GMC 1976 ZEO 6083 Maintenance Manual page 468

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TRANSMISSION
CAUTION : BEFORE CHECKING TRANSMISSION FOR WHAT IS BELiEVED TO BE "TRANS . NOISE,"
MAKE CERTAIN THE NOISE IS NOT FROM THE WATER PUMP, ALTERNATOR, AIR CONDITIONER,
POWER STEERING, ETC. THESE COMPONENTS CAN BE ISOLATED BY REMOVING THE PROPER
BELT AND RUNNING THE ENGINE NOT MORE THAN TWO MINUTES AT ONE TIME .
PARK, NEUTRAL & ALL DRIVING RANGES
-PUMP CAVITATION-
OIL LEVEL LOW
PLUGGED OR RESTRICTED FILTER .*
WRONG FILTER
INTAKE PIPE "O" RING DAMAGED .
INTAKE PIPE SPLIT, POROSITY IN CASE INTAKE
PIPE BORE .
WATER IN OIL .
POROSITY OR VOIDS AT TRANS . CASE
TO PUMP COVER PLATE.
-PUMP ASSEMBLY-
GEARS DAMAGED, OR DEFECTIVE,
DRIVING GEAR ASSEMBLED BACKWARDS .
CRESCENT INTERFERENCE .
BUZZING NOISE-ORIFICE CUP PLUG IN
PRESSURE REGULATOR DAMAGED OR MISSING .
SEAL RINGS DAMAGED OR WORN .
-CONVERTER-
LOOSE BOLTS (CONVERTER TO FLYWHEEL)
CONVERTER DAMAGE .
CRACKED OR BROKEN FLEX PLATE
TRANSMISSION NOISY
FIRST, SECOND AND/OR
REVERSE
-PLANETARY GEAR SET-
GEARS OR THRUST BEARINGS DAMAGED .
FRONT INTERNAL GEAR RING DAMAGED .
Transmission Noisy
DURING ACCELERATION-
ANY GEAR
TRANSMISSION OR COOLER LINES
GROUNDED TO UNDERBODY .
MOTOR MOUNTS LOOSE OR BROKEN .
DRIVE LINK ASSEMBLY,
WORN OR DAMAGED, MAY SOUND
LIKE POPCORN POPPING .
SQUEAL AT LOW VEHICLE
SPEEDS
SPEEDOMETER DRIVEN GEAR SHAFT SEAL-
SEAL REQUIRES LUBRICATION OR REPLACEMENT .
* There is no approved way of checking or cleaning the filter . If the filter is suspected of being
plugged or restricted, it must be replaced .