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Rear end leak

This is a discussion on Rear end leak within the Drivetrain forums, part of the LSx Technical Help Section category; I changed my gear oil last week (biggest mistake i ever made) and I used the rtv gasket maker instead ...

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    Senior Member Rhinohuey's Avatar
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    Rear end leak

    I changed my gear oil last week (biggest mistake i ever made) and I used the rtv gasket maker instead of a gasket. I followed the instructions on the tube but when I torqued it down to 22 ft-lbs (think thats correct) all the rtv just squished out around the cover. I figured it would be ok and went ahead and added my ls additive and gear oil, took it for a spin, got back and it was leaking like a son of a bitch.

    So I went and bought the Felpro paper gasket, rtv'd both sides put it all back together, torqued it down and realized the gasket and rtv was squishing all back out the sides. So I took it all back apart and it looked like the gasket exploded into about 10 different pieces.

    So I try again with just the rtv being extra careful to make it the same shape as the housing mounting surface and put all the oil back in. I though it was all good until I came back from school this weekend and there was a big ol puddle of gear oil on the ground.

    So my dad gives it a shot today with the paper gasket and rtv on both sides and the stupid gasket tears in about 6 places again.

    Am I the only one that cant change the fucking gear oil without getting into a project over my head??

    I also tried to find a rubber gasket like the stock one but no autoparts stores sell one. Am I gonna have to go spend next weeks check at the dealership on one?

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    Sounds like you are using too much RTV. Just a thin bead will do if you are using a gasket -- helps to hold it in place and usually best if you spread it out to thinly coat the surface. Without a gasket -- also don't overdo it and maybe let it set up just a bit before you install the cover. Are your surfaces good and clean? Throw a shop rag over your gears and hit it brake cleaner, or, use denatured alcholol on a rag to wipe it down.

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    Senior Member Rhinohuey's Avatar
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    yeah when I did it I put about a 1/8" or 3/16" bead. When my dad did it he spread a thin coat all over both sides of the gasket. And yes, both surface are very clean.

    Once I followed the instructions on the tube and put the cover on just a couple minutes after applying the rtv and only finger tightened it. Then after an hour I tightened it a couple turns. Then I waited for it to completely set up before I torqued it down but it still just all squished out.

    Another time I applied the bead, waited for it to completely set up before installing...same thing.

    22 ft-lbs is spec right?

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    Member km346's Avatar
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    Quote Originally Posted by Rhinohuey View Post
    yeah when I did it I put about a 1/8" or 3/16" bead. When my dad did it he spread a thin coat all over both sides of the gasket. And yes, both surface are very clean.

    Once I followed the instructions on the tube and put the cover on just a couple minutes after applying the rtv and only finger tightened it. Then after an hour I tightened it a couple turns. Then I waited for it to completely set up before I torqued it down but it still just all squished out.

    Another time I applied the bead, waited for it to completely set up before installing...same thing.

    22 ft-lbs is spec right?

    hmm as long as both surfaces are clean you shouldn't have a problem... ive used the gasket and just rtv in past changes and never sprung a leak and ive honestly never torqued my cover bolts, just snugged them with maybe an additional 1/8-1/4 turn.

    Is your cover bent at all? the factory cover is only stamped steal, i could see it warping easily...
    Last edited by km346; 03-23-2009 at 09:40 AM.

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    Something Diabolical... chuckie669's Avatar
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    2000 C5 Torch Red

    When I did mine I just ran a bead like the pic below and let it set for an hour before installing / tightening.


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    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Personally I hate RTV sealant. I never use that stuff on anything. Brush on permatex is what I use. Clean mateing surfaces with brake cleaner on a rag. brush on the permatex on all the mateing surfaces and on the gasket replace the cover "dont over tighten" snug then down in a cross pattern till they are tight but not too tight. Good luck...

    Also make sure the axle "breather" is not pluged. A pluged up breather can cause it to leak.
    Last edited by Smittro; 03-23-2009 at 12:38 PM.

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    Senior Member Rhinohuey's Avatar
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    Quote Originally Posted by Smittro View Post
    Personally I hate RTV sealant. I never use that stuff on anything. Brush on permatex is what I use. Clean mateing surfaces with brake cleaner on a rag. brush on the permatex on all the mateing surfaces and on the gasket replace the cover "dont over tighten" snug then down in a cross pattern till they are tight but not too tight. Good luck...

    Also make sure the axle "breather" is not pluged. A pluged up breather can cause it to leak.
    whats is the breather? ive never heard of that before

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    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Quote Originally Posted by Rhinohuey View Post
    whats is the breather? ive never heard of that before
    it's usually a little tube, or a very small plastic peice with like a loose cap on it at the top of the axle housing this allows preasure from heat buildup to escape.Almost always above the dif section of the axle housing. Usually somewhere near the highest point on the dif portion of the axle housing. Pickups sometimes have a peice of rubber hose attached to it and goes up and is clipped to the frame. On trucks this helps keep water out of the axle. If the housing is covered with crap from the road it's sometimes harder to find on cars but I'm still willing to bet it has one. Axle "breathers" have been used pretty much since "live" axles came out.hope this helps.
    Last edited by Smittro; 03-23-2009 at 04:34 PM.

