Pontiac Engine >> TIMING GEAR NOISE

Pontiac Engine >> TIMING GEAR NOISE

Timing Gear Noise Or Knock On
General Motors (Pontiac) 2.5L 1-4 Engines


The following information lists characteristics of timing gear
noise to assist diagnosis of problem cases involving the subject
engines.

Loose or improperly seated camshaft timing gears are usually
loudest when warm. They are sensitive to speed only, not load
sensitive. Cam gear noise will be noticed at a warm idle and
sounds much like a loose timing chain noise. It is recommended
to remove the drive belts and use a sounding device on the timing
pointer. This will provide a definite indication of timing gear
noise.

Timing gear noise is most noticeable at about 800 rpm. It can be
heard the loudest at the timing gear cover and at the oil pan
between #3 and #4 cylinders.

If the noise has been diagnosed as timing gear related, Pontiac
Motor Division recommends AERA members use the following
procedure for checking timing gear backlash:

1. Remove the rocker arm cover and loosen all rocker arm
retaining nuts on pre-1981 vehicles and shouldered bolts on
1981 and later models.

2. Remove the timing gear cover.

3. Check the camshaft end clearance to determine if the
gear is fully seated. End clearance should be .0015 to
.005.

4. Using a magnetic dial indicator positioned on the front
face of the engine block, place it on one tooth of the
camshaft gear. Be certain that the crank gear hub is
torqued.

5. Rotate the camshaft gear back and forth. Camshaft gear
backlash should not be less than or exceed .0005 to .0095.

6. If the camshaft end clearance is over .005 or gear
backlash exceeds .010 over the above limits, the timing
gear and/or thrust plate should be replaced.


The AERA Technical Committee


September 1983 - SB 105

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