Question about 1988 Chevrolet C1500
88 chevy silverado 1/2 ton 4x4 350 TBI with 4 speed auto. The truck makes a high pitch noise at about 35 mph but stops if you let off the gas. Ive had the rear end rebuilt since the factor posi unit spider gears were destroyed (switched it with an alburn unit from randys ring and pinion). Changed the u joints also. I know its either the transfer case or transmission but im not sure which. The 4L60E was a GM replacement at 120,000 miles ago along with the motor. As far as I know the transfer case has never been serviced and I assume that is where the problem lies.
Did you check that the noise it is not just the serpentine belt slipping on the alternator pulley.
In this case you fix it by replacing the serpentine belt or putting in tension the pulley arm.
The transmission usually does not make high pitch noises, rather scratching noise when it is faulty,
Posted on Sep 02, 2008
This sounds like maybe a U-joint froze in one direction because it only make noise under load
Posted on Sep 02, 2008
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Posted on Jan 02, 2017
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1. Start the engine when the engine coolant
temperature gauge needle points to C. Allow
the engine to idle until the gauge needle
points between the C and H (normal operating
2. Accelerate the vehicle to 55 MPH (88
km/h), then quickly release the accelerator
pedal completely and keep it released for at
least 6 seconds.
3. Quickly depress the accelerator pedal for a
moment, then drive the vehicle at a speed
of 53 to 60 MPH (86 to 96 km/h) for at least
4. Stop the vehicle.
5. Accelerate the vehicle to 35 MPH (55 km/h)
and maintain the speed for 20 seconds.
6. Repeat steps 4 through 5 at least 3 times.
7. Accelerate the vehicle to 55 MPH (88 km/h)
and maintain the speed for at least 3 minutes.
8. Stop the vehicle and turn the engine off.
9. Repeat steps 1 through 8 at least one more
If step 1 through 7 is interrupted, repeat the
preceding step. Any safe driving mode is acceptable
between steps. Do not stop the engine
until step 7 is completed. If you cannot or
do not want to perform the driving pattern, a
NISSAN dealer can conduct it for you.
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