Volkswagen New Beetle. Manual - part 47

This condition can be corrected simply by cleaning the gear tooth nick or ridge with a small grinding wheel. If 
either gear is damaged or scored badly, the gear set must be replaced. If metal has broken loose, the carrier and 
housing must be cleaned to remove particles that could cause damage.  

KNOCK 

This is very similar to a chuckle, though it may be louder, and occur on acceleration of deceleration. Knock can 
be caused by a gear tooth that is damaged on the drive side of the ring and pinion gears. Ring gear bolts that are 
hitting the carrier casting can cause knock. Knock can also be due to excessive end play in the axle shafts.  

CLUNK 

Clunk is a metallic noise heard when an automatic transmission is engaged in Reverse or Drive, or when throttle 
is applied or released. It is caused by backlash somewhere in the driveline, but not necessarily in the axle. To 
determine whether driveline clunk is caused by the axle, check the total axle backlash as follows:  

1. Raise vehicle on a frame or twinpost hoist so that drive wheels are free. Clamp a bar between axle 

companion flange and a part of the frame or body so that flange cannot move.  

2. On conventional drive axles, lock the left wheel to keep it from turning. On all models, turn the right 

wheel slowly until it is felt to be in drive condition. Hold a chalk marker on side of tire about 12" from 
center of wheel. Turn wheel in the opposite direction until it is again felt to be in drive condition.  

3. Measure the length of the chalk mark, which is the total axle backlash. If backlash is one inch or less, 

clunk will not be eliminated by overhauling drive axle.  

BEARING WHINE 

Bearing whine is a high-pitched sound similar to a whistle. It is usually caused by malfunctioning pinion 
bearings. Pinion bearings operate at driveshaft speed. Roller wheel bearings may whine in a similar manner if 
they run completely dry of lubricant. Bearing noise will occur at all driving speeds. This distinguishes it from 
gear whine, which usually comes and goes as speed changes.  

BEARING RUMBLE 

Bearing rumble sounds like marbles being tumbled. It is usually caused by a malfunctioning wheel bearing. The 
lower pitch is because the wheel bearing turns at only about 1/3 of driveshaft speed.  

CHATTER ON TURNS 

This is a condition where the whole front or rear vibrates when vehicle is moving. The vibration is easily felt 
and heard. Extra differential thrust washers installed during axle repair can cause a condition of partial lock-up 
that creates the chatter.  

AXLE SHAFT NOISE 

Axle shaft noise is similar to gear noise and pinion bearing whine. Axle shaft bearing noise will normally 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Drive Axle Noise Diagnosis

  

distinguish itself from gear noise by occurring in all driving modes. Noise will persist with transmission in 
neutral while vehicle is moving at problem speed.  

If vehicle displays this noise condition, remove suspect axle shafts and replace axle bearings. Re-evaluate 
vehicle for noise before removing any internal components.  

VIBRATION 

Vibration is a high-frequency trembling, shaking or grinding condition (felt or heard) that may be constant or 
variable in level and con occur during the total operating speed range of the vehicle.  

The types of vibrations that can be felt in the vehicle can be divided into 3 main groups:  

z

Vibrations of various unbalanced rotating parts of the vehicle.  

z

Resonance vibrations of the body and frame structures caused by rotating of unbalance parts.  

z

Tip-in moans of resonance vibrations from stressed engine or exhaust system mounts or driveline flexing 
modes.  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Drive Axle Noise Diagnosis

  

DRIVE CYCLES 

OBD-II Vehicles - OBD-II Readiness Monitors 

* PLEASE READ THIS FIRST * 

ACURA 

For drive cycle test procedures, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE.  

CHRYSLER/JEEP 

1995 FCC PCM 

2.0L FWD FCC PCM Equipped Vehicles 

The following procedure has been established to assist technicians in the field with enabling and running OBD-
II Monitors on 1995 Avenger, Neon, Sebring & Talon 2.0L models equipped with FCC PCM. The order listed 
in the following procedure is intended to allow the technician to effectively complete each monitor and to set 
the CARB Readiness Status in the least time possible.  

Upstream O2S Monitor 

Perform the following:  

z

Ensure engine is at normal operating temperature, above 170°F. 

NOTE:

This article applies to OBD-II equipped vehicles only. 

NOTE:

Some manufacturers do not provide a specific drive cycle test procedure. Some 
manufacturers include drive cycle procedures as part of self-diagnostics. 
Always check appropriate Self-Diagnostics or Testing W/Codes article for 
information related to drive cycle testing procedures. Some manufacturers may 
incorporate readiness testing as a part of the DTC test. 

NOTE:

A number of vehicles have had recalls related to "Readiness Monitor" issues, or 
may have testability issues. Some vehicles may not be testable for emission 
controls. See VEHICLE RECALLS, TESTABILITY ISSUES & VEHICLES 
CURRENTLY NOT TESTABLE for details on these vehicles. 

NOTE:

Drive cycles for Acura models are also known as "System Readiness Codes". 

NOTE:

For 1995-99 models, also see TSB 25-02-98 NON TURBO GAS ENGINE I/M OBDII 
"CARB" READINESS MONITOR INFORMATION . 

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors

  

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors

  

z

Operate the vehicle for a period of time, more than 2 minutes, at a speed above 25 MPH.  

z

Bring the vehicle to a complete stop, with foot on the brake and transaxle in gear (A/T) or neutral (M/T).  

The monitor should run while vehicle is stopped with the engine idling. Wait for a few minutes to allow the 
monitor to complete before turning off engine. 

Downstream O2 Monitor 

Perform the following:  

z

Ensure engine is at normal operating temperature, above 170°F.  

z

Decel Fuel Shut-off is Active.  

z

Minimum Engine RPM = 1600 RPM.  

z

Upstream O2S is less than .471 volts.  

The PCM begins the Downstream O2S rationality test. The PCM looks at the Downstream O2S volts for 5 
seconds, if less than .295 volts, the test passes. If the Downstream O2S is greater than .295 volts, the test 
increments a count of 1 and the test is done again. A count of 3 will set a DTC and store Freeze Frame Data. 

Rich (High Voltage) Output Test 

Perform the following:  

z

Engine coolant temperature is above 170°F.  

z

At WOT TPS voltage for more than 2 seconds.  

z

Upstream O2S volts is above .490 volts.  

The PCM begins the Downstream O2S rationality test. The PCM looks at Downstream O2S volts for 5 seconds, 
if more than .608 volts, the test passes. If the Downstream O2S is less than .608 volts, the test increments a 
count of 1 and the test is done again. A count of 3 will set a DTC and store Freeze Frame Data. 

EGR Monitor 

Perform the following:  

z

EGR Solenoid is enabled.  

z

Vehicle speed more than 3 MPH.  

z

Time from Start/Run is more than 2:09 minutes.  

z

The Fuel Control is in Closed Loop.  

z

No Limp-In or OBD-II Monitor faults present.  

z

Purge is enabled.  

z

Engine coolant temperature more than 144°F.  

z

MAP Range during Monitor: 11.70" to 16.20". 

 

1998 Chevrolet Pickup C1500 

DRIVE CYCLES OBD-II Vehicles - OBD-II Readiness Monitors