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Replacing Your Transmission Mounts on your Porsche 911 Carrera
 
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Pelican Technical Article:

Replacing Your Transmission Mounts on your Porsche 911 Carrera

Time:

8 hours8 hrs

Tab:

$130

Talent:

*****

Tools:

All of them, in addition to a Sawzall, shop press

Applicable Models:

 
Porsche 996 Carrera models (1999-05)
Porsche 996 Turbo, GT2, GT3 (2001-05)
Porsche 997 Carrera models (2005-08)
Porsche 997 Turbo, GT2, GT3 (2007-08)

Parts Required:

Transmission Mount

Hot Tip:

Be safe

Performance Gain:

Car works again

Complementary Modification:

Replace clutch

As a car ages, it's very common for the engine and transmission mounts to deteriorate. The rubber that is contained within the mounts becomes old and brittle, and doesn't perform a good job of isolating the drivetrain from the rest of the chassis. Old, worn out transmission mounts can cause shifting problems because the drivetrain is no longer firmly held in its position. One sign of this failure is a knocking noise under hard acceleration and braking. A visible sign that the motor mounts need replacing is the appearance of cracks in the rubber of the mount or if the ears of the rubber mount ripped in half. The rubber will deteriorate over the years and need to be replaced, even if the car has relatively few miles on it. An easy way to check if the mount is bad is to place a floor jack under the transmission mount and jack up the transmission. If you can easily jack the transmission without also jacking up the car, it's a good sign that the mount is shot. Keep in mind that even good mounts will have a certain amount of free play in the rubber. The idea here is to determine if the transmission will jack up with little to no resistance.

The design of the transmission mount on the 996 seems to be a bit under-engineered, relying on only one central mount to secure the entire engine/transmission assembly to the car. It also seems that there is no clear way to replace the mount if the center rubber portion fails. The part doesn't even show up in the factory parts diagrams, just an obscure part number. The mount itself is pressed into the end of the transmission with no apparent way of removing it. We here at Pelican considered several ways of doing the job, using everything from floor jacks to vices to ratchet straps. Eventually, we came to the conclusion that the only way of really doing the job right is to use a press.

A press is usually nothing more than a steel frame with a bottle jack or hydraulic cylinder, used to press together or separate parts using large amounts of mechanical force. It's one of those tools that every good shop should have. It's also one of the tools that you may not find in every home garage due the space they take up and also the cost of a high quality unit. Because of this, it might make more sense to take the transmission to a shop willing to let you use one for the ten minutes it takes to press the new mount into the transmission housing.

Inexpensive shop presses are usually available at your local discount tool house for under $100. In instances like this, it sometimes makes sense to buy a cheaper one and have it around for those once in a while jobs. If you are moving on to more serious jobs, like pressing out wheel bearings on a regular basis, it's a no brainer, invest in a high quality press, or fabricate your own out of heavy gauge steel if you are a competent enough welder.

Begin by putting the new transmission mount in the freezer (I'll explain why later). Now you need to remove the transmission from the car. Please refer to our article on transmission replacement for more info. At this point, it should be readily apparent that the mount has failed. Make a note of the two nubs molded into the old mount. These nubs indicate the up and down orientation of the mount once installed. It's a good idea to make a small mark on the transmission with a sharpie or a scribe to help you line up the new mount.

If you're lucky, the rubber ears inside the mount will have torn enough to allow you to place the blade of a reciprocating saw inside and start cutting the center section of the mount out. If it has not torn all the way through, you'll need to use something like a hacksaw to cut the rubber enough to get the saw blade in. Trust me, the Sawzall is your friend. You'll be at it a long time if you intend on using a hand saw to get through the rubber. The saw makes quick work of this task. As with any power tool, always take extreme care. Make sure that the transmission is well supported and can't move. I used a ratchet strap to hold the transmission down on to the workbench. Even then, you'll need an extremely firm grip on the saw and be very careful not to saw into the aluminum outer housing. Once you have cut the ears, push the center section of the mount out.

One thing we found particularly interesting is that the outer casing of the stock transmission mount was made of plastic rather than steel as on the replacement mounts. I have yet to encounter another mount that was the same way. Our project car had only 35,000 original miles on it, so it's reasonable to assume that it is the original transmission mount. My original thought for removing the outer retaining ring left behind was to make two cuts on the ring 180 degrees from each other and then pop the two pieces out. I imagine this would work the same with steel as with the plastic. Take a hacksaw and position the blade inside the mount. Now cut the two slits 180 degrees from each other just deep enough to free the halves of the mount. Now just pop the halves out and you are ready to press the new mount in.

Now you'll have to set up the transmission in the press sideways. Typically a good press will also come with an assortment of blocks so that you can align whatever item you are pressing into whatever work piece. In our case, you'll need to support the transmission so that the mounting flange sits as level as you can get it to the face of the press. Getting exactly the right angle involves placing either metal or wood shims and blocks under various points. It will probably take a bit of time to get everything lined up just right. You will also want to make sure that you are supporting the underside of the transmission mounting "ear" on all sides. Ideally, a circular piece, 4" in diameter would be ideal. Once you have it all lined up, use a level to ensure that the mounting ear is perfectly level. It also helps to strap the bellhousing side of the transmission down to the workbench to prevent it from raising up as you press in the mount.

