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Rear Diff Fluid Change

Discussion in 'Chevy Trucks' started by Newdude, Oct 30, 2009.

  1. Newdude

    Newdude Senior Member
    Messages: 878

    Ok. I am doing a fluid change on my rear diff, front diff, and t-case tomorrow.
    Couple Questions:

    I have the 11.5" rear, G80. Does the pan need to be removed to drain the fluid?

    If I do remove the pan, do I have to purchase new cover bolts?

    If I read GM Service Info correctly, the front diff. has both a drain and fill plug. True?
     
  2. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    No need to remove the rear cover, there's a drain on the bottom of the housing. Convenient. :drinkup:

    The front diff will have both a fill and drain plug, both located on the driver side. Fill will take a 15 MM, drain will be a 13 MM.
     
  3. Newdude

    Newdude Senior Member
    Messages: 878


    B&B strikes again!! Thanks very much! Now, one more question. Owners manual states to fill the rear 1/2 an inch to 0 from the fill hole. Roughly how many qts would that be? Same ? for the front too.
     
  4. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Takes a little over 4 qts to fill the rear and a little over 3 for the front.
     
  5. Newdude

    Newdude Senior Member
    Messages: 878

    Cool and thanks!

    EDIT: One final question. I purchased Mobil synthetic gear oil. Would a locking/limit slip additive need to be added? I would have bought the GM stuff, but its $36 a qt!
     
    Last edited: Oct 30, 2009
  6. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    GM doesn't recommend adding any friction modifiers to the G80 equipped axles when using the correct fluid but I've had to on a small percentage in the past as an effort to smooth them out as the G80's can be harsh in their locking/unlocking at times.

    I wouldn't add any initially, but if you later begin to experience any excessive harshness from the diff then go in and add two bottles of modifier.
     
  7. Newdude

    Newdude Senior Member
    Messages: 878


    Gotcha and thanks again.
     
  8. mkwl

    mkwl 2000 Club Member
    Messages: 2,361

    Does anyone have good methods to add fluid to the font diff? I don't see any way to get a bottle in there to fill it up.
     
  9. Newdude

    Newdude Senior Member
    Messages: 878

    Autozone and many other parts stores make hand pumps that I believe screw on to the bottle.
     
  10. mkwl

    mkwl 2000 Club Member
    Messages: 2,361

    Aaaahhh- what a handy thing to have!
     
  11. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    A long piece of rubber hose slipped over the nipple on the bottle works good in a pinch also.
     
  12. Newdude

    Newdude Senior Member
    Messages: 878


    Here is what I figured out after doing it today. If you use either a hand pump or a rubber hose over the nipple, the easiest way to get at both plugs is to remove the oil pan skid plate. The transfer case is fun too, especially with that crossmember in the way. :D :drinkup:
     
  13. tuney443

    tuney443 PlowSite.com Addict
    Messages: 1,847

    Without a pump or an extension flex tube with a funnel,if you have to squeeze it in the rear from the 1 qt. bottle,if you take off the spare,it's a whole lot easier.
     
  14. Newdude

    Newdude Senior Member
    Messages: 878


    Is that with the 10.5"? The 11.5" has a filler on the right side, midway up on the rear diff.
     
  15. BigLou80

    BigLou80 Senior Member
    Messages: 558

    what do you mean by harshness ? I usually don't notice mine until I have a load or a trailer then I can feel it trying to hop around corners
     
  16. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    That would be considered as a "normal" amount of harshness. When they want to drag them around every turn loaded or empty is when you consider it an excessive amount.
     
  17. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I bought one of those 8 dollar transfer pumps from Walmart. Two hoses, stick one in the bottle, one in whatever you are trying to fill. Works great, saves alot of work. And fluid too...