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Old 03-31-2011, 04:07 AM   #1
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Default Motor mounts and shifting

This probably has a very simple explanation, but I don't know squat about transmissions. I'll probably feel stupid after hearing the answer...

Question: why is it that stiffer motor mounts make shifting smoother? Is the bellhousing flexing? Doesn't seem like it can flex, but who knows.

I ask b/c I was considering the FM DP brace.
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Old 03-31-2011, 04:24 AM   #2
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The entire drivetrain is attached to the car at 4 points - two motor mounts and two diff mounts. Stiffen them up and the drivetrain rocks in the chassis less, which moves the shifter around less and makes shifting easier.
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Old 03-31-2011, 11:09 AM   #3
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could explain why i could never snap 3rd with my worn out engine mounts.
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Old 03-31-2011, 11:31 AM   #4
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"BradC" on here got his hands on this Carbing transmission brace, which I would imagine would be quite nice to have and reduce almost all drivetrain rock and reduce wear on the engine/diff. mounts as well.



They're discontinued and are as rare as hens teeth. He said something about having a similar part made but nothing ever came of that. I would love to get my hands on such a device.
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Old 03-31-2011, 12:01 PM   #5
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I'd love one of those, I'd make one, but I can't weld AL. Would probably be easy to make.
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Old 03-31-2011, 02:02 PM   #6
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Does anyone have any more information on that carbing trans brace? I could definitely look into making a run of those if people are interested.
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Old 03-31-2011, 02:06 PM   #7
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better solution to guaranteed snapping 3rd is to attach the seat to the drivetrain instead of the chassis. That way when the motor mounts wear out you can still SNAP THAT BITCH yeah baby horray!!
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Old 03-31-2011, 02:09 PM   #8
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Looked up the carbing brace, couldnt find nearly any info on it. But I did also find this trans brace idea.

http://www.miata.net/products/hot/images/rsp301-027.jpg

I'll start a thread on the idea of making these soon and see what happens.
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Old 03-31-2011, 02:10 PM   #9
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Quote:
Originally Posted by TurboTim View Post
better solution to guaranteed snapping 3rd is to attach the seat to the drivetrain instead of the chassis. That way when the motor mounts wear out you can still SNAP THAT BITCH yeah baby horray!!
I wish there was a "like" button on here, a la facebook, but instead I'll just do it this way.

LIKE!!
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Old 03-31-2011, 03:31 PM   #10
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Can anyone say "NVH"?

(LOL, disclaimer, my miata is a street car)
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Old 03-31-2011, 04:33 PM   #11
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That would be so easy to make out of steel and it still would not weigh that much.
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Old 04-01-2011, 01:48 PM   #12
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Quote:
Originally Posted by JasonC SBB View Post
Can anyone say "NVH"?

(LOL, disclaimer, my miata is a street car)
I have Mazda Comp engine mounts and ES poly diff mounts in my car - made shifting a whole lot more positive but the added NVH was surprisingly minimal. The car buzzes and shakes a bit more at idle but in all its pretty negligible.
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Old 04-01-2011, 03:26 PM   #13
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Moss used to have a similar brace but doesnt appear like it is available anymore. the picture is still up though and gives a better idea of how it mounts. Looks like it would be pretty simple for someone to make. It's basically like the Racing beat control arm brace but it also bolts to the transmission.
http://www.miatamania.com/Shop/ViewP...05&SortOrder=1
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Old 04-01-2011, 05:19 PM   #14
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I want to say that in the past a few people that ran those transmission braces ended up having ppf issues.
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Old 04-01-2011, 08:47 PM   #15
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one day I' going to install this:

It makes a difference in how much the trans moves around.
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Old 04-02-2011, 10:00 AM   #16
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Quote:
Originally Posted by Doppelgänger View Post
"BradC" on here got his hands on this Carbing transmission brace, which I would imagine would be quite nice to have and reduce almost all drivetrain rock and reduce wear on the engine/diff. mounts as well.



They're discontinued and are as rare as hens teeth. He said something about having a similar part made but nothing ever came of that. I would love to get my hands on such a device.
I have one installed and I love it. Got it for $50 locally. I want to swap the rubber bushings for something stiffer tho.
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Old 05-12-2011, 08:50 AM   #17
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Bringing this thread back-

Hussie, I have that diff. brace. It'll do more for you than your pozi hooker NSA friends. Get it.


I was skimming through pics on CR and saw this gay engine bay. But it has a rather interesting "torque brace". Looks like it has a nice rubber mount in it as well.

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Old 05-17-2011, 07:49 PM   #18
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Quote:
Originally Posted by GDSpeed View Post
I have Mazda Comp engine mounts and ES poly diff mounts in my car - made shifting a whole lot more positive but the added NVH was surprisingly minimal. The car buzzes and shakes a bit more at idle but in all its pretty negligible.
I have the same combo in my car and the car vibrates like crazy at 3500 to 3700 RPM under light load. Loud vibration in the cabin. It is kind of annoying to drive on the street it just goes nuts as you pass through that RPM range with the drive shaft ingaged.

I also took the mass damper off the drive shaft and have an unsprung 4 puck clutch with a 7 lb flywheel though with lots of overrun buzz though by taking the sprung disk out.

Based on other peoples comments I didn’t expect the diff mounts to be as bad as what I am exeriancing but maybe it is other things with my setup that are contributing.

The soft AWR engine mounts were unbearable with this combo and I went back to Mazda comps.

Bob
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Old 05-17-2011, 07:54 PM   #19
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MMR engine mounts rock my world between 1k rpm to 2k rpm on the tach. Everything vibrates, if something isn't bolted down, you gonna lose it.
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Old 05-18-2011, 12:48 AM   #20
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I had my MMR engine mounts in the car for about 10 minutes. After busting knuckles putting them in for an hour I promptly pulled them out. I did like the combo of one MMR and one stock mount. I also had MMR diff mounts in my old car and didn't mind them. I NEVER missed gears with that set up.
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