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The shock absorbers, also called dampers, keep the tires flat on the surface of the road while cushioning the ride against jarring bumps and dips. Without them, you would feel jolts and vibrations translated up to through the frame, resulting in an uncomfortable ride. Shocks come in two interior designs: the oil-filled tube and the gas-operated variety. Both do their jobs well but sooner or later require replacement because of wear and age. Knowing the proper length, size and design of replacement shocks will determine how well the shocks perform on the vehicle.

Instructions

1

Remove the shocks from the vehicle (the exact removal method will depend on your vehicle), and wipe them down. Examine any lettering or numbers on them. Note whether they have an aftermarket brand name printed on the tube body. A standard equipment shock has little or no writing on it and appears smaller than any aftermarket shock. To measure the shock, collapse the tube body until it seats, then measure the shock from the top shaft to the bottom of the mount with a tape measure. Write the number down. Extend the shock completely by pulling on the tube body. Measure the total length from the top shaft to the mounting bolt bracket with a tape measure. Write this number down as well.

2

Take one of the rear and front shocks to your local auto parts store, and study the parts (buyers) catalog with the help of the parts clerk. Compare the shock dimensions until you find one that matches the extended length (the more important measurement) and the collapsed length. Look for replacement shocks with the exact measurements for the extension length and the collapsed length. If you have difficulty finding the correct dimension in the catalog, purchase a replacement shock with no dimension shorter than the collapsed length.

3

Study the new shock mounting hardware to ensure the mounting bracket holes match. For older cars and trucks, ask whether the auto supply store carries an old Warshawskis or JC Whitney reference catalog.

GM and other manufacturers had a brainstorm during the late 1980s -- installing a resistor in a vehicles key to act as a second layer of security in addition to the physical lock cylinder. And it works well, when it does work -- and when you have the original key. But keys and cars dont always travel together and getting a matching key can be expensive. So youve got two options: you can bypass the whole system, or you can test the sensor to get its r-code and the right key.

Instructions

1

Remove the plastic shroud around the steering column in order to access the lock cylinder mechanism. The exact procedures for removing the plastic column covers will vary by truck, depending upon the options you specified. But look all around the shrouding, locate all the relevant screws and remove them. You should now see the ignition lock and the three wires -- orange/black, yellow and red/white -- connected to the Passlock II sensor.

2

Cut the orange/black starter wire and strip the ends so that you can reconnect it afterward. Do the same with the yellow Passlock II sensor wire. Crimp a male and female weather-tight quick-disconnect onto the ends of the wires so that you can quickly reconnect or disconnect them as needed.

3

Set your digital multimeter to read in ohms. Touch the negative (black) probe to a body ground, and the positive (red) probe to the key-side yellow Passlock wire. The resistor that your measuring is contained within the Passlock sensor itself, so thats what youll be measuring.

4

Turn your ignition key to the "start" position, and monitor the readout on your DMM. Record the reading in ohms. Repeat three to four more times, record each measurement and calculate the average. The PL2 sensor may not give the same reading every time, but the computer expects a bit of variance. You should see a reading of between 400 and 13,700 ohms; this is the resistance or "r-code" of your trucks ignition.

The gear ratio of a vehicle determines whether the vehicle will have more low end power or high end speed. A vehicle that has a lower gear in the rear differential usually gets less fuel mileage, whereas a vehicle with higher gears tend to get better fuel mileage because the engine turns less revolutions per minute. The lower the gear ratio number the higher the gear ratio. Most manufacturers gear their vehicles for maximum performance and mileage. To determine the gear ratio of a GMC or any vehicle the task is accomplished the same way.

Instructions

Raise the Vehcile

1

Park the vehicle on a level surface. Insert two wheel blocks, one on the front side of each front wheel.

2

Place a floor jack in the center of the rear differential and raise the rear wheels off the ground.

3

Set two more wheel blocks, one on the back side of each front wheel, to ensure the vehicle cannot move.

4

Spot two jack stands, one near each wheel, under the rear axle tubes.

Determining the Gear Ratio

5

Wrap a thin, flexible tape measure around the driveshaft tube near the rear yoke. Accurately measure the circumference of the shaft. Record the measurement.