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    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Best way to see the breather is to raise the body and let the axle "hang" then you can get in and look at it to inspect for clogging. However the plasic sometimes used in some of the "breathers" tends to become brittle over time and can easily be broken off. Leaving almost no evidence of a "breather" This is the reason for "hanging" the axle to inspect it. If pressure cant get out then it tends to find a weak spot. Such as outer seals of the axle, or the "pumpkin" cover gasket gives way. Either way = a mess. Best ways to clean it out is to either remove it and replace, or if (only a tube exsists) run a piece of wire through it from the inside out. So not to contaminate the gear oil thats always left behind when changing it. Hope this helps.
    Last edited by Smittro; 03-23-2009 at 04:59 PM.

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    Senior Member Orcus79's Avatar
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    Sounds like you are way over tourqing the bolts there. Both surfaces have to be clean of any debris and flat. Yeap 22ft/lbs is right and tightened in a criss cross pattern. Are you using an accurate torque wrench?

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    Senior Member Rhinohuey's Avatar
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    Quote Originally Posted by Orcus79 View Post
    Sounds like you are way over tourqing the bolts there. Both surfaces have to be clean of any debris and flat. Yeap 22ft/lbs is right and tightened in a criss cross pattern. Are you using an accurate torque wrench?
    Ummm...an accurate from Walmart. Do you think its possible I could be over torquing them that much? I don't really know what 22ft/lbs feels like.

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    ʢ ൧ ൨ ൩ ൪ ൫ ൬ ൭ ൮Ր Ց Ւ Փ Smittro's Avatar
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    Quote Originally Posted by Rhinohuey View Post
    Ummm...an accurate from Walmart. Do you think its possible I could be over torquing them that much? I don't really know what 22ft/lbs feels like.
    It's possible, but I think it's more likely that rtv is causeing the gasket to shift and tear as you're torquing them down. Permatex is the way to go in my oppy. Also like I was sayin' earler tighten them down in cross pattern. Over tightening can cause the gasket to crap out but I dont really think you are. good luck!

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    Life in the Fast lane sunsetorangess's Avatar
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    I use RTV everyday, some people hate it some people love it, i did a couple of diff's in the past few days, Just ensure both sides are clean and free of old gasket. then apply a thin bead of rtv around both sides of the gasket, like the picture above shows.
    tighten it all down and should be good to go. Is it leaking from the same spot everytime? Or is it picking different spots to leak from? when you were removing the old gasket did you knick or gouge the cover?
    J
    2001 SS, Its not the car its the Driver that matters....

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    Senior Member Rhinohuey's Avatar
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    I've given up on the gasket....every time I try it it just breaks into a bunch of pieces when I tighten it down. And the leak always just seems to be the whole bottom of the cover. I put the rtv on, let it set up, tighten it down, add fluid, (seems fine) and then after driving it and after the fluid has been in it a few hours the whole bottom where the rtv is kinda squishing out is wet and the rtv is soggy almost....and before I know it a drip is forming.

    I never thought I was gonna have this much trouble with something so simple...I guess I'll just try again maybe with a thinner bead of rtv and not torque all the way to 22 this time.

  15. #15
    Something Diabolical... chuckie669's Avatar
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    Did you have this problem before changing?
    Is it coming out when your not running?
    Also, is it from around the bolts or just on the bottom?

    Pop the side fill out on a level ground and see if it's dripping out (could it be overfilled).

    Also, mine leaks from where the driveshaft joins the rear end and when driving it blows it back by the cover giving the appearance of a leaky cover.

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    That guy thearborbarber's Avatar
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    This is what my mechanic uses on diff covers. No gasket.

    http://www.permatex.com/products/Aut...sket_Maker.htm

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    Senior Member Orcus79's Avatar
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    This begs the question, are you using the right RTV, You need to use the black stuff rated for oil. Sounds like it is reacting to the heat and oil almost.

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    Senior Member Rhinohuey's Avatar
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    yeah i believe the oil is causing it also....like its make the rtv soft.

    And I'm using the red rtv...the high heat stuff like they said on install university. Is that the wrong stuff?

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    Senior Member Orcus79's Avatar
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    I dunno if it is the wrong stuff, but I have never used it for anything. You do have to read the labels, some are not compatable with oils. I suggest getting the black stuff, that is also high temp.

    What chemicles are you using to clean the gasket surface?

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    Quote Originally Posted by thearborbarber View Post
    This is what my mechanic uses on diff covers. No gasket.

    http://www.permatex.com/products/Aut...sket_Maker.htm
    Yep Permatex makes good stuff I use their products too, and have used Hi-tack spray on, dont remember who makes it though.
    Last edited by Smittro; 03-25-2009 at 11:38 PM.

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