Volkswagen New Beetle. Manual - part 78

GENERAL INFORMATION 

Gear Tooth Contact Patterns 

INSPECTION 

Wipe lubricant from internal parts. Rotate gears and inspect for wear or damage. Mount dial indicator to 
housing and check backlash at several points around ring gear. Backlash must be within specification at all 
points. If no defects are found, check gear tooth pattern contact.  

GEAR TOOTH CONTACT PATTERN 

1. Paint ring gear teeth with marking compound. Wrap cloth or rope around drive pinion flange to act as 

brake. Rotate gear until clear contact pattern is obtained.  

2. Contact pattern will indicate whether correct pinion bearing mounting shim has been installed and if drive 

gear backlash has been set properly. Backlash between drive gear pinion must be maintained within 
specified limits until correct tooth pattern is obtained.  

ADJUSTMENTS 

GEAR BACKLASH & PINION SHIM CHANGES 

1. With no change in backlash, moving pinion further from ring gear moves drive pattern toward heel and 

top of tooth, and moves coast pattern toward toe and top of tooth.  

2. With no change in backlash, moving pinion closer to ring gear moves drive pattern toward toe and bottom 

of tooth, and moves coast pattern toward heel and bottom of tooth.  

3. With no change in pinion shim thickness, an increase in backlash moves ring gear further from pinion. 

Both drive and coast patterns move toward heel and top of tooth.  

4. With no change in pinion shim thickness, a decrease in backlash moves ring gear closer to pinion gear. 

Both drive and coast patterns move toward toe and bottom of tooth. 

NOTE:

Drive pattern should be well centered on ring gear teeth. Coast pattern should 
be centered, but may be slightly toward toe of ring gear teeth. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Gear Tooth Contact Patterns

  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Gear Tooth Contact Patterns

  

Fig. 1: Drive Axle Gear Tooth Patterns 

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1998 Chevrolet Pickup C1500 

GENERAL INFORMATION Gear Tooth Contact Patterns

  

GENERAL INFORMATION 

General Cooling System Service 

DESCRIPTION 

The liquid cooling system consists of a radiator, water pump, thermostat, electric or belt-driven cooling fan, 
pressure cap, heater, and various connecting hoses and cooling passages in the engine block and cylinder head.  

MAINTENANCE 

DRAINING 

Remove radiator cap and open heater control valve to maximum heat position. Open drain cocks or remove 
plugs in bottom of radiator and engine block. In-line engines usually have one plug or drain cock, while "V" 
type engines have 2, one in each bank of cylinders.  

FLUSHING 

Radiator 

Connect flushing gun to water outlet of radiator. Disconnect water inlet hose. To prevent flooding engine, use a 
hose connected to radiator inlet. Use air in short bursts to prevent damage to radiator. Continue flushing until 
water runs clear.  

Engine Block 

To flush engine, remove thermostat. Connect flushing gun to water outlet of radiator. Use air in short bursts to 
prevent damage to radiator. Continue flushing until water runs clear.  

REFILLING 

To prevent air from being trapped in engine block, engine should be running when refilling cooling system. 
After system is full, continue running engine until thermostat is open, then recheck fill level. Do not overfill 
system.  

TESTING 

THERMOSTAT 

1. Remove and inspect thermostat for corrosion and proper seating of valve. If okay, suspend thermostat and 

thermometer in a 50/50 mixture of coolant and water. See Fig. 1 . DO NOT allow thermostat or 

CAUTION: Some manufacturers use an aluminum and plastic radiator. Flushing 

solution must be compatible with aluminum. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION General Cooling System Service

  

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION General Cooling System Service

  

thermometer to touch bottom or container. Heat water until thermostat begins to open.  

2. Read temperature on thermometer. This is the initial opening temperature and should be within 

specification. Continue heating water until thermostat is fully open and note temperature. This is the fully 
open temperature. If either reading is not to specification, replace thermostat.  

Fig. 1: Testing Thermostat in Coolant/Water Solution 

PRESSURE TESTING 

A pressure tester is used to check both radiator cap and complete cooling system. Follow pressure tester 
manufacturer instructions and test components as follows:  

Radiator Cap 

Visually inspect radiator cap. If cap looks okay, connect pressure tester to cap. See Fig. 2 . Pressurize tester to 
full radiator cap specification. Replace cap if it fails to hold pressure. 

 

1998 Chevrolet Pickup C1500 

GENERAL INFORMATION General Cooling System Service