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  1. #1
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    Default A few winter Jobs

    With winter approaching I plan to sort out a few of the oil leaks I've been ignoring on my '81.

    First is from the engine. I believe it is the rear main seal causing the leak. (engine oil on the bell housing) Since I've got the pan off I'll do the Pan gasket at the same time. Anything else I should look at while I'm in there?

    Second is the diff. I believe I have a leaking pinion seal, there is always oil everywhere around the front of the diff. Can this be done without removing the diff from the car? (I think I saw a thread on this but can't find it now) I'll also do the front bush at the same time and check the U-joints. Anything else I should look at? The rest of the rear suspension was done not long ago.

    If I can get the section of wiring I want I also plan to install a timer to keep the power for the windows hot for about thirty seconds after the ignition is turned off. I'll let you know how that goes.

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    Administrator Tom Bryant's Avatar
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    Be sure that the oil on your bell housing isn't coming from the valve covers. I had oil on the rear of my engine and on the power steering cylinder and hoses. Once I fixed the valve cover leaks again and cleaned everything up it's been dry for three years. I was sure the power steering was leaking but it wasn't. I resealed them a few times with RTV. Had no luck with a long lasting fix with that snake oil in a tube. I used cork gaskets once and they were good for about a year before they started showing a little seepage. The last time I used Super Seal blue silicone gaskets with the stainless steel shim in them to hold their shape. These are a permanent fix. They remind me of the old neoprene gaskets I used to buy from NAPA in the '60s. You just put them on dry and they can be used over and over even if you remove your valve covers every weekend to set your clearance on a solid lifter motor before going to the track.

    You should be able to change your pinion seal without removing the differential.

    Since you have the pan off it would be a good time to change the rear main just to be sure. Once you have your rear main cap off take a look at where the seal contacts the crankshaft journal. If there is a grove worn in the surface from the seal you can get a new seal with an offset lip so it will contact on a non worn area. I also highly recommend the Fel Pro one piece oil pan silicone gasket. It comes with retainers that will hold it in place while you install the pan. Just a dab of the supplied sealant at each corner of the front and rear main cap and you are good to go. I will never use a four piece cork gasket again.

    Tom
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

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    Thanks Tom.
    I do plan to use a felpro one piece gasket on the pan and i will be ordering an offset seal for the rear main just incase. I'm almost certain that the vavle covers are not leaking, I will check again just to be sure.

    I've found a few threads (here and on another forum) where people say the pinion seal can be changed on the car. But not one where someone says that they have done it. Would i be better to remove the diff? It certainly would give me more room.

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    Member LLC5's Avatar
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    Always follow a fluid leak to it's highest point, intake manifold gaskets and oil pressure senders and connectors are a common leak area also. Clean the area thoroughly and spray on a white powder (I use K2R with good results) and run the vehicle for a length of time. The fluid leak contacting the white powder residue shows the area of the leak in good detail.
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    Member GTR1999's Avatar
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    Unlike the 63-79 iron diff's, where you can remove the front bracket to get to the pinion yoke, then seal- the 80-82 have a cast in bracket and different pinion seal. I have done the iron seals on the car but never an 80-82. Not saying it can't be done on the car though but it will be tricky.
    Gary
    GTR1999

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    Member GTR1999's Avatar
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    Here are some pictures of what you have. I hate these differentials and won't take them in but these pictures may help you



    Here is the seal in place





    Gary
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    Quote Originally Posted by GTR1999 View Post
    Unlike the 63-79 iron diff's, where you can remove the front bracket to get to the pinion yoke, then seal- the 80-82 have a cast in bracket and different pinion seal. I have done the iron seals on the car but never an 80-82. Not saying it can't be done on the car though but it will be tricky.
    Thanks Gary. This is what I keep hearing. The more I see what is there the more I wonder if it can be done.
    what is the problem with these diffs? Sometimes to do with the housing IIRC.

