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[Jason]

I have a 1995 4X4 F150. Its a 302 with 185K. Recently (3 - 4 mo) I've noticed a considerable vibration when the transmission up shifts to over-drive. I can best describe it as 5 or 6 rapid jerks usually when the engine's at half throtle or lower and I only notice it at the beginning of the drive later on it not noticeable. Fluid levels are fine. Any Ideas?

[bling]

Dealerships should have access to an EVA (Electronic Vibration Analyzer), this is a tool that utilizes a magnetic pick-up placed inside the vehicle where the vibration is felt and test driven to duplicate vibration, the EVA measures the frequency of the vibration. along with the information gathered from the EVA and gear ratio, tire size, speed at which it occurs, and a technician trained in its use can determine the location of the vibration.

The vibration needs to be broken down to a specific comonent group. It sounds as if they are only concentrating on one group, which may be the source.

After you have related a vibration to either the engine speed or to the vehicle speed, break the vibration down further in order to fit into one of the following groups of rotating components:

• The engine, the clutch disc (manual transmission), the transmission flywheel (automatic transmission), and the transmission torque converter.
• The transmission output shaft, the propeller shaft, and the rear axle differential pinion.
• The tires, the wheels, the hubs, the drums, and the rotors.

These three groups represent the major areas that can produce vibration complaints. The components in each group are related to each other because the components are either bolted or splined together. This means that each group of components rotates at the exact same speed.

These categories can be broken down further in order to identify the exact component responsible for the disturbance. The emphasis is on testing in order to pinpoint the source and to eliminate unnecessary parts replacement.

Perform a road test for ALL vibration complaints unless the disturbance occurs only with the vehicle at a standstill.

Here is some information that needs to be gathered on a road test to determine location.

Types of Road Test

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

Important: Before performing any road test, inspect the tires and wheels.

The following road test procedures are the most informative and the most used:

• Slow acceleration test
• Neutral coast-down test
• Downshift test
• Neutral run-up test
• Brake torque test
• Steering input test
• Standing start acceleration test (launch shudder)

These tests will help to pinpoint the vibration. Perform all of the tests on a smooth, level road.

Slow Acceleration Test

This test will identify those conditions which are related to the engine-speed or to the vehicle-speed. Additional tests may be necessary in order to determine the exact cause of the vibration.

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. On a smooth, level road, slowly accelerate up to highway speed.
2. Look for disturbances that match the customer's description.
3. Observe the following readings where the disturbance occurs:
• The vehicle speed, km/h (mph)
• The engine speed (RPM)
• The frequency (if possible)

Now perform the neutral coast-down test and the downshift test.

Neutral Coast-Down Test

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. On a smooth level road, accelerate to a speed slightly higher than the speed at which the vibration occurs.
2. Shift the vehicle into NEUTRAL gear and coast down through the vibration range.

Observe whether the vibration is present in NEUTRAL gear.

If the vibration still occurs in NEUTRAL gear, then the vibration is definitely sensitive to vehicle-speed. At this point, the following components have been eliminated as a cause of the vibration:

• The engine
• The transmission flywheel (automatic transmission)
• The torque converter

Depending on the symptoms or the frequency, the repair will concentrate on one of the following components:

• The tire and wheel assemblies
• The transmission output shafts
Downshift Test

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. On a smooth, level road, accelerate to the speed at which the complaint vibration occurs.

Observe the engine RPM.
2. Decelerate and safely downshift to the next lower gear.
3. Operate the vehicle at the previous engine RPM.

If the vibration returns at the same engine RPM, the following conditions are the most probable causes of the vibration:

• The engine
• The transmission flywheel (automatic transmission)
• The torque converter

Repeat this test in lower gears, and in NEUTRAL gear, in order to confirm the results.

In some cases, a vibration may also be sensitive to torque or engine load, as well as being related to a specific engine speed or vehicle speed. These vibrations can be most difficult to diagnose, and require additional testing. A systematic approach usually leads to isolating the problem.

Neutral Run-Up Test

This test is designed to identify vibrations which are related to the speed of the engine. Use this test when the customer complains of vibration at idle, or as a follow-up to the downshift test. This test probably doesn't apply when the complaint is related to vehicle speed only (appearing at the same vehicle speed regardless of the engine speed).

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. Slowly increase the engine speed while looking for disturbances that match the customer's complaint.
2. Observe the engine speed (RPM) and the frequency (if possible) where the vibration occurs.

Brake Torque Test

This test is designed to identify engine-related vibrations that were not uncovered with the neutral run-up test. This test also works for vibrations that are sensitive to the engine load or to the torque. This test will probably not apply to vibrations which are related only to the speed of the vehicle.

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. Apply the parking brake.
2. Block the front wheels.
3. Step firmly on the brake pedal.
4. Place the vehicle in DRIVE.
5. Slowly increase the engine speed while looking for vibrations that match the customer's description.
6. Observe the engine speed (RPM) and the frequency (if possible) at which the disturbance occurs.
7. If necessary, place the vehicle in REVERSE gear and repeat steps 5 and 6.

Steering Input Test

This test is intended to determine how much the wheel bearings and other suspension components contribute to the vibration, especially a vibration relating to noise, such as growl, grinding, and roaring.

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. With the vehicle at the vibration speed (mph), drive through slow sweeping turns, first in one direction and then in the other direction.
2. If the vibration gets worse or if the vibration goes away, inspect the following components as possible causes of the vibration:
• The wheel bearings
• The hubs
• The tire tread
3. The CV joint angle increases when the vehicle is turning. On front wheel drive (FWD) vehicles, CV joint condition systems may appear when the angle increases. Putting a load on the CV joint may increase the vibration amplitude. The third order, tire speed related amplitude would remain the same.

Standing Start Acceleration (Launch Shudder) Test

The purpose of this test is to duplicate a vibration called launch shudder. In some cases, a powertrain mount or an exhaust ground-out may also be the cause of the vibration, depending on the symptoms.

Caution: Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.
1. With the vehicle at a complete stop and in gear, remove your foot from the brake pedal.
2. Accelerate to 48-64 km/h (30-40 mph) while looking for vibrations that match the customer's description.

Other possible causes of launch shudder include the following conditions:

• Incorrect trim height
• A worn or damaged drive axle CV joint
• A ground-out through the engine or transmission mounts
• Faulty exhaust hangers and mounts



Hopefully this information will allow you to narrow down the vibration. If you have more questions please reply back.