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One of the most common parts to deteriorate on the BMW is the engine and
transmission mounts. The rubber that is contained within the mounts becomes
old and brittle, and doesnt 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. One sign of this failure mode is the gearshift
knob jerking backwards under hard acceleration or difficulty selecting gears
during cornering. A visible sign that the motor 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.
The transmission mounts are easier to replace than the engine mounts, and
are very similar on both the E30 and E36 BMWs. A transmission mount
bar is bolted to the rear of the car and supports the transmission.
Begin by jacking up your car and placing it on jack stands. Now, place
a jack under the transmission to support the weight. Then, carefully
remove the transmission mount bar from the car (Figure
Figure 2). You may have to bend the heat shield slightly out of
the way to access the bolts that mount the transmission bar to the chassis.
Close-up views of the old transmission mounts are shown in
old mount by removing the nut on the underside of the mount bar (Figure
6). New mounts are shown in
and are simply bolted in place of the old ones. There is a boss on the
bottom of the mount that needs to line up with a notch on the transmission
mount bar. This boss/notch combination prevents the transmission mount
transmission mounts are not known for their performance or reliability.
The purpose of the transmission mount is to isolate the chassis of the car
from vibration that the transmission will transmit during normal driving.
The transmission is connected to the engine, and has a tendency to twist and
turn as the car accelerates or decelerates under heavy braking. If the
transmission mounts are flexible and sloppy, then there may be a
misalignment of the transmission with respect to the chassis of the car.
This may cause what is commonly known as a miss-shift or in laymen's terms a
"moneyshift." A mis-shift will sometimes cause the driver to
accidentally shift from a high gear to a much lower gear and over-rev the
engine. An over-rev is very damaging to the engine and typically
results in the valves hitting the tops of the pistons and bending.
is to use the early style BMW 320i transmission mounts. They are
thicker, they have a tendency to flex less than the stock ones, and for the
most part they are a bolt-in application. Another solution is to use
better designed transmission mounts and brackets. I recommend the ones
produced by UUC Motorwerks. The standard mount is shown beside the UUC
Figure 8. These new and improved mounts isolate vibration, but
perform a better job at keeping the transmission correctly aligned with the
chassis. In addition to the UUC transmission mounts, I also recommend
the UUC Tranny Mount Enforcers (TMEs, shown in
The TMEs hug and constrain the transmission mount and reduce the deflection
of the amount under vigorous driving. The addition of the UUC mounts
and the TMEs are probably the best insurance you can provide to prevent
upgraded UUC transmission mounts are available in black or red. The
black versions are tailored to street driving - the red ones are designed
for track or autocross use.
shows the red UUC transmission mounts installed on the transmission mount
bar. Grease up the inside of the TME prior to installation, to
minimize chaffing of the mount (Figure
12). The TMEs are installed on the top of the transmission mounts,
beneath the transmission mounting flange (Figure
Figure 14). The flange from the transmission mount should fully
protrude through the TME as is shown in
completed mount assembly is shown attached to the transmission in
The transmission shown in these photos was out of the car for a clutch job.
When installing the mounts back into the car, tighten up the bracket to
chassis bolts first. Then lower the transmission onto the bushings and
tighten the top nuts, securing the transmission to the bar.
are finished, you should feel an improvement in the shifting of your car,
and the drivetrain vibration should feel a little tighter and less sloppy.
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