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    Member GTR1999's Avatar
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    Well I can only offer my opinion on them. Back when new the 80-82 corvettes were slugs, sorry to say. The car was more about cruising then any real performance and GM was gearing up for the C4 production so the concern of the day was to improve mpg and part of that was to cut weight off the car. So they went to the DANA again and what did they gain- 30 lbs over the iron diff more or less. The DANA design was the same small weak pinion with square shoulders, aluminum bearing caps, and a design flaw in the posi where the retainers stick out and get caught. The spiders were smaller, there was no preload crush sleeve, and the case shims are under the pressed on case bearings. Now for most stock applications they work ok, some have pushed 400hp through them and they're still alive, others machine steel caps and swap in a c4 posi but for all that added expense if I wanted a stronger diff I would convert it back to an iron unit, built to application and bolted onto the stock batwing cover. A 12 bolt conversion is not as easy as a bolt it and to be quite frank it more expensive then the value of the car. I have built plenty of iron conversions and they hold up to some abuse.
    Gary
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    Looks like it's not going to be as easy as I hoped.

    The rear main seal is done. I also replaced the battery cables as the lug at the starter looked like half of it was missing. I now have 50mm˛ (similar to 1/0) welding flex to replace that junky aluminium stuff. It only came to $NZ55 for the cable and lugs so well worth it.

    I started to have a look at the diff, and found that the side yoke seals also appear to be leaking. The area around them appears to be wet, and the area below them (which was cleaned up about 2 years ago) is covered in oil and dirt. Oil has also made it only my new composite spring (it only has a few hundred miles on it)
    So now it looks like the diff will need to come out. Not so sure on what I want to do with it now though. I am only running a stock setup (with headers and 2.5" dual exhaust), and don't plan to do to anything more until this engine needs a rebuild/replacement, But whatever I do I would like to keep the E4ME carb on it, so wouldn't do anything to major. I'm thinking that the diff will still hold up fine. I'm thinking just pull the diff and see what it looks like inside before making any decision.
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    20170717_171946_001-jpg

    While I have it off I think I might clean it.
    Did the carrier come from the factory with a coating on it? I seem to think it should be bare aluminium. It seems to have a very think coat of dirt, not sure if there is anything under that.

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    Got The diff opened ind disassembled today after work. I wasn't sure If I was going to do the posi clutch packs or not. Until I opened everything up. Just need to find a new carrier and sort out pricing of a rebuild vs buying a rebuilt unit, or swapping in an older style unit.
    20170720_182257-jpg20170720_165133-jpg20170720_165006-jpg20170720_161958-jpg

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    Quote Originally Posted by GTR1999 View Post
    others machine steel caps and swap in a c4 posi but for all that added expense if I wanted a stronger diff I would convert it back to an iron unit, built to application and bolted onto the stock batwing cover.
    TT913A614
    is this the kind of swap you are referring to? or is this something different again?

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    Member GTR1999's Avatar
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    me, I wouldn't spend a dime or minute on your aluminum diff. I would get a 72-79 iron diff, 1/2 shafts, and brackets. Build that and bolt it to your batwing. It will be stronger then any 80-82 diff.
    Gary
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    Quote Originally Posted by GTR1999 View Post
    me, I wouldn't spend a dime or minute on your aluminum diff. I would get a 72-79 iron diff, 1/2 shafts, and brackets. Build that and bolt it to your batwing. It will be stronger then any 80-82 diff.
    Just found another one of your threads on another forum where you have said the iron cap needs to be made custom to each housing, so I am definitely thinking of just going with an iron unit.
    When you say brackets are you referring to the the strut rod bracket or the spindle flange on the trailing arm?
    in addition to that there's also a possibility that the drive shaft may need to be shortened, and new strut rods (I was thinking about getting adjustable ones anyway)
    anything ive missed? Just trying to get a complete parts list together.

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    Member GTR1999's Avatar
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    You will need to get the front bracket, strut rod bracket, rods, spindle flanges, and possible shorten the Drive shaft. If you are referring to the old CF threads, there are some there I build iron units as well who offer opinions on the build and how it worked out.

    If you build the iron diff like I have outlined in many threads it will hold 400-450hp no problem. The strongest for this conversion would be a super 10, the real one I designed. I have links to that build as well.
    Gary
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