The key to diagnosing the Torque Converter Clutch (TCC)
shudder is to note when the shudder happens and under what conditions:
The TCC shudder should only occur during the apply and/or release of
the converter clutch, and SELDOM after the TCC plate is fully applied.
While the TCC is Applying or Releasing
If the shudder occurs while the TCC is applying, the problem can be
within the transmission or the torque converter. Something is not allowing
the clutch to release, or the TCC is trying to release and apply the clutch
at the same time. This could be caused by leaking turbine shaft seals, a restricted
release orifice, a distorted clutch or a housing surface due to long converter
bolts, or defective friction material on the TCC plate.
Shudder Occurs after the TCC has Applied
Important: Once the TCC is applied there is no torque converter (fluid coupling)
assistance. Engine or driveline vibrations could be unnoticeable before the
TCC engagement.
When the shudder occurs after the TCC has applied, most of the time
there is nothing wrong with the transmission. As mentioned above, once the
TCC has been applied, it is very unlikely that it will slip. Engine problems
may go unnoticed under light throttle and load, but engine problems may become
noticeable after TCC apply when going up a hill or accelerating, due to the
mechanical coupling between the engine and the transmission.
Inspect the following components in order to avoid misdiagnosis of the
TCC shudder and possibly disassembling a transmission and/or replacing a torque
converter unnecessarily:
| • | Spark plugs--Inspect for cracks, high resistance or broken
insulator. |
| • | Plug wires--Look in each end. If there is a red dust (ozone)
or a black substance (carbon) present, then the wires are bad. Also look for
a white discoloration of the wire indicating arcing during hard acceleration. |
| • | Distributor cap and rotor - Look for broken or uncrimped
parts. |
| • | Coil--Look for black on bottom indication arching while engine
is misfiring. |
| • | Fuel injector--Filter may be plugged. |
| • | Vacuum leak--Engine won't get correct amount of fuel and
may run rick or lean, depending on where the leak is located. |
| • | EGR valve--Valve may let in too much unburnable exhaust has
causes engine to run lean. |
| • | MAP/MAF sensor--Like the vacuum leak, the engine won't get
the correct amount of fuel for proper engine operation. |
| • | Carbon on intake valves--Restricts proper flow or air/fuel
mixture into cylinders. |
| • | Flat cam--Valves don't open enough to let proper fuel/air
mixture into cylinders. |
| • | Oxygen sensor--May command engine too rich or too lean for
too long. |
| • | Fuel pressure--May be too low. |
| • | Engine mounts--Vibration of mounts can be multiplied by TCC
engagement. |
| • | Axle joints--Check for vibration. |
| • | TPS--TCC apply and release depends on TPS in many engines.
IF TPS is out of specification, TCC may remain applied during the initial
engine crowd. |
| • | Cylinder balance--Bad piston rings or valves that seal poorly
can cause low power in a cylinder. |
| • | Fuel contamination--Causes poor engine performance. |
