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I have a '92 chevy silverado (240,000 miles) 5.7 cdi, 4 speed auto transmission, with 3.42 positive traction rear end. I have developed a howling noise in the rear end. I replaced all U-Joints, mid drive shaft bearing noise continues. Differential has never ran low of oil and I've always used special additive for locking differential in the gear oil. My testing leads me to the roaring being in the differential "chunk." Rear wheel bearings sound normal even jacked up and tires removed. Gear oil level great. Bearing at differential front that attaches to drive shaft has no end/side shake. Could noise be in the lockup (positive traction) portion of the differential ?
Anyone ever experienced this problem
 

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I will need some more information. Is the vehicle 2wd or 4wd? Is the noise more toward the rear of the vehicle or the middle? What kind of "special additive" did you use? Try to rotate the drive shaft with the vehicle in neutral (wheels chucked) on the ground. If there is no play that is not good and so is a lot of play. There should be a little bit of play.
 

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2021 GMC Sierra Denali CC 4WD Ultimate 6.2L
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Your truck does not have posi-traction from GM. Posi is a old name for Chevy's muscle car limited slip differential. Trucks use a locking differential and the use of limited slip additives can cause problems in the locker. GM locker does not require any additive.

The locker will not function above 20 mph.

LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION) #91-4-109
SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT - (SERVICE INFORMATION)
VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 10950849). The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life.
VEHICLES/COMPONENTS INVOLVED: ----------------------------- Some light duty trucks equipped with locking rear axles, RPO G80.
SERVICE PARTS INFORMATION:
Part Number Description ----------- ------------------ 10950849 Lubricant, Rear Axle (1 litre)
Parts are currently available through CANSPO.
WARRANTY INFORMATION:
As specified in Light Duty Truck Maintenance Schedules, locking rear axle fluid drain and refill is required owner maintenance at the first engine oil change. Failure to drain and refill the rear axle as specified may contribute to a later axle chatter condition. Refer to the appropriate Light Duty Truck Maintenance Schedule or service manual, section OB, for further details on change intervals.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.
© Copyright General Motors Corporation. All Rights Reserved.
________________________________________

Document ID # 518501
1992 Chevrolet/Geo Chevy K Pickup - 4WD

 
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