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GMC
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1990
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G 3500 1 Ton Van V8-379 6.2L DSL
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Repair and Diagnosis
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Transmission and Drivetrain
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Automatic Transmission/Transaxle
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Testing and Inspection
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Symptom Related Diagnostic Procedures
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3L80/3L80HD (400/475) Automatic Transmission
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No Part Throttle Downshifts
No Part Throttle Downshifts
1.
Vacuum modulator assembly.
2.
Modulator valve.
3.
Regulator valve train.
4.
Control valve assembly has stuck 3-2 valve or broken spring.