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2011 Chevy Suburban 2500 HD - Differential Fluid

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Hi, folks,


I have a 2011 Chevy Suburban 2500 HD, 6.0L gas.  RPO contains G80, GT4, L96.  This is my 1st post on the forum, and hope I’m posting in the right place. 


Could someone please help me with the rear axle/differential fluid? Owners manual 
states SAE75W-90 Synthetic Axle lube (GM#89021677, replaced by 88900401). It DOESN’T say anything about Limited-Slip Axle lubricant additive (GM #1052358, replaced by 88900330).  


However, as shown in the attached picture, ACDelco states the car NEED FRICTION MODIFIER w/LOCKING/LIMITED SLIP DIFFERENTIALS-USE ADDITIVE 88900330; Quantity varies by application.


How do you think please? Thanks and Happy Thanks Giving!


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From several forums where there have been threads on this, most people find "plain" 75W90 works fine, some people, for whatever reason, find the G80 chatters with using plain, and adding a bit of friction modifier makes it go away.


GM claims the G80 doesn't need it, I believe some people have found Eaton (who makes the G80) does want the friction modifier (as it does have a clutch).

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Its NOT a limited slip differential...


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


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

¨ 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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from GM service info....


Customers may comment on a chatter or shudder from the rear axle on vehicles equipped with an Eaton locking differential. This condition would be noticed in parking lot maneuvers, turning, or during locking differential engagement and may be more noticeable when the differential is hot. Locking differential clutch chatter may be causing this concern.

If differential clutch chatter is encountered in a vehicle equipped with an Eaton locking differential, flush, drain and refill the differential with new synthetic fluid. If the condition returns, replace the rear differential clutch plates and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on.

Important: Installing any friction modifier causes the clutch pack in the locking differential to slip and miss engagement. A fluid flush can often remove debris that is a contributor to clutch chatter. Adding friction modifier additive can cause a loss of locking differential functionality.



Chatter is essentially the build-up and release of energy between the differential clutch packs in a limited slip differential during operation. This phenomenon often occurs when torque is transferred between the clutches or when rotational speeds change. During the stick-slip phase, energy is built up to a point where contact between the clutch plates change between static friction (stick) and dynamic friction (slip), resulting in noticeable vibrations. It is this vibration that causes an audible chatter or ratcheting to be heard within the differential. While certainly an annoying characteristic, there is typically no mechanical damage occurring to the differential. It is most often noticed in parking lots or slow driving while turning where the outside wheel turns faster than the inside wheel.

In an effort to control this chatter, friction modifiers are often used. These additives result in a smoother transition between the two states of friction: static and dynamic. Static friction occurs when the clutches physically lock together, while dynamic friction occurs as the clutches are slipping, ergo Limited Slip Differential.


Edited by elcamino
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7 minutes ago, diyer2 said:

I have never used a friction modifier in a G80. Never had chatter. Changing it more often helps IMO.

It does not require a friction modifier.  

I plan to do the same for now, unless there’ are issues, then it won’t be too late to add friction modifier. Thanks!

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The GM "grapejuice" and the other major brands (I use Mobil 1 Synthetic Gear Lubricant LS 75W-90) already have the proper amount of friction modifiers for the G80.  Not enough, or too much, friction modifier will give you unsatisfactory results.  I can recommend the Mobil 1 since I've used it for 15 years (over 100k miles) now without any differential problems, or chatter, or other ill behavior or noise.

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