Century Estate Wagon V6-231 3.8L (1985)
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Final drive hum, most noticeable under light throttle acceleration.
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Gear noise (whine) most noticeable in first gear and reverse. Gear noise diminishes or becomes less noticeable after an upshift.
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Pump noise (high pitch whine) increases in intensity with increase in engine RPM. Pump noise is also noticeable in Park and Neutral operating
ranges with the vehicle stationary.
When diagnosing a transaxle for one of the above conditions, the following items should be checked first:
1. Test drive the vehicle to verify the condition. Also, verify that the noise is not transaxle final drive, gear, pump, engine or engine accessories noise. It
would be helpful to use a stethoscope or a long rubber heater hose to help pinpoint the exact source of the noise.
2. Remove the converter cover and remove the converter to flywheel (flex plate) bolts. Then pull away the converter from the flywheel without bending
the flywheel (these bolts have to be removed anyway to remove the transaxle).
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Start the engine,
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If the noise goes away, then go to step 3.
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If the noise still occurs, then take off the accessories belt(s). Start the engine again; if the noise still occurs, then it is an engine related noise
such as the engine oil pump, or other rotating internal engine components such as the balance shaft bearings, etc. If the noise stops, then the
belt(s) or one of the accessories should be repaired. Refer to the Service Manual for details.
3. Remove the transaxle and remove the channel plate. Check the following components:
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Rotate the drive link assembly a couple of complete revolutions -
does the drive link get tight on the sprockets in one or two areas? If it does, inspect all the teeth of the drive sprocket. They all must be identical
- if a couple of teeth are different or damaged, replace the suspected sprocket. If the drive link assembly rotates easily without drag or
resistance, check the following components:
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Drive link assembly for broken link(s) in any of the many rows in the assembly.
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Drive link wear - Replace the drive link if necessary.
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Drive and driven sprocket teeth. All the teeth of each sprocket must be identical - if a couple of teeth are different or damaged, replace the
suspected part(s). Also, check the areas where the sprockets ride against bearings or thrust washers for spalling or pitting - replace the
sprocket(s) if necessary.
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Drive and driven sprocket support roller bearing(s) for spalling or pitting - replace the bearing(s) if damaged or missing needle(s).
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Plastic thrust washers damaged or missing - replace, if necessary.
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4th clutch shaft bearing assembly that is missing or damaged. Remember, one needle is supposed to be missing to allow lubrication to the
4th clutch assembly.
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If all the components check out OK, then replace the drive sprocket support bearing (516, for 4T60 and THM F-7; 521 for 4T60-E).
