Any recommendations?

http://www.penriteoil.com.au/products/g ... p_3percent


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