Now, remember how you put the new mount in the freezer? The idea behind this is to get the mount as cold as possible. As the metal freezes, it will contract and become just slightly smaller. This will help in pushing the mount into the transmission. Ideally, you'll want the mount to sit in the freezer overnight. This ensures that it will stay cold as you start to push it into the transmission. Take the new mount out of the freezer and line up the nubs in the new mount with the alignment marks you made earlier. Now set the mount in the top of the mounting ear. Ideally, you'll want to press the mount in only by the outer mounting ring. You would need to find a 4" diameter ring with a steel plate on top to clear the protruding inner portion of the mount.

However, I had quite a bit of trouble finding something that would work in this application because of the casting above the mounting ear. In the end, I decided to simply press on the center section and hope the rubber would be strong enough to hold until the metal contacted the outer edge of the mount. I used this method and sure enough, the rubber was fine afterwards.

Once everything is lined up, start pressing the mount in. Take care when you do this not to cock the mount in the hole. You risk breaking the ear off the transmission. Take your time and verify that the mount goes in perfectly straight. Keep pressing until the outer mounting ring is flush with the transmission ear. Once flush, you're all set and ready to put the tranny back in the car.

In this article, we will go over the procedure we came up with to replace the transmission mount on the 996.
Figure 1

In this article, we will go over the procedure we came up with to replace the transmission mount on the 996. It's a bit of an awkward procedure, but with the right tools, you should be able to pull it off. Begin by making a visual mark of the orientation of the mount. The flat metal portion of the mount faces up as shown here (blue arrow).

The first step is to cut out the center metal section of the old mount.
Figure 2

The first step is to cut out the center metal section of the old mount. In some cases, the center section can simply be pushed out if the rubber "ears" have ripped away from the outer ring.. In other cases, you'll need to cut these ears. If most of the rubber is already torn, you can use a hacksaw to cut away the remaining rubber to push the center out.

You'll probably want to use a reciprocating saw to cut away the ears if there's a good amount of the rubber left.
Figure 3

You'll probably want to use a reciprocating saw to cut away the ears if there's a good amount of the rubber left. If you can't get the saw inside the mount, you'll first need to cut away enough of the rubber to allow the saw blade inside. Use extreme caution when doing this, use safety goggles and make sure you have the transmission firmly supported. Also, make sure that you don't start cutting through the outer ring of the mount and into the transmission.

ThisPicture shows the center section of the mount cut out.
Figure 4

ThisPicture shows the center section of the mount cut out.

You'll now have to remove the outer ring.
Figure 5

You'll now have to remove the outer ring. We did this by making a cut along the edge of the mount, cutting just deep enough to break through the outer ring, but not cut into the transmission casting. Originally, I had planned to make another cut 180 degrees on the other side in order to release the tension on the inner ring, but as soon as I made the first cut, I realized that the ring was made of plastic rather than metal. If you have a metal ring, I would go ahead with cutting another groove 180 degrees off.

Now pry the old ring out of the transmission.
Figure 6

Now pry the old ring out of the transmission. If the ring is plastic like on our car, it will simply snap in two. If it is metal, you may need to do a bit of bending before it will come out of the transmission.

Place the transmission sideways in the press and use wood or metal to support it.
Figure 7

Place the transmission sideways in the press and use wood or metal to support it. You'll want to get the transmission ear as close to 90 degrees straight up as you can. At the same time, you'll need to support the bellhousing end of the tranny to keep it from pivoting up as you press the mount in. This is the most time consuming part of the job, making sure everything is aligned correctly. You'll also want to make sure that the edges of the ear are well supported as you could end up breaking a chunk off it. Upper left insert is the new mount.

Now grab the new mount out of the freezer and orient it in the
Figure 8

Now grab the new mount out of the freezer and orient it in the "ear" so that the flat section points up relative to the transmission. Try to get the mount as straight as possible, then use a flat piece of metal to fit above the mount. You'll notice that the center section sits higher than the edge of the mount. The rubber itself has enough flex in it to allow you to press on the center section until you hit the outer wedge of the new mount. Now work quickly and press the mount in until the edge of the new mount is flush with the edge of the ear. Voila! Your new mount is installed.

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Comments and Suggestions:
stu Comments: SSF Imported sells a tool where you do not have to remove the 996/997 transmission to replace a worn transmission mount. You can do the job in less than an hour.

Part # 10 4886 090
November 23, 2016
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it. I will have the article updated.
- Nick at Pelican Parts
 
DonB Comments: I have a 2001 C4 with the tiptronic is the procedure the same?
August 31, 2016
  Followup from the Pelican Staff: It will be similar. - Nick at Pelican Parts  
Cook Comments: What's the part number for the mount on a 2005 C2S?
December 9, 2015
  Followup from the Pelican Staff: You didn't note 996 or 997 or manual or auto. So I guessed at this part:

http://www.pelicanparts.com/cgi-bin/supertech/catalog.cgi?action=frameset&return-url=/cgi-bin/supertech/catalog.cgi%3Faction%3Dframeback%26page%3D1747&catalog-url=http%3A%2F%2Fwww.pelicanparts.com%2Fcatalog%2FSuperCat%2F0940%2FPOR_0940_TRAUTO_pg2.htm %3Futm_source%3DSuperTech%23item6


I’m not the best with part numbers.

Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
porsche996 Comments: what is the torque of the bolts that go through the mount to the trans?
December 26, 2014
  Followup from the Pelican Staff: I don't have the specs handy. I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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