Flexplate
Every vehicle on the road has a coupler between the
engine and transmission, for an
automatic transmission
this is called the flexplate, for a
manual transmission
it is called a flywheel. This article will explain the difference between the two,
what they do and hopefully everything else you will need to know about them. A flexplate
is what connects the engine to the automatic transmission in a vehicle. It is basically
a piece of thick sheet metal that bolts to the end of the crankshaft and to the
torque converter. They are
made of a thinner material than a flywheel to allow for expansion of the torque
converter at higher engine rpms, thus the name “Flexplate”. Some flexplates have
a toothed ring on the outer edge for the
starter to engage with,
others have the toothed ring on the torque converter.Flexplates are engine specific
items due to the fact that some engines require external balancing to smooth out
vibrations, these flexplates will have a
weight welded to it somewhere, others will not. If these are mixed up, the engine
will have a serious vibration that could actually cause internal engine damage if
left unchanged. Flexplates have been know to crack and or break for no particular
reason, if your vehicle makes a
chirping
or light knocking noise just off idle in gear, you may have a cracked or broken
flexplate. If you suspect this, some transmissions have a removable inspection cover
that will allow enough access to see if there are any cracks (Look for rust, this
is a sign of a crack), but unfortunately most of the time the
transmission must be
removed to gain access to see if it is indeed cracked/broken. If your vehicles flexplate does need to be replaced, use a high quality OEM (Original
Equipment Manufacturer) part or the equivalent, a cheap one may not be made of a
high quality steel or could cause starter alignment issues. Always match up the
old one to the new one before reassembly to assure they are the same diameter and
that the torque converter and crankshaft bolt holes line up properly. The crankshaft
mounting holes are usually “Timed” which means that they will all only line up in
one spot, so you may have to rotate the flexplate a few times to get them all to
line up to verify it is the correct flexplate for your vehicle.
Flywheel
If your vehicle has a manual transmission, then it uses a flywheel instead of
a flexplate. Flywheels are much heavier than a flexplate, this is due to the lack
of a torque converter which is what helps keep the
engine from stalling or bogging
down by using its weight to maintain the inertia of the engine at low rpms. Flywheels
come in different weights depending on the application. A lighter flywheel would
be used in high-performance applications where higher rpms are the norm, a heavier
flywheel is used in trucks and other low rpm applications where you need the extra
help just off idle. Heavier flywheels also make the transition between gear shifts
smoother by maintaining the engines inertia which decreases the jerking motion felt
when letting the clutch out.
The flywheel is where the clutch assembly mounts and is the contact-friction
surface for the clutch disk. Whenever a
clutch is replaced in a manual transmission
vehicle the mating surface on the flywheel needs to be resurfaced and measured to
be sure the thickness is within specification, otherwise the flywheel can crack
and even break in extreme cases. Flywheels are where the toothed ring is mounted
for the starter motor to engage. In certain applications this ring can be replaced
instead of replacing the entire flywheel when the teeth become damaged. If you need
to replace your flywheel, always use a high quality replacement part such as the
OEM (Original Equipment Manufacturer) parts. They will fit right and perform better
than less expensive aftermarket products.
If further assistance is needed, our certified car repair technicians
are ready to
answer your car questions.
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