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Differential Issues and Other Noises

The automotive differential is designed to drive a pair of wheels while allowing them to rotate at different speeds.


Your Vehicles differential service place - The Shop in Alvin Tx

Driveline, Axle, Ring and Pinion Gear and Differential Noise


Noises, vibrations and other irregular driving characteristics can often help diagnose a differential or driveline problem. Here are a few typical symptoms and their possible cause:


  • Whirring noise only while decelerating at any or all speeds is most likely caused by bad pinion bearings or loose pinion bearing preload, and almost never by bad ring and pinion gears.
  • A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears or improper gear set up.
  • Rumbling or whirring at speeds over about 20 mph can be caused by worn carrier bearings. The noise may change while turning.
  • Regular clunking every few feet may indicate broken ring or pinion gears.
  • Banging or clunking only on corners can be caused by broken spider gears, lack of sufficient positraction lubrication, or worn positraction clutches.
  • Rumble while turning may indicate bad wheel bearings.
  • A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft.
  • Clunking only when starting to move or getting on and off the gas might be loose yokes, bad u-joints or worn transfer case or transmission parts.


How the Rear Differential Works


One of the most important things about a rear differential is how it operates around corners. It uses side gears or spider gears for cornering.

When a vehicle turns into a curve or goes around even a slight bend the wheels on the outside have to travel a greater distance than the wheels that are tracking on the inside.

If it wasn’t for this situation the two axles could just be linked together and everybody would have a positraction rear end. The operation of the spider gears allows for the rear wheels to turn at different speeds when cornering. This also provides beneficial handling characteristics.


Noise from Rear Differentials


Where this knowledge comes in handy is for noise diagnosis. If your vehicle only makes noise or has a problem when cornering then the inspection of the spider gears or often called side gears should be performed.

If there is no noise when the vehicle is traveling straight-ahead the ring and pinion gears and their associated bearings are probably not having a problem. In the case of an automatic positive traction type differential such as the one on a 2004 Chevrolet blazer, noise diagnosis can be further complicated.

These types of rear ends have a clutch pack that transfers power to the wheel with the most traction. When the wheels are not slipping this clutch should be released and allow the vehicle to corner normally.

Problems with the clutch pack can be mistaken for problems with the side gears or spider gears. Also in the lubrication fluid the General Motors positraction unit has a special additive to prevent sticking operation of the clutches.

If regular gear oil is installed in a positraction unit with no special additive, grabbing, jerking and noise can occur around corners. Check the auto repair manual for your specific vehicle to make sure you have the correct fluid installed in the rear differential.


Positractions & Limited Slips:


Limited Slip - Differential Repair in Brazoria county - Alvin Tx The Shop
Posis and limited slips transmit equal torque to both wheels when driving straight. However, when one wheel spins due to loss of traction, a patch of ice, mud, too much throttle, etc., the unit automatically provides more torque to the wheel that has traction. Recommended for daily driving, works well in ice, rain, mud and snow. However, in situations where absolute lockup is needed, a limited slip is not the best choice due to the fact that limited slips do slip in some situations.

Positraction is a type of limited slip. The name “positraction” was used by General Motors for their limited slip differential and the name has been associated with limited slips for many years.


Limited Slip - Differential Repair in Brazoria county - Alvin Tx The Shop


Automatic Lockers:

Lockers Differential Repair in Brazoria county - Alvin Tx The Shop
Lockers (mechanical locking differentials) provide 100% transfer of power to both drive wheels. This power can be lost if both wheels spin, but a locking differential will never let one wheel spin free by itself while the other one sits still (unless the unit is broken). Automatic locking differentials are engineered to keep both wheels in a constant drive mode, yet have the ability to unlock to permit a difference in wheel speed while negotiating turns.





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