Diagnosis Of Speedometer System - GMC G Service Manual

DIAGNOSIS OF SPEEDOMETER SYSTEM

PROBLEM
Noisy Operation 1. Kinked, pinched or burned casings.
2. Bent cable tips.
3. Improper or insufficient cable lubrication.
4. Faulty driven gear or rough drive gear.
Whine 1. Oversize driven gear stem in transmission
Buzzing Sound (With 1. Shift linkage vibration.
Manual Itansmission)
Tick or Ringing 1. Faulty cable.
Sound with Jumpy
Pointer Between
0 and 30 MPH
Sticky Speedometer
1. Speedometer pointer is bent and rubs.
Pointer
Incorrect Calibration
1. Wrong transmission adapter, drive gear or
2. Oversize or undersize tires.
3. Faulty speedometer head.
POSSIBLE CAUSE
binds with adapter.
sleeve.
INSTRUMENT PANEL 8C-3
CORRECTION
1. Replace both the cable and casing. Recheck
for noise.
2. Replace both the cable and casing. Recheck
for noise.
3. Lubricate cable core with P/N 6478535 or
equivalent. Pack ferrule with grease.
4. Remove driven gear assembly from trans­
mission. Check for free rotation of gear in
sleeve. Check for burrs, flash or excessively
worn spots. If gears appear damaged or
faulty, replace and recheck for noise.
1. Replace driven gear and stem.
1. Adjust transmission shift linkage.
1. Replace cable. Recheck speedometer
operation.
1. Remove speedometer cluster or lens and
straighten pointer. Recheck speedometer
operation.
1. Check speedometer gear reference for cor­
rect application and replace if necessary.
2. Check calibration using correct tire size.
3. Remove speedometer. Repair or replace as
necessary.
L00116