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Old 07-10-2009, 06:59 AM   #1
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Life of a transmission mount

Lately there have been several discussions about the front motor mount and I think we all now well aware of the symptoms and solution. Yesterday at Boardwalk Porsche their tech who works on race cars said that over time transmission mounts fail too but the degradation is less noticeable. I imagine that's because they are hydroelastic dampeners. What life span should one expect out of a 986 transmission mount and are there any symptoms indicating that it's time to replace?

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Old 07-10-2009, 08:42 AM   #2
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Originally Posted by timothy
Lately there have been several discussions about the front motor mount and I think we all now well aware of the symptoms and solution. Yesterday at Boardwalk Porsche their tech who works on race cars said that over time transmission mounts fail too but the degradation is less noticeable. I imagine that's because they are hydroelastic dampeners. What life span should one expect out of a 986 transmission mount and are there any symptoms indicating that it's time to replace?

I would think that this would be very dependent on use and abuse, ie how aggressively the car has been driven.

Hard to know what the "average mean time" to failure would be.

I bet Porsche would know.
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Old 06-29-2012, 06:03 PM   #3
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I just replaced my transmission mounts on my 2000 986 S. The symptom was drops of dark, viscous oil leaking from about 1 foot inside the rear wheel, which eventually grew worse. (This oil is the damping fluid inside the mounts). The leak was on the passenger side only, but the mechanic told me that the other mount was close to failure also.

OEM Porsche mounts were $324 each, and 4 hours labor charge.
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Old 06-30-2012, 06:47 AM   #4
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If you are replacing the tranny mounts ....

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Originally Posted by Reggie&Sue View Post
I just replaced my transmission mounts on my 2000 986 S. The symptom was drops of dark, viscous oil leaking from about 1 foot inside the rear wheel, which eventually grew worse. (This oil is the damping fluid inside the mounts). The leak was on the passenger side only, but the mechanic told me that the other mount was close to failure also.

OEM Porsche mounts were $324 each, and 4 hours labor charge.
... Don't buy the Boxster mounts.
If you purchase the Boxster mount it comes with the bracket as well with doesn't deteriorate at all.
The trick is o buy the motor mount for the 993. It is the same damper that the Boxster uses, but by itself it costs half as much.
Happy Boxstering,
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Old 06-30-2012, 04:42 PM   #5
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Originally Posted by Brucelee View Post
I would think that this would be very dependent on use and abuse, ie how aggressively the car has been driven.

Hard to know what the "average mean time" to failure would be.

I bet Porsche would know.
Bruce, I have been thinking the same thing lately. I hope in "no abuse " mode the" mount "will last for ever. (Danger, no coment ) Fingers crossed and no abuse.
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Old 07-09-2013, 11:15 AM   #6
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Looks like my trans mounts are going bad, i get a very faint rocking sensation on accel and decel and I just replaced my motor mount but the problem is still there.

My question is, does the 993 mount (993-375-049-05) also work on the S model? I have a 2003 S with a 6-speed.

Thanks everyone.
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Old 07-09-2013, 11:42 AM   #7
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Because the trans mounts are fluid filled, they will start to leak when the rubber breaks down far enough. Until they leak, its hard to know how far gone they are without removal - and once you've removed them you might as well replace 'em. Once one of them leaks, replace both.
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Old 07-09-2013, 01:00 PM   #8
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Are there upgraded, polyurethane mounts that people use? Stiffer mount and takes away the future leak issue.
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Old 07-09-2013, 03:41 PM   #9
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Don't buy the whole part for $350+. You only need the dampener which runs about 60 or so dollars and just reuse the triangle bracket. You'll need one of those star type sockets, I forget the size. Drivers side is a piece of cake, passenger side is a PITA!
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Old 07-09-2013, 10:12 PM   #10
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Are there upgraded, polyurethane mounts that people use? Stiffer mount and takes away the future leak issue.
Yes, there is a semi-solid transmission mount available. However, I wouldn't recommend this for street driving (unless you can live with it) as there will be a very noticeable increase in engine/transmission vibration.

