Will I know differential chattering when I hear it

[dgpretzel]

I changed the differential gear lube in my recently acquired '03 Astro from whatever it was to Amsoil. Didn't add any limited slip additive. Seems OK. Will I know chattering (indicating need for limited slip additive) if it occurs? Is it distinctive? Easily heard from inside? When does it happen-- when the limited slip is engaged? Or all the time?

Thank you.

DG

 

[JTK]

You will feel it more than hear it. It's kind of a driving over a rumble strip type feeling, felt mostly during tight turns.

Joel

 

[dgpretzel]

Thank you.

DG

 

[Mike_dup1]

fyi
Note-Disregard the lube parts numbers as they have been replaced with newer part numbers.

Quote:

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LOCKING DIFFERENTIAL LUBRICANT (SERVICE INFORMATION)
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.

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[dgpretzel]

OK. G80-- that's me.

Thank you.

DG

 

[CBODY67]

The distinction between G80 axles -- "limited slip" and "locking". Same function and same option code, but different ways of going about it AND different lube needs.

CBODY67

 

[dgpretzel]

I don't think I fully understand...

I think I get the difference between "limited slip" and "locking". But, I'm not sure what you are saying about the G80 axles. Are you saying that not all G80's are the GOV-LOC devices? That, in fact, sometimes "G80" denotes "limited slip" and sometimes "locking"? How can I tell the difference?

Thank you.

DG

 

[dgpretzel]

P.S. It would seem to me that the GM document quoted in an earlier post indicates that "G80" means "locking".

But, what do I know?

DG

 

[Ken2]

The only differentials that need the LS additive are those with clutch-type limited slip. A locking differential does not need the additive, nor does a torsen. In any case, just about every differential gear oil these days already contains the additive, and more is not better. In a differential with clutches and the gear oil says that it is suitable for limited slip, don't add more additive unless you get chattering. Then add 1/4 tube at a time.


Ken

 

[Mike_dup1]

One more time.

They are both the same option code
G80 Limited slip differential is in cars
G80 Locking differential is in trucks

from the CTS order guide
(G80) limited slip differential
from the GMC truck order guide
(G80) heavy-duty automatic locking differential


I have both, my 2004 GMC Z71 has the locker and my 2005 Cadillac CTS has the limited slip.



The locker provides better traction which trucks often require.

 

[dgpretzel]

Quote:

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One more time.

They are both the same option code
G80 Limited slip differential is in cars
G80 Locking differential is in trucks

from the CTS order guide
(G80) limited slip differential
from the GMC truck order guide
(G80) heavy-duty automatic locking differential


I have both, my 2004 GMC Z71 has the locker and my 2005 Cadillac CTS has the limited slip.



The locker provides better traction which trucks often require.

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OK. But, if G80 can mean either locking or limited slip, how can I tell which I have?

I own a 2003 Chev Astro. I'm guessing that, unlike most other minivans, it may be more "truck" than "car". But, how do I tell for sure?

Thank you.

DG

 

[Mike_dup1]

Rear wheel drive vans are not considered cars. Its a truck and should have a locker.

What does the owners manual call it? That should give a clue.

Quote:

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G - 80 Option - Eaton Locking Differentials

Availability

¨ Standard Equipment on Dual Wheel 3500 Series trucks.

¨ Optional Equipment (G80 Order Code) on all GM two-wheel and four-wheel drive light trucks and sport utilities.
Benefits

¨ Improved traction differentiates the vehicle relative to other rear wheel and four-wheel drive vehicles on the market.

¨ Functions as a limited slip differential during normal driving conditions; provides full axle lock when needed.

¨ Maintenance free; requires no lube additives.

¨ Enhanced towing and off-road performance.

¨ Patented carbon friction disc technology enhances performance and durability while reducing warranty claims.
Principles of Operation

¨ Wheel speed difference (left to right) in excess of 100 RPM will cause a flyweight mechanism to open and catch a latching bracket.

¨ The stopped flyweight will trigger a self-energizing clutch system, which results in the cam plate ramping against a side gear.

¨ Ramping increases until both axles turn at the same speed (full lock), which prevents further wheel slip.

¨ At speeds above 20MPH, the latching bracket swings away from the governor and prevents lockup from occurring.
Technical Specifications

¨ Automatic locking takes place within a fraction of a second, so smoothly that it is unnoticed by the average driver.

¨ Unlocking occurs automatically, once the need for improved traction is gone, and is unnoticeable to the average driver.

¨ Compatible with anti-lock brake systems.

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[WishIhadatruck]

I have a 1996 Buick Roadmaster with a G80 limited slip. My owners manual tell what kind of fluid to use and it also says to add the limited slip additive. If you need the additive I would suspect your owners manual would say so. Find where it says what fluid to use when changing the rear diff. and if you find no mention of using an additive then I would assume you don't need to.