6

Clamp a piece of coat hanger wire to each of the remaining two jack stands to use as a pointer. Use one jack stand as a pointer placed next to the rear tire. Make a corresponding mark on the tire sidewall that aligns exactly with the wire pointer on the jack stand. The pointer is needed to accurately record exactly one wheel rotation.

7

Clamp the end of the 16-gauge yellow electrical wire tight to the driveshaft with a hose clamp around the 6 o clock or 9 oclock position on the shaft. Bend and pull the yellow wire down perpendicular to driveshaft so the wire will be drawn up when the shaft rotates.

8

Mark the yellow wire, with a permanent marker, where it comes out from under the hose clamp -- this will be the starting point. Spot the other jack stand next to the driveshaft with the wire pointer aimed directly at the starting point mark on the wire.

9

Turn the key on, just enough to unlock the wheel and place the shifting lever in neutral so the driveshaft can be rotated.

10

Rotate the driveshaft in the direction that winds the yellow wire up perpendicularly onto the shaft like a winch cable on a winch. Keep the wire tight and the wraps tight to each other.

Stop rotating the driveshaft when the wheel turns exactly one turn. Make a mark on the last wrap of the yellow wire that aligns with the pointer on the jack stand near the driveshaft -- this will be the end mark.

11

Unscrew the hose clamp from the driveshaft. Remove the yellow wire and measure the distance accurately between starting mark and the end mark.

12

Divide the length of the yellow wire in inches by the length of the driveshaft circumference in inches; that figure is the gear ratio.

For example: The wire measured 42.375 inches. The circumference of the driveshaft measured 10.625 inches.

Divide 42.375 by 10.625-inches and it equals 3.988. Rounded off it makes a 3.99 gear ratio, which means that the driveshaft turns 3.99 times for each one turn of the wheel.

13

Remove the tools from under the vehicle and the jack stands from under the rear axle tubes. Lower the vehicle back onto the ground.

General Motors engineered the fuel system of the 1999 Chevrolet Silverado V6 4.3L with and without an evaporative emissions system monitoring system. Chevrolet designed the fuel pump as an integrated module assembly, combining the fuel pump and fuel level sensor together as a single unit. Delphi manufactures fuel pumps for General Motors. 1999 Chevrolet Silverados equipped with the evaporative emissions monitoring system also have a pressure sensor built into the fuel pump module assembly. The engine computer applies vacuum to the fuel tank and monitors the sensor to verify the tank holds the vacuum. If the tank leaks, pressure drops and the check engine light will turn on.

Instructions

1

Park the vehicle on a flat surface such as a driveway. Set the parking brake and remove the keys from the ignition.

2

Chock the front tire of the 99 Silverado with wheel chocks to prevent the vehicle from rolling.

3

Lift the left rear drivers side tire of the 99 Chevy with the floor jack. Place a jack stand under the axle tube for safety.

4

Remove the plastic lug nut covers by hand using a 3/4 inch impact socket.

5

Remove the lug nuts using the 1/2 inch drive impact wrench and a 13/16 inch socket. Remove the left rear tire.

6

Lean into the wheel well toward the front of the bed. Shine the flashlight onto the top of the fuel tank. Extend the inspection mirror to inspect the top of the fuel pump module assembly.

The fuel pump module assembly is round where it inserts into the tank, and has three fuel lines attached to it. The fuel pump module assembly also has a square four-wire harness plugged into it to provide power to the fuel pump and to measure the fuel level.

7

Look for a small black sensor with a wide flat three-wire harness plugged into it. Also inspect the four-wire fuel pump harness for a tag with three prominent letters printed on it.

Vehicles equipped with evaporative emissions monitoring have the black sensor, two wiring harnesses plugged into the fuel pump module assembly and have a code on the four-wire fuel pump harness labeled "TCF." Delphis aftermarket part number for this fuel pump module assembly is FG0053.

Vehicles without evaporative emissions system monitoring do not have the black sensor, only have one wiring harness plugged into the fuel pump module assembly and have a code labeled on the four-wire fuel pump harness labeled "TCU." Delphis aftermarket part number for this fuel pump module assembly is FG0271.