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Old 07-10-2013, 02:35 AM   #11
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... Don't buy the Boxster mounts.
If you purchase the Boxster mount it comes with the bracket as well with doesn't deteriorate at all.
The trick is o buy the motor mount for the 993. It is the same damper that the Boxster uses, but by itself it costs half as much.
Happy Boxstering,
Pedro
@pedro - clarification only, 993 motor mount or transmission mount?
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Old 07-10-2013, 08:02 AM   #12
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@pedro - clarification only, 993 motor mount or transmission mount?
You want to use a 993 MOTOR mount. The 911's have the transmission in front of the engine whereas the Boxster has the engine in front of the transmission. Therefore, 993 motor mount serves the same purpose as a Boxster transmission mount.
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Old 07-10-2013, 08:12 AM   #13
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Quote:
Originally Posted by thstone View Post
Yes, there is a semi-solid transmission mount available. However, I wouldn't recommend this for street driving (unless you can live with it) as there will be a very noticeable increase in engine/transmission vibration.

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On Pelican Parts they suggest not to use wevo mounts on both the motor and transmission, because of the risk of knock sensors reducing power. Is this true?
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Old 07-10-2013, 09:30 AM   #14
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You want to use a 993 MOTOR mount. The 911's have the transmission in front of the engine whereas the Boxster has the engine in front of the transmission. Therefore, 993 motor mount serves the same purpose as a Boxster transmission mount.
@thstone - thanks for this. Mine is 2004 base tiptronic, does this apply or is this for manual tranny only?
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Old 07-10-2013, 09:38 AM   #15
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On Pelican Parts they suggest not to use wevo mounts on both the motor and transmission, because of the risk of knock sensors reducing power. Is this true?
Not sure about the knock sensors reducing power, but the combo of a solid engine mount with a semi-solid transmission mount will significantly increase engine/transmission vibration. You'll definitely feel it in the drivers seat. The only Boxster's that I know who run this setup are dedicated race cars.
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Old 07-10-2013, 09:39 AM   #16
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@thstone - thanks for this. Mine is 2004 base tiptronic, does this apply or is this for manual tranny only?
I have a manual - not sure about the tip. Can someone else help out?
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Old 07-10-2013, 11:35 AM   #17
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Not sure about the knock sensors reducing power, but the combo of a solid engine mount with a semi-solid transmission mount will significantly increase engine/transmission vibration. You'll definitely feel it in the drivers seat. The only Boxster's that I know who run this setup are dedicated race cars.
Been in a Cayman R with this setup and I would heed these words....you will be riding in a buzz machine....high intensity track work will block it out to some degree probably because of high rpm and concentration but for the street and low intensity track you will likely not be happy
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Old 01-01-2014, 03:32 PM   #18
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It's time to change my motor mount and tranny mount.
I am thinking of using a semi sold motor mount and just a new oem tranny mount.
Will there be a lot more vibrations because of using a semi solid mount together with a stock mount?
I am trying to get rid of the slack and stiffen up the car a little but don't want something too stiff that it is not enjoyable.
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Old 01-01-2014, 04:10 PM   #19
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Just changed out the front rubber/metal cylindrical mount in my box yesterday. Getting ready to install the engine after a complete rebuild. If you do not have access to a press, I'd suggest buying the entire aluminum mount with the insert already in it if you are going back to the stock rubber mount. I replaced just the rubber / metal cylinder using a hacksaw (removal - easy) and for installation, a large clamp, 2 1/2 PVC conduit reducer, 3 pound sledge hammer, and a machinist vice as a press. I broke the clamp, the PVC reducer, and the vice. The sledge hammer survived. My back is still sore. If I can manage to upload the photos I'll post them on the DIY section, only this is a DDIY (Don't do it yourself). If I were to do it again, I'd buy the entire mount assembly, and just bolt it in.
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Old 01-02-2014, 12:36 PM   #20
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Originally Posted by Yellow986S View Post
It's time to change my motor mount and tranny mount.
I am thinking of using a semi sold motor mount and just a new oem tranny mount.
Will there be a lot more vibrations because of using a semi solid mount together with a stock mount?
I am trying to get rid of the slack and stiffen up the car a little but don't want something too stiff that it is not enjoyable.
The semi-solid motor mount alone was too much vibration for me on the street. You could noticibly feel it (and see the vibration in the mirrors) at a stop light. That big chunk of rubber in the OEM engine mount does a surprisingly good job at dampening.

Of course, your tolerance level might be different/higher but I do drive my Boxster to/from the track and around town a bit with 450/500 lb springs and the PSS9's set to full hard so I'm not afraid of some harshness.

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