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Differentials, blood change

Discussion in 'The Garage' started by bugspray, Jan 22, 2004.

  1. bugspray

    bugspray 1/2 ton status

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    The search isn't working and I'm missing my manual. I need to change the gear oil in my axles. I've neglected doing it, and I've never done it. Am I right in thinking that I will have to take the whole cover off to drain it? Then I assume I will need to scrape the old gasket off, and put a new one on. I would also guess that it needs filled back up to the "plug".

    Is there a new cover I can get that has a drain and fill plug? I did some searches and it doesn't look like it.

    How often is it recommended to change it?

    What weight(s) would be good for Phx Az winter and summer's?
     
  2. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Any weight of gear oil works fine. I usually run 85W-140 in mine because my tranny is a little on the worn side and makes some noise so that's what I've usually got around the garage. This tranny is coming out so I'll probably start keeping the lighter stuff around after that.

    75W-90 or 80W-90 should be fine for you though.
     
  3. big pappa b

    big pappa b 3/4 ton status

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    As for the gaskets you can just use a RTV. A few after market diff covers hafve drain plugs but they are in the $150-200 range
     
  4. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Like mentioned, 80W90 is a good choice for diff fluid. I'll do a quick run-through of the process for you:

    1. Loosen off the diff cover bolts. You may have to pry the cover off with a screwdriver. Make sure you don't warp the diff cover getting it off.

    2. Let the old gear oil drain out.

    3. While the diff is draining do a really good job of scraping the old gasket/RTV off of both the diff cover and the face of diff. This is a crucial step: too much leftover junk on the mating faces and your diff will most certainly leak when you close it back up.

    4. Make sure you have some BrakeKleen on hand and after the diff is almost empty, liberally spray out the inside of the diff, making sure to get behind the R&P. You'll be amazed how much crap will rinse out that would otherwise have been left in the diff. FWIW, I use one can per diff.

    5. Take a cloth or rag and scoop out any leftover crud from the bottom of the diff.

    6. *IMPORTANT* - Make sure that you let the now-clean diff sit for a little bit so that any leftover BrakeKleen gets a chance to evaporate. If you leave any BrakeKleen in the diff, when you fill it back up with fresh oil the cleaner will break down the oil....

    7. Grab a tube of RTV and run a nice 1/4" bead around the mating face of the diff cover, making sure to circle each bolt hole. Let the RTV skin up for about a minute and then gently press it in place on the face of the diff. Some guys RTV the face of the diff too, but I've never had a leak doing the diff cover only.

    8. Bolt the sucker back on.

    9. Pop out the fill plug. On a 10 bolt rear it's on the top passenger side of the diff case. To take it out use a 3/8's ratchet with an extension. The 3/8's ratchet is a perfect fit for the plug.

    10. Fill up the diff with fresh oil. You'll know it's full when the oil starts to come out the fill hole.

    That's about it. Do the front the same way but take note that the fill plug is on the diff cover itself.

    Hope that helps, brother!!!! /forums/images/graemlins/thumb.gif
     
  5. bugspray

    bugspray 1/2 ton status

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    So it sounds like I don't need to pick up any gaskets then. How often is it recommended to change the gear oil?
     
  6. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Geez, I'm sure there's a suggested change interval, but I usually go by how the oil looks. The interval is gonna be alot longer if your truck's just a daily driver, like my 84. I usually pop out the fill plug every few months and see how the fluid looks and what the level is like. I generally do a full service every 30K or so.
     
  7. slider

    slider 1/2 ton status

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    Heres a tip, Always make sure the fill plug will come out before you drain out the old fluid. It kinds sucks filling the differential by using the vent tube. We had a truck come into the shop that the plug was rounded off, sure glad I looked at it before I started. I welded a bolt to the female plug so I could get it out. /forums/images/graemlins/truck.gif
     
  8. Pookster

    Pookster 1/2 ton status

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    Mine is rusted shut- The mechanics tried to get it loose, they just rounded the whole thing. I now have to do it by my vent tube-. Which hasnt been too bad acutally, I've done it twice now, doesnt take more than a few min (if its not too cold out!)

    I change mine when it gets dirty- since I tow and do occassionally pass through some deep water, I just make it a habit to change it every fall before it gets too cold. I have the vent tube routed all the way up the cab anyways, so water getting in itsnt a high likely hood.

    On my front, i attached a small segment of clear tubing, and had it sit lower than the top part of the vent for the diff. This way, it works like a sink trap- if any water got into it (or diff fluid got out), I can immediately see whats going on.
     
  9. K5MONSTERCHEV

    K5MONSTERCHEV 1/2 ton status

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    [ QUOTE ]
    Any weight of gear oil works fine. I usually run 85W-140 in mine because my tranny is a little on the worn side and makes some noise so that's what I've usually got around the garage.

    [/ QUOTE ]

    You should use MTF then.
     
  10. 4by4bygod

    4by4bygod 1/2 ton status

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    <<Is there a new cover I can get that has a drain and fill plug? I did some searches and it doesn't look like it.>>

    I just picked one up from summit racing, part number TRD - 8780.. it's for the 10 bolt rear in my 87. A company called TD performance products makes it. According to the chart on the box, it's good for other years too. The number for the summit store in sparks NV is 775-352-8787

    Tom /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif
     
  11. R72K5

    R72K5 Banned

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    you will want thicker oil 80/90w normal stuff, i wouldnt go with the other stuff, if you have G80 in eithe rof the axles then go to chevy parts counter and get positraction fluid additive form them its 7 a bottle here,

    before you start pulling cover bolts make sure that you can get diff case [plug broken loose that you use to fill diff with, it is on the side of the diff and takes a 3/8" ratched drive, use some heat a little and some candle wax to penetrate the threads

    your owners manual will tell you hoe much fluidf the diffs hold on rtefill, and you can use rubber hose on bottle top to fill with, as much length as you need if you hold the bottle in a good way under there, or get one of those metal can oil squirters, but that probavbly would take longer

    and i use caulk on both sides of the new gasket and carb cleaner to clean the surfaces first, then you will never have a leak ever.

    while you are in there you cn add a strong magnet to bottom of diff housing in there and make sure tooth cvontact wear pattern is ok and thast ther eis no metal in fluid orlaying in case
    \
    i think 30k miles or 50k miles is when to change diff oil but no one ever does, some are real bad dirty thanks to that

    good luck
     
  12. bugspray

    bugspray 1/2 ton status

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    What's the positrac fluid for? Also did I understand right to put a strong magnet ont the bottom of the housing-inside of it?

    Does anyone know what the foot pds of torque the bolts take? I heard if you tighten them too much, it will cause the leaks.
     
  13. supersize75

    supersize75 1/2 ton status

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    Just make them snug, like valve covers, not to much or it will leak. /forums/images/graemlins/thumb.gif


    and I agree with the break cleaner, very good advice there /forums/images/graemlins/thumb.gif
     
  14. Executioner

    Executioner 1/2 ton status

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    " if you have G80 in eithe rof the axles then go to chevy parts counter and get positraction fluid additive form them its 7 a bottle here, "

    Are you for sure, or are you just guessing ?
     

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