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Differential Fluid

Differential Fluid

Postby D-Wat [OP] » Feb 26 2013, 2:23pm

So I am planning on changing my front and rear diff fluid along with transfer case this weekend. I went to the local autozone to pick up some 75W-90 synthetic gear oil. I have read that with my G80 locker I don't need any additives. I was looking between 2 different brands: mobil 1 synthetic, and valvoline synthetic. My question is on the mobil 1 bottle the letters LS were on there and I was thinking that meant limited slip, the valvoline had limited slip on the bottle also. Is this gear oil ok to put into my differential or do I need to find some synthetic gear oil that doesn't say LS or Limited Slip?
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Related Topics  is changing differential fluid important?   Differential and transmission fluid change   Problem After Rear Differential Fluid Change   Differential question   Differential Noise   differential size?   Differential Locker - What do I need   Differential seeping?   new rear differential   Differential cover   G80 DIFFERENTIAL PROBLEM   differential howl question   Rear Differential Gasket   Rear Differential Positraction 
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Re: Differential Fluid

Postby red16red16 is online! » Feb 26 2013, 2:45pm

I have been running Mobile 1 with LS for a couple years in my 2500 with a G80,and it works great.
Amazed how good it works in the snow,and gravel hillclimbing.Just ease on the throttle,and it locks,and away we go.People that complain how it works,just do not use the throttle correctly.I have touched the brakes lightly to stop the wheelspin,and it will lock right up.
If you like to do burnouts on pavement,you will break your G80.
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Re: Differential Fluid

Postby D-Wat [OP] » Feb 26 2013, 3:17pm

Ok. Thank you. I just wanted some clarification that that oil was ok to put in my pickup.
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Re: Differential Fluid

Postby steved » Feb 26 2013, 3:42pm

I have looked at that "no LSD modifier required" statement several times...here's my take.

I believe its meant to tell the consumer that additional additive is not required above and beyond that which is already found in gear oil. Too much LSD additive is not a good thing. And regardless off what anyone wants to believe; any LSD with clutches (which describes a G80 "locker") needs some LSD additive or the clutches will chatter.

My last truck had the same statement in the owners manual, and as soon as I changed fluid the diff started chattering (feels like two blocks of rubber slipping past one another)...adding a bottle of modifier cured it. You will be hard pressed to find a gear oil that isn't fortified with LSD additive.
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Re: Differential Fluid

Postby Z15Z15 is online! » Feb 26 2013, 3:59pm

Sorry but I have to disagree with some of the info in the last post. The Limited Slip Additive is made for a Limited Slip Differential ONLY. Its sole purpose is prevent noise.

Limited Slip differentials are preferred in Performance cars because as the name implies they allow Limited Slip. The G80 locker does not. Its when the limited slip slips that is can cause chatter (noise) and the additives is designed to eliminate that noise. Using that additive (which is not designed to be used in a Locker) can cause the locking mechanism to not function (per GM).

I am not making this up, this info comes right from GM. All light duty trucks and SUV's built in the last 20 yrs use a G80 locking differential except for the Quadrasteer models which use a Dana rear axle and was limited slip primarily because Eaton has the market cornered.

Also note, don't confuse gear lubes that say suitable for use in limited slip differentials with the additive, the are different. You likely won't ever find a synthetic gear lube that will not say, suitable for limited slip. Different chemistries

#PIP4054D: Eaton Locking Differential Chatter Shudder Noise On Turns - (Jul 19, 2010)


Subject: Eaton Locking Differential Chatter Shudder Noise on Turns


Models: 2004-2007 Buick Rainier

2000-2011 Cadillac Escalade, ESV, EXT

2002-2011 Chevrolet Avalanche

2004-2011 Chevrolet Colorado

2003-2009 Chevrolet Express

2000-2011 Chevrolet Suburban, Tahoe

2000-2007 Chevrolet Silverado Classic

2007-2011 Chevrolet Silverado

2002-2009 Chevrolet Trailblazer

2004-2011 GMC Canyon

2002-2009 GMC Envoy

2000-2011 GMC Yukon, Yukon Denali, Yukon XL

2000-2007 GMC Sierra Classic

2007-2011 GMC Sierra

2003-2011 GMC Savana

Equipped With a Locking Rear Differential RPO G80
--------------------------------------------------------------------------------

This PI was superseded to update model years. Please discard PIP4054C.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:
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.

Notice: This does not apply to vehicles equipped with RPO QS4 (Quadrasteer) which is part of option package NYS. Quadrasteer vehicles use Dana axles and have a different fluid requirement.

Notice: This PI does not apply to vehicles equipped with a RPO G86 limited slip differential.

Recommendation/Instructions:
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, use the fluid part number listed in SI for the vehicle currently being worked on. If the condition returns, replace the rear differential clutch This PI was superseded to update model years. Please discard PIP4054C. plates and refill the differential with new synthetic fluid, use the fluid part number listed in SI for the vehicle currently being worked on. Refer to eSI for clutch plate replacement and set up procedures.

Notice: Eaton locking differentials used in 10.5 rear axles are equipped with steel clutch plates. It is a design characteristic of these steel clutch plates to exhibit more clutch chatter than other models.

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.

Notice: On Quadrasteer equipped vehicles, simply flush the rear axle and refill with the fluid listed in SI document 793720 under the steerable application.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these 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
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Re: Differential Fluid

Postby masterem88 » Feb 26 2013, 4:33pm

to put it simple if its a locker (mechanical) use straight gear lube in the weight manufacterer recommends or aftermarket carrier recommends. If you have a limited slip ( with a clutch pack in the carrier) use a limited slip gear lube or straight gear lube with a bottle of limited slip additive. I find using straight gear lube with a bottle of motorcraft friction modifier to work best. Its no different that transmission clutches and trans fluid already has a small amount of friction modifier made into it for this same purpose. You do not want to use alimited limited slip gear lube with a mechanical locker. It will cause inoperation of locker or not releasing at times. Every locker ive ever installed i love the instructions in big bold letters says do not use friction modifier with this carrier or incorrect operation will occur and warranty void
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Re: Differential Fluid

Postby masterem88 » Feb 26 2013, 4:36pm

Friction modifier is for the clutches only. It serves no other purpose for the rest of the differential parts
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Re: Differential Fluid

Postby Z15Z15 is online! » Feb 26 2013, 4:47pm

Note - Just because a gear says it suitable or compatiable for use in a limited slip differentials is no indication is has the limited slip additive. Different additives can accomplish the same function and still not have deterimental effect on the lockers.

I have the AMSOIL Severe Gear 75W-90 in both the G80 limited slip in my CTS and in the locker in my Denali. The CTS posi does not chatter one bit and I did not put an additive in with it. Nor in my Denali.

re:
AMSOIL Severe Gear is compatible with most limited-slip differentials. If limited-slip differential chatter occurs, add AMSOIL Slip-Lock friction modifier additive.
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Re: Differential Fluid

Postby steved » Feb 26 2013, 5:08pm

None of you can read an illustrated parts diagram can you?

The G80 is not a mechanical locking differential (e.g. Detroit Locker). The G80 is nothing more than a fancy LSD. Period. It has clutches, acts as a LSD under normal operation, and has the ability to add load to the clutches to cause them to essentially "lock". It is really no different than a Dana Power-Loc.

Further, show me where the GM fluid specifically states "contains no LSD modifier" on the bottle. I'll lay odds it does have LSD modifier as part of its make up.

I have torn G80s apart that have grenaded and, other than the engagement pawl that forces the clutches together; there is not one gear-on-gear or tooth-on-tooth direct drive link in them. That's why they "wear out"...the clutch friction materials wear out and then there is nothing to grip...a true locker wouldn't "wear out".

Have a nice day. :lol:
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Re: Differential Fluid

Postby steved » Feb 26 2013, 5:13pm

And further, if adding LSD modifier was an issue then Mobil LS (and most any gear oil, including Amsoil) would cause issues...Mobil LS seems to work just fine in my truck, and seems to work for a lot of other folks.
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