Inspecting Your Tilton Cerametallic Clutch for Maintenance

When a clutch needs to be replaced due to normal wear, component failure or improper operation, it’s important to determine the cause of the failure. Many times, there are other problems that
cause the clutch to fail or wear prematurely. Without fixing those problems, your new clutch
will likely experience the same failure. Tilton’s cerametallic friction discs feature a
blend of ceramic and metallic components, which make the friction material thicker than a
metallic clutch, providing for higher heat capacity. The cerametallic clutch assembly should be checked any time symptoms of clutch wear or problems surface. The clutch assembly should be checked for any
physical damage during removal of the components. Keep on the lookout for any broken
pieces or foreign objects in the area. Before removing any parts from the clutch,
note the alignment marks of the clutch cover, floater plates and pressure plate. Keeping these marks lined up will ensure that the clutch’s factory balance is maintained, and that the floater plates are not
accidentally flipped over. Pull the entire stack out of the clutch and
place it flywheel-side down on the bench. This will make it easier to keep everything
in order for reassembly. Start your inspection with the clutch cover assembly. This consists of the clutch cover, or basket, the diaphragm spring, the retainer plate and hardware. Look for any obvious signs of damage. Pay close attention to where the legs meet the
top of the cover, as this is a highly-stressed area. Check the inside of the legs for signs of
a failed pilot bearing or bent input shaft, such as grooves cut into the clutch cover legs. Lightly tap the cover on the workbench and
listen for any loose thrust buttons, which are an indication that the clutch has been overheated and should not be reused. Next, inspect the diaphragm spring
for signs of heat damage. When the clutch is new and uninstalled, the spring will be touching the inside of the clutch cover. As the spring is used and heat-cycled, it is normal that it will lose some of its original cone angle and tension. However, the flatter the spring is when uninstalled, the less clamp load there will be when it is
drawn down onto the flywheel. If the gap between the spring and cover
looks excessive, or the spring looks flat, contact Tilton to send the clutch in
for rebuilding and spring replacement. Also, check the underside of the spring
for evidence of overstroking, such as witness marks from the
spring contacting the retainer plate. Overstroking is typically caused by not using a properly-adjusted clutch pedal stop,
and the spring should be replaced. Lastly, check the spring retaining hardware
to make sure it is not loose. Setting the cover aside, inspect the clutch stack. Start by taking the pressure plate off the stack, and using a straightedge and feeler gauge,
check for warping. Maximum allowable warping is eight thousandths
of an inch (0.008″) in any plate. Cerametallic clutch pressure plates
can be resurfaced to a minimum thickness of 449
thousandths of an inch (0.449″). Localized heat spots are harmless and can be ignored, but any small bits of friction material that may have welded themselves to the plate must be removed. Be sure to align the balance marks when reinstalling. After installing in the cover, rotate the pressure plate until it contacts the thrust buttons on one side, and use a six-thousandths (0.006″)
feeler gauge between the opposing thrust buttons and the pressure plate. This is the minimum clearance
for proper clutch release. Take the top clutch disc, and, if you did
not do so when the clutch was new, mark the order and orientation of the clutch discs
with a permanent marker. Inspect it for worn splines and cracks
in the keyhole slots of the core plate. Both of these are an indication
of gearbox misalignment. Inspect the friction material—
it should be intact and generally smooth. Measure the thickness using a micrometer. Clutch discs start new at 283 thousandths
of an inch (0.283″) thick. Discs should be replaced when the total pack
wears by 30 thousandths of an inch (0.030″). Continue with the next floater plate using
the same 0.008″ maximum for warping and 0.006″ minimum slot clearance specifications. Floaters should never be resurfaced. Here are a few key points to remember: Never install new discs with warped plates. They will not make contact evenly
across their friction faces, which will cause premature wear
and possible release issues. If the plates were warped beyond specification,
this is the time to install new discs as well. Discs will wear to match
the shape of the warped plates, and putting new plates against old discs will also cause premature wear and possible release problems. Always inspect the release bearing and
pilot bearing before reinstalling the clutch. Fresh mounting hardware is cheap insurance against a used fastener failing and damaging the clutch. For more information about
Tilton Engineering’s complete line of high-performance driveline components,

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