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  1. #1

    Default limited slip differential

    I have a question about what differential oil and additives I should put in them. I have the G80 limited slip diff and don't know what additive to put In the front and back. I have 75w90 synthetic I will be putting in the back and 80w90 synthetic in the front. i also notice that in my repair manual is telling me to fill them only to about 5/8 to 1 5/8 inches. is this true or can i just fill it until the oil is even with the plug?

  2. #2

    Default

    Regarding "I have the G80 limited slip diff and don't know what additive to put In the front and back" Below is a G.M. Service Information on Additive's with the G80


    G.M.(SERVICE INFORMATION) #91-4-109:
    SUBJECT: LOCKING DIFFERENTIAL (G80) LUBRICANT -
    VEHICLES AFFECTED:
    ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS,


    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)

    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.
    Last edited by 99'HEARTBEAT; 08-04-2013 at 05:56 PM. Reason: Added Infor.

    MIKE


    99"SILVERADO
    5.3 l 3.73 l G80
    BLACK BEAR CUSTOM TUNE
    SNUGTOP l COLORMATCH l KATZKIN










  3. #3

    Default

    Quote Originally Posted by newcheylover View Post
    I have a question about what differential oil and additives I should put in them. I have the G80 limited slip diff and don't know what additive to put In the front and back. I have 75w90 synthetic I will be putting in the back and 80w90 synthetic in the front. i also notice that in my repair manual is telling me to fill them only to about 5/8 to 1 5/8 inches. is this true or can i just fill it until the oil is even with the plug?
    I've always filled them to the plug with 0 issues.
    Last edited by BurbanMan; 08-04-2013 at 06:46 PM.
    Chuckie!!!


  4. #4

    Default

    The "old school" test was to stick your baby finger into the hole, if it come out wet, there was sufficient lub.
    Ray

    '09 Avalanche LTZ - Black
    '05 Envoy XL (sold)

  5. #5

    Default

    Quote Originally Posted by RayVoy View Post
    The "old school" test was to stick your baby finger into the hole, if it come out wet, there was sufficient lub.
    That's the way I learned it - has worked for me for 50+ years - yes, I'm "old school"

  6. #6

    Default

    Quote Originally Posted by grampy View Post
    - yes, I'm "old school"
    That's two of us @grampy

  7. #7
    Legend

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    Default

    when the weather is warm/hot filling to the point of the gear oil flowing out the plug is OK.

    when its cold the gear oil does expand a good amount this is where you would fill to 1/2 inch below the fill plug. this is not something to be overly concerned about. I would however check after running the vehicle , to be sure it is properly filled. sometimes it will drop some after use age.[air pocket].

    with the rear diff make sure the cover is removed and the debis is cleaned with mineral spirits and a cloth.also the cover magnet. then check the gears for cracks/pits.

    if you do not remove the cover it just shortens the life of the bearing/pinion etc.

  8. #8

    Default

    Quote Originally Posted by newcheylover View Post
    I have a question about what differential oil and additives I should put in them. I have the G80 limited slip diff and don't know what additive to put In the front and back. I have 75w90 synthetic I will be putting in the back and 80w90 synthetic in the front. i also notice that in my repair manual is telling me to fill them only to about 5/8 to 1 5/8 inches. is this true or can i just fill it until the oil is even with the plug?
    There is a common misconception that the G80 is a limited slip differential, it is not. The G80 is a locking differential. The G80 requires no additive in the fluid.

    If you are going to change the fluid in the rear differential, simply use Mobil 1 75W-90.

    I have always filled gearboxes with a check plug until the fluid comes running out of the fill hole.

    2013 Silverado LTZ White Diamond Crew Cab


    Mods:
    Advent OGM1 Navigation
    Husky Liners GearBox Underseat Storage
    Airaid MIT
    EGR Rail Caps
    K&N Air Filter
    Flowsound 40 Muffler
    Hypertech Max Energy Tune (only top end limiter removed and AFM disabled)
    Chrome Tailgate Handle Cover
    TonnoPro HF-155 Tonneau Cover
    WeatherTech Front and Rear Splash Guards
    Husky Liners X-Act Contour Floor Liners
    WeatherTech Side Window Deflectors

  9. #9

    Default

    Quote Originally Posted by stchman View Post
    There is a common misconception that the G80 is a limited slip differential, it is not. The G80 is a locking differential. .
    Actually stchman, there is a common misconception that the Eaton G80 is not a LSD diff. It is actually a LSD that operates as an open diff until there is a speed difference, between the axles, of 100rpm. At this point, the operation of the locking pawls turns the G80 into a posi rear-end. Granted, a posi that operates differently than a true posi rear-end, but it does have clutch packs to apply lock up torque to the axles.

    You are correct, additives do not need to be added, as long as the correct fluid is used.

  10. #10

    Default

    Quote Originally Posted by RayVoy View Post
    Actually stchman, there is a common misconception that the Eaton G80 is not a LSD diff. It is actually a LSD that operates as an open diff until there is a speed difference, between the axles, of 100rpm. At this point, the operation of the locking pawls turns the G80 into a posi rear-end. Granted, a posi that operates differently than a true posi rear-end, but it does have clutch packs to apply lock up torque to the axles.

    You are correct, additives do not need to be added, as long as the correct fluid is used.
    There are literally a million different opinions on what the an LSD and a ALD are. An LSD and an ALD use very different mechanisms to achieve applying power to both wheels.

    Now there are some that consider ALDs a type of LSD, but it appears that there is a LOT of opinion as to the difference between the two.

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