Pelican Technical Article: Replacing Transmission Mounts Wayne R. Dempsey
Time: 2 hrs
Tab: $300
Talent:
Tools:
Torx socket set
Applicable Models:
986 Boxster (1997-04) 987 Boxster (2005-08)
Parts Required:
Pair of transmission mounts
Hot Tip:
Use the 993 mounts and save some money
Performance Gain:
Reduced drivetrain vibration
Complementary Modification:
Replace front engine mount
This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your Porsche Boxster. The book contains 312 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 950+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Boxster owner's collection. The book is currently available and in stock now. See The Official Book Website for more details.
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Some of the most common parts to deteriorate on older cars are the engine and transmission mounts. After many years, 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 motor and transmission mounts can cause shifting problems because the drivetrain is no longer firmly held in its position. A visible sign that the transmission mounts need replacing is the appearance of cracks in the rubber of the mounts. The rubber will deteriorate over the years and need to be replaced, even if the car has relatively few miles on it. These mounts are also hydraulic, so if you see fluid leaking out of them, then that is also a sure fire way to know that they have failed.
The transmission mounts are fairly easy to replace. Replace them one at a time (remove and replace on one side and then remove and replace on the other side). Begin by jacking up your car and placing it on jack stands (Pelican Technical Article: Jacking Up and Lifting the Boxster on Jack Stands). Remove the pan that covers the transmission (Pelican Technical Article: Changing Automatic Transmission Fluid). Now, place a jack under the transmission to support the weight (Figure 1). Then, carefully remove the transmission mount nuts from under the car (Figure 2). You may have to use some swivel extensions to access the nuts as the exhaust components will be slightly in your way, and you will have to hold the bolts from turning at the top of the mount.
With the two bolts disconnected from the chassis, you can then remove the two bolts that hold the mount bracket to the transmission (Figure 2). These bolts thread directly into bosses on the transmission. With the bolts removed, you should simply be able to pull the mount off of the car. Installation of the new mount is as simple as bolting it back in place.
Replacement Boxster transmission mounts include the triangle-shaped bracket. At about $250 each, they're pretty expensive. While performing the installation of the Porsche 996 engine into the Boxster (see Pelican Technical Article: Boxster Engine Conversion Project), I discovered that the engine mounts from the 993 are functionally equivalent, and are sold without the triangle bracket for about one-half the cost of the Boxster mounts. You will have to carefully remove your old triangle bracket off of your old mount and install it on the new one if you decide to go this route. The stock 993 transmission mount part number is 993-375-049-05.
At the same time that you're replacing your transmission mounts, I recommend replacing the front motor mount (Pelican Technical Article: Replacing Motor Mounts). This will ensure that your entire drivetrain is stiff and firm at all times.
Figure 1
With the car raised up on jack stands, take your floor jack and support the transmission from underneath. Just push up very slightly on the bottom of the transmission so that you can support the weight of the drivetrain when you disconnect one of the transmission mounts.
With the transmission supported by your floor jack, carefully remove the nuts that attach the mounts to the chassis (green arrow). You will also have to hold the bolt head on the opposite / top side of the mount using a wrench. The yellow arrow shows the bolts that hold the triangle bracket to the transmission.
Here's a photo of the stock Boxster transmission mount. The Porsche 993 transmission mount is nearly the same, but minus the triangle bracket (inset). If you wish to use the 993 ones instead, then remove the nut that attaches the old mounts to the triangle bracket and move the bracket to the new 993 mount.
I was wondering if you have any pointers for tiptronic mounts? I managed to get the drivers side replaced, but the passengers side has been a PITA to get out. It appears I may have to remove the ATF cooler It says Modine on it, I guess thats what it is. Any pointers?
January 28, 2012
Rick
Comments: Regarding re-use of the old bracket, please elaborate on your statement "carefully remove old triangle bracket from the old mount". Any special procedure involved or just remove the torx bolt being careful not to bend/deform the bracket. I will be re-using the old brackets and replacing the mounts. I assume I will be removing the entire assembly, one at a time, from the transmission, install the new mount to the old bracket, and then install the refurbished assembly. Thanks.
August 31, 2011
Followup from the Pelican Staff: You're not supposed to put any torque on the new mounts, as they are hydraulic, and then can leak. They have a square section at the top that mates into the triangle bracket, so that when you tighten them to the bracket, they should be secure and not move. If your old mounts are really worn out, it's possible they might disintegrate when you try to remove them. I've never seen this personally on these cars, but other cars that are older can be troublesome like this. So, yes, simply remove the old torqx nut from the old mount / bracket assembly. - Wayne at Pelican Parts
BoxsterS
Comments: Hi,
I was wondering if the procedure is the same for a tiptronic? What would be a good point to put the jack under the transmission for supporting the weight?
November 29, 2010
Followup from the Pelican Staff: It should be similar, I think the transmission mounts are the same part number, although I haven't replaced them yet on my wife's Tiptronic Boxster. I would follow the procedure in the "jacking up" article, where you put the jack under the rear suspension points. It's much easier to do that. - Wayne at Pelican Parts
Check out some other sample projects from the book:
