Differential Refill Fluid Levels?

[EddieC]

On '08 Tahoe, what's the appropriate refill fluid level on the front and G80 locking 10 bolt rear differentials?
Is level with the bottoms of the drain holes appropriate?

Does the spec'd GM 75w-90 Synthetic #89021677 fluid (spec 9986115) have friction additive for the locker or does it need it added? The fluid number is from the Owners Manual and there is no mention of friction modifier additive, but on the same note there are no fluid quantities listed either so the manual may be lacking.

 

[Doubeleive]

yes level with the fill hole, additive is not needed, some add it anyway up to you
specific fluid amounts are listed in the owners manual

 

[PG01]

Look in capacities, it’s there...this is for my ‘13

 

[EddieC]

I found this that answers the question from GM:

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.

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.

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.

 

[EddieC]

Interesting Galante.
My owner's manual call for the same rear lube number but the front is 89021672, not .....71.

 

[gooffeyguy]

Look in capacities, it’s there...this is for my ‘13
View attachment 250246 View attachment 250247

I don't see the front/rear differential capacities listed, only type/part number

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[Doubeleive]

I don't see the front/rear differential capacities listed, only type/part number

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diff's just get filled to the fill line, I thought it listed capacity but it doesn't but it should be around 2.3 or 2.5 qt.

 

[Bob2C]

I found this handy


https://www.fluidcapacity.com/


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[swathdiver]

The front differential takes 1.51 Quarts, the rear 8.6 (that most everyone has) takes 2.15 Quarts. To the fill line or just a little under is fine to properly lubricate it.

 

[EddieC]

The front differential takes 1.51 Quarts, the rear 8.6 (that most everyone has) takes 2.15 Quarts. To the fill line or just a little under is fine to properly lubricate it.

What fill line? I haven't talked to superman in ages.
What I found was .04" to .75" below the bottom of the fill hole for the rear and 0" to .125" below for the front, so basically filling and letting it dribble to the bottom of the hole